WELCOME to the anvilfire Guru's Den - V. 3.3

THIS is a forum for questions and answers about blacksmithing and general metalworking. Ask the Guru any reasonable question and he or one of his helpers will answer your question, find someone that can, OR research the question for you.

This is an archive of posts from March 22 - 31, 2011 on the Guru's Den
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I was thinking about the possibility of making a hammer with a heavy cam. As the cam turns, the ram comes down until the lobe hits top dead center, then a spring in the ram would allow it to start the upward return. With a big motor turning the cam, just use a pedal to control the speed. How it is geared would also control speed and power.
Just a thought.
   Mike T. - Tuesday, 03/22/11 02:37:33 EDT

Do you flux with borax each time you forge weld layers together for damascus steel
   bluey hocking - Tuesday, 03/22/11 02:42:39 EDT

Iron making. I watched a program the other day about prospecting for gold in Alaska. They were looking to see how thay could seperate the gold from the magnetite. They had a large magnet and would place it in the slurry and large globs of magnetine would stick to it. I was thinking to myself that all that magnetite would sure make some good iron. Apparently where there is black sand,(the ideal place to prospect for gold ) there are also large deposits of magnetite.
   Mike T. - Tuesday, 03/22/11 02:47:26 EDT

PTree: You forgot to cryro-treat the RR spike knife seven times in liquid nitrogen, then dip it in motor oil and do your FINAL quench in liquid oxygen!

People will be talkiing about it for years! ;-)

It's actually springtime on the banks of the Potomac. Back to freezing by Thursday night.

Visit your National Parks: www.nps.gov

Go viking: www.longshipco.org
   Bruce Blackistone (Atli) - Tuesday, 03/22/11 09:13:42 EDT

Fluxing: Bluey, If you are using flux (open welding) then yes, flux as soon as it will start to melt and stick. It also helps to grind the scale off between welds.
   - guru - Tuesday, 03/22/11 11:14:43 EDT

Jock, I think mild steel rr spikes are no longer made. All the spikes on main line or sideings are marked "HC" in this part of Florida. We find a few of the really old spikes that were dug out of the burm. I have permission from the section foreman and the security chief to pick up whatever I want as well as any other rr junk. Spikes become a bit more than a novelty when split and a piece of high carbon steel forge welded in for the blade.
   - Ron Childers - Tuesday, 03/22/11 15:09:54 EDT

Black Sand or Magnetite and Gold: The occurrence of magnetite has nothing to do with where gold is found. However, in placer mining (digging alluvial deposites such as in steam beds and valleys then panning for gold) the iron minerals is considerably heavier than the other minerals and is an indication that you are digging in the deposit where heavier materials settled out and formed deposits. Gold, especially as dust and nugget is very dense compared to other materials so the places where heavy or dense material settled is where you want to look for it. The "black sand" is just a convenient indicator that you are near the right spot.

So, if you have black sand, that is good but does not necessarily mean there is gold. But if you do not have black sand then either you are digging in the wrong place OR there is no black sand. . .
   - guru - Tuesday, 03/22/11 15:39:12 EDT

Mike T: A cam forcing the ram down would not obtain the kind of velocity we get from the various acceleration linkages found in most hammers. It would also be difficult to allow for changes in thickness. Often we are working on a piece that is maybe 1/2 inch thick and need to also be able work the edge that could be 4-5" or use a tool on it that is 4'5" tall.
   - grant - nakedanvil - Tuesday, 03/22/11 16:42:12 EDT

Cam Hammer: Mike, You can use a cam to lift a hammer then let it drop. This is one of the oldest types of hammer. The freedom of the dropping hammer allows for variations in work height. The disadvantage of various drop hammers is the lack of velocity beyond the acceleration of gravity. A spring can increase this a little but nothing like a good power hammer mechanism.


Balanced Spring Helve Hammer by Jock Dempsey
Balanced Spring Helve Hammer


See the archive from February 6th


   - guru - Tuesday, 03/22/11 17:30:22 EDT

Important points about the design above.

1) The counter weight and springs hold the helve above the cam until the operator presses down on the treadle. Thus the driver can run without the helve moving until needed.

This treadle engaged helve is different than other helves because it can be used to hit light or heavy.

2) When the roller drops off the cam it should never strike the low point on the cam. The dies should contact each other OR the work first. Then the cam can gently lift the helve without impact to the mechanism.

3) If the hammer is fairly light (20 - 30 pounds) the treadle spring can be quite heavy and add a lot of velocity to the blow. But if the hammer is heavy (approaching 100 pounds) the force necessary to counter the return spring will be great enough that the machine will become difficult to operate and cause operator fatigue.

Truss helve drawing


4) The helve should have pivots fairly far apart to reduce side to side movement and twisting. The drawing above was made to show how it could be done with fairly light tubing. But heavier would probably be better. The helve could be wood, steel or a combination of the two.

5) This machine has not yet been built. It is an idea that will work but may need some experimentation to get right.
   - guru - Tuesday, 03/22/11 18:03:55 EDT

I am a junior in highschool, and I am planing on going into Astrophysics. Yet I am also looking at blacksmithing as a "profesional hobie" because, frankly, astrophysics can get booring. Can you suggest any mentors, books, and other materials for me? Your help would be appreciated.
   L Ross - Tuesday, 03/22/11 20:35:20 EDT

Mr Ross; you ever get out to visit the Very Large Array in New Mexico; look me up! I'm a bit herder for NRAO on the ALMA project (if you're planning to be an astrophysics person you should know what they are!) I've also been smithing for 30 years and so can give you both a tour of the VLA and of my smithy!

Of course my job may end before you get out here...

Thomas
   Thomas P - Tuesday, 03/22/11 21:01:35 EDT

Thanks for that GURU best regards from TASMANIA
   bluey hocking - Tuesday, 03/22/11 21:06:25 EDT

L Ross,
The above post reminds me of a show I saw one time on the Beverly Hillbillies. Uncle Jed asked Jethro if he had made up his mind on a career. Jethro said, " Well,I can't make up my mind Uncle Jed, I either want to be a brain surgeon or a street car conductor. "
   Mike T. - Wednesday, 03/23/11 00:12:02 EDT

Speaking of using railroad spikes to make knives, the rail should make real good knives. I've seen them drill holes in the side of the rails and they would use a gasoline engine. The drill would turn very slowly and as it cut the metal, they would turn a handle, just like tightening a vise. It seemed like it took 15-20 minutes just to drill through.
   Mike T. - Wednesday, 03/23/11 00:23:03 EDT

Astrophysics and Blacksmithing: There is a surprising amount of cross over between the two fields. For one thing I am constantly telling folks they need to keep up their shop math (mensuration, volumes, density, mass, ratios, geometry and tolerances). Blueprint reading applies to many fields. Then there is shop chemistry and alloying.

I was told about a decade ago by a NASA scientist that metallurgy was still a heat-it and beat-it level technology. At the time they still had a blacksmith on staff and a forging shop for metallurgical research and manufacturing with special alloys and techniques. In virtually all high tech the development of new materials is crucial to advancements.

All that said, blacksmithing is absolutely hands-on. While there is some theory it is pretty basic. When practiced as a hobby there is little or no math. It is a great way to relax and take out your frustrations on something that is hard to hurt while playig with fire. . . But there is a good bit to study and there are many books on the subject. See our (dated) Getting Started article, its links to our book reviews and sword making resources (a good list no matter what you want to make). The Getting Started article is a gateway to others such as the one on Apprenticeships and about schools.

On the other hand, if think a field is boring why would you want to get into it. Astrophysics is a pure science subject where there is little money ad jobs are far and few between. If you can't get excited about searching for mysterious objects among billions, doing spectral analysis of faint specs of light looking for indications of life supporting elements, doing statistical studies of estimated planetary bodies every time there is an advance in data gathering, studying ways to predict events that may never happen in the future of mankind. . . then WHY do it? If you aren't the kind of person that is willing to spend a lifetime advancing science by ONE arcane fact, ONE inapplicable theory or ONE numerical constant, then you probably shouldn't be going into pure science.

Engineering is a similarly math intensive field but it has real world applications making "things", and is much more closely related to blacksmithing. While it doesn't pay like it used to, jobs are much more available and have a wide variety.

   - guru - Wednesday, 03/23/11 00:46:47 EDT

Hello, I have a very nice old 150 lbs. anvil that has gone through a barn fire recently. The barn fire was hot as it melted all aluminum and some copper. I the anvil ruined? Can it be rehardened? It definitely sounds less ringy if you know what I mean.
   Jerry Black - Wednesday, 03/23/11 18:03:41 EDT

Jerry, Barn fires often anneal (soften) anvils but it is hard to tell what is happening in the fire. Then there is the question of how the fire was put out. If the anvil was at a red heat and hosed down by the fire department it may have been rehardened. But this is unlikely.

Generally you can file an anvil but not easily. On a really hard piece of steel a file will "skate" or slip across the surface without cutting. But anvils are generally not this hard and the file will cut but not easily. Note that on most old anvils only the face is hardened, not the horn or the step.

Ring can indicate hardness but the shape of many anvils is tuning fork like and rings well if soft or hard. The ring is more of an indicator of lack of cracks or weld flaws than hardness. A rebound test tells you more but can be subjective.

Generally re-heat treating an anvil will cost as much or more than a good used anvil of similar make. It is also a task that is done in very few places. On old anvils the type of steel and the construction will be unknown and thus the proper method of heat treating will be a question.
   - guru - Wednesday, 03/23/11 19:09:57 EDT

Country Blacksmithing by Charles McRaven describes how he re-hardened an anvil once. Note that it is a hard, hot and tricky thing to do. many folks fail when they don't realize that the quench has to be done with considerable pressure and flowrates---just dumping a hot anvil in a large amount of water won't harden it as the steam blanket will keep it from cooling fast enough to harden.

Thomas
   Thomas P - Wednesday, 03/23/11 19:30:47 EDT

I'm looking for some advice on an anvil I'm constructing. I have used an forklift fork for the construction. I am at a point when I am trying to do some type of hardening to the face. The section that I am attempting to harden is approximately 2" x 5" x 18". It was cut from the upright portion of the fork and after heat treating will be welded onto the the tapered flat portion which will protrude from the front with a small section of a horn. My question concerns the hardening heat and quench. I am not certain as to the type of steel, but after doing some research, I am proceeding under the assumption I am working with 4140. For the sake of ease, will any attempt to air harden this steel work? If I were to get a good soak time and then pull the peice and cool the face with an air compressor, will the sheer mass of the piece prevent me from getting a good hard face? I know that this steel is best oil quenched, but I believe it would be dangerous for me to try and submerge that much steel in a drum full of oil. I really prefer not to use hardfacing electrodes, but will if I must. Is it possible that carburizing this peice would be a better option for me?
   Don - Wednesday, 03/23/11 20:27:15 EDT

Don, Normally 4140 is an oil quench steel. In a section this large you cannot blow enough air to make difference.

You might get away with a water mist spray.

Carburizing also requires a quench to be hard and is VERY shallow, insufficient for an anvil.

4140 is pretty tough and those forks were already heat treated. I would use it as-is.
   - guru - Wednesday, 03/23/11 21:21:32 EDT

For someone starting off I recomment The Backyard Blacksmith: Traditional Techniques for the Modern Smith by Lorelei Sims. Wonderful book. She starts out with the basics, then demonstrates the tools and techniques and, at the end, has about 20 projects to make based on what was in the book. Should still be available at on-line book sellers. Suggestion: Go to www.amazon.com and do a keyword search on blacksmith.
   Ken Scharabok - Wednesday, 03/23/11 21:55:40 EDT

Blacksmiths Depot sells Lorelei's book.
   - guru - Wednesday, 03/23/11 22:43:19 EDT

Don
I built my anvil using a piece of 4140 2"x5"x16"long welded to a new chunk of mainline rr iron and then added a table and horn with weld build up. This was done over a period of a couple months in between jobs so there were many pre-heats and periods of cooldown and actual cold. Anyways without any heat treating or quenching I have a nice ring and 70% bounce back.
   Amos - Thursday, 03/24/11 02:29:02 EDT

I'd go with the current heat treat on a fork lift fork rather than trying to modify it!

Thomas
   Thomas P - Thursday, 03/24/11 11:46:04 EDT

I would like to build a tire hammer. Only I would like to have set plans at least for the hammer mech.
   Tom Johannsen - Thursday, 03/24/11 13:39:32 EDT

Guru, Thank you for the info on the anvil in the fire. My insurance company is replacing everything that was in the fire, I have new replacement. What anvil do you recommend at the 150 lbs. wt.? And where should I be looking? I live near Dayton Ohio.
Thanks Again, Jerry
   Jerry Black - Thursday, 03/24/11 14:14:32 EDT

I'm looking for a nonflame way to solder aluminum cans together. I'd like to work with this metal in a high school art class. What would I need?
   Eric - Thursday, 03/24/11 15:38:05 EDT

Tom Johannsen,

You can buy sets of plans for the tire hammer from Clay Spencer, who also conducts workshops to build the hammers for groups. Write Clay at Clay Spencer, 73 Penniston Private Drive, Somerville, AL 35670, or contact him by email: clay@tirehammer.com
   - Rich - Thursday, 03/24/11 15:50:15 EDT

Aluminum, AL: Eric, Joining aluminum is usually done with relatively high tech welding called TIG or Heli-Arc. Soldering is not usually applicable to aluminum. Both welding and soldering have issues with the natural oxide coating on aluminum that prevents welding and soldering. Welding uses inert gas to shield the surface while a high frequency electric arc breaks through the aluminum oxide on the surface. The high intensity arc is also required to dump a huge amount of energy into the weld zone because the high thermal conductivity of the aluminum rapidly moves the heat from the weld zone.

The best way to work with aluminium cans is mechanical joining or glue. Mechanical joining includes sheet metal screws, machine screws and nuts, pop rivets, wiring, folding. Glues that will work are 5 minute epoxies and hot glue. You could also use construction glue (liquid nails) but it is ugly and messy.

The handiest tool for mechanical joining sheet metal is a hand punch that makes small holes (1/16" to 1/4"). A Roper Whitney #5 Jr. is the most common punch used for this purpose. They sell for about $80 US in set with 6 punches.

But the cheapest way to go is with an ice pick or prick punch, sheet metal screws and a screw driver. Note that both tools here could be considered dangerous weapons in the paranoid North American school environment. Ask both your teacher and school principal about any tools you plan to take to school before doing so.
   - guru - Thursday, 03/24/11 16:23:52 EDT

I've been looking up ways to remove scale and prevent rust spots on some stainless steel spoons I've made (unknown alloy, it was in the bargain bin at my local supplier). When reading about passivation, the descriptions give recipes for a diluted acid (citric, etc.) but they don't mention the starting molarity of the original strength acid.

My wife is a high school chemistry teacher, and although she says she's sure to be overthinking it, she tells me that a 30% solution doesn't mean anything if you don't know the molarity of the acid to start with.

I'm guessing that there's a "standard" for industrial acids.

Can you shed some light on this?
   Bajajoaquin - Thursday, 03/24/11 16:28:33 EDT

Stainless & Rust: First thing to be careful about is to use smooth clean tools (no rust, no scale) when working stainless. If you wire brush it be sure to use a stainless brush that has not been used on carbon steel. Same with grinding belts (clean - no steel use).

As to the strength of the acid solution I'd refer to where you got your directions. With citric I would make a strong solution or near saturated and test it.
   - guru - Thursday, 03/24/11 17:14:43 EDT

Thanks.

Can I infer from the phrase in your last sentence "near saturated" that the starting concentration of an acid would be the strongest that will remain in solution? I.e. a 30% solution is 3 parts fully saturated acid 7 parts distilled water?

The acid solutions I've seen have been from places like the Modern Machine Shop: "20% by vol. nitric acid at 120/140°F (49/60°C) for 30 minutes" (http://www.mmsonline.com/articles/how-to-passivate-stainless-steel-parts).

There doesn't seem to be anything there about the strength of the acid to start.

Other sources, such as The New Edge of the Anvil are similar in the instructions.

Or, looking at it from another direction, could you share a formula for a passivation solution?
   Bajajoaquin - Thursday, 03/24/11 17:27:24 EDT

When a student of mine had his insurance company replace his anvil that had been stolen he presented them with the Catalog from a blacksmithing supply place Catalog and they presented him with a Peddinghaus.

DON'T let them try to fob off a cast iron ASO on you to replace an anvil that was once one of the upper grades!

(Why sending them to a blacksmithing supply is a good idea)

Thomas
   Thomas P - Thursday, 03/24/11 18:01:33 EDT

Citric Acid formulas now give the solution as percent by weight. 10% being recommended for citric acid and 150°F bath for most stainlesses.

Note that chloride contamination can cause a "flash attack" when using citric acid. To help avoid this a wetting agent is recommended (a small amount of detergent such as Dawn dishwashing soap).
   - guru - Thursday, 03/24/11 18:09:05 EDT

I have had pretty good luck using grocery store bought white vingear for pickleing and passivation of SS. I currently have some citric that came to me as a sample and it is listed as 95%. I dil;uted to 50% water and 50% citric and it does a good job as well as a pickle. Have not done any SS since I got the citric.
The white vingear was used at room temp to pickle, and I simply quenched the SS for pasivation. At room temp the vingear takes a couple of days to pickle off heavy scale.
   ptree - Thursday, 03/24/11 19:11:44 EDT

4140 and oil quench - it depends on the size. I spent about 3 years running the quench and temper line as the HT Metallurgist at Crucible Steel in Midland, PA. One of our brad and butter items was quenched and tempered 4140 to ASTM bolting specification sizes from 1/2 " round to 8" round, minimum tempering temperature was 1100 F. 2" round and under we almost always oil quenched (Sometimes with 2", if the Cr and Mo content were low we'd water quench.) Any diameter over 2", we water quenched in an extremely well agitated water quench that was coupled with a heat exchanger to maintain water temp. In the summer, we struggled to keep it below 100 F, which was where we needed it to be. The oil quench was also well agitated, and was heated to maintain a relatively constant temperature.
   - Gavainh - Thursday, 03/24/11 22:10:58 EDT

Insurance Anvil Replacement: The question about replacement depends on what class anvil you started with. While many of the old anvils were top quality and as good or better than what you can generally get today, many were cheaper anvils.

If your anvil is any one of the older forged anvils then the pricier new anvils are a suitable new replacement. But if its one of the cheap cast anvils like a star or Vulcan then many of the available ASO's are as good or better.

Seeing as you are in the heart of the rust belt where used anvils are plentiful I'd collect my money for a new anvil and then buy a good used anvil like you had for aout 1/4 of new price. The rest could go to other blacksmithing tools if that is your thing. OR you could get a shiny new Peddinghaus anvil.
   - guru - Thursday, 03/24/11 22:18:01 EDT

I asked this question over on iforgeiron and was surprised with the answer, so I wanted to double check. I'm ready to heat treat the main flat dies for my homebrewed power hammer. The ram weight is 88 lbs, and the dies are 3" square 4140. After hardening (thanks for the timely tip on quench medium on large 4140, Gavainh!), where do I need to draw the temper to? I was thinking in the 500-600 degree range, but the answer I got was 350-400. I don't want the dies deforming during use, but I also don't want them cracking or chipping and sending out high-speed shrapnel.
   - Stormcrow - Friday, 03/25/11 02:57:58 EDT

Oh, and some new texturing tooling and some texture samples that I made this week: http://helmforge.blogspot.com/2011/03/power-hammer-tooling-and-texture.html
   - Stormcrow - Friday, 03/25/11 03:20:03 EDT

Ptree, if'n you don't mind, where are you buying brand new railroad spikes?
   - Stormcrow - Friday, 03/25/11 03:21:30 EDT

Stormcrow, I get mine from Associated Railroad contractors in south Louisville KY. He has HC only, and will consent to sell a keg or two. None of the other outlets would even return a call about that small a quantity.
Depending on your location Birmingham Spike in Alabama said they would ship to me in keg lots, but the very nice and helpful lady there suggested I try Associated as I could pick up.

On thinking, since I am just arriving at work, let me check this evening and I will confirm the name and give further contact as well.
   ptree - Friday, 03/25/11 07:37:40 EDT

Hammer Dies: Stormcrow, the steel used and the heat treat are somewhat shape dependent on power hammer dies.

1) 4140 is an OK die steel but is not recommended for radical shaped dies such as narrow fullering, crown and so on. All those fancy relatively aggressive dies and dies used for cold work that Big BLU sells are made of carefully heat treated S7. Early Big BLU dies were 4140.

2) Fully hardened 4140 ranges from 54 to 59 HRC. But it should be tempered for any heavy use.

3) Tempering recommendations from the ASM heat treaters guide for 4140-4142 is a minimum of 400°F. This leaves near full hardness. The following is extrapolated from a hardness graph given in Brinell Hardness with nearest points taken from a conversion table for Rockwell hardness. Tensile values are generic, not specifically for 4140. All data is +/- 10% as read at best and conversion tables rarely agree on Brinell to Rockwell. (HB = Bhn)
SAE 4140 Steel Tempering
Tempering
Temperature
Hardness
Brinell
Hardness
Rockwell
Tensile
400°F 200°C 514 HB 55 HRc 297 KSI
500°F 260°C 477 HB 50 HRc 243 KSI
550°F 290°C 461 HB 48 HRc 235 KSI
600°F 320°C 444 HB 47 HRc 225 KSI
650°F 340°C 429 HB 46 HRc 217 KSI
700°F 370°C 415 HB 44 HRc 210 KSI
800°F 430°C 363 HB 39 HRc 182 KSI
900°F 480°C 331 HB 36 HRc 166 KSI
1000°F 540°C 293 HB 31 HRc 145 KSI

The ASM Handbook on forging recommends 6G and 6F2 (??) steels for large dies and 4150 for small dies (4370 for higher carbon dies). In this case "small" is probably 300 pounds or less. . . Small die hardness in 4150 is recommended at only 277 to 321 BHn. In our small shops with hammer sizes of 50 to 150 pounds dies are generally harder. Note that S7 is in the same carbon range as 4150.

So, your initial thought was right. Note that Rockwell 44-45 is just barely in the machinable range and that a grade of H13 is sold in this condition to avoid heat treatment after machining. This saves a lot of trouble in small shops. I have seen corner impact chip this steel. Corners should be rounded. . .

The 350-400°F value commonly given is a MINIMUM starting point for almost all steels so is a safe answer but non specific. I often use this value but qualify it as a minimum AND because it can be achieved in a kitchen oven. It is recommended that you temper immediately after hardening and before the steel reaches room temperature to avoid cracking. But you can always re-temper to a higher temperature - so a minimum temper is a good start if you do not know what your final temper should be.

Grant Sarver makes a lot of his tools such as clapper dies from 4140 but I do not know the heat treat.



The one thing I do not like about the Heat Treaters Guide is that the data, collected from many sources is not given in a uniform form. Charts on the same page will give Rockwell and Brinell hardness.

Hardness Conversion Table

Temper Color Chart with sample steels
   - guru - Friday, 03/25/11 09:45:37 EDT

Hello Guru,

I was curious to know is it possible to cast a finished 440 stainless steel dagger's blade into melted copper?

If so would, the blade is doubled edged would it the copper casting dull the sharpness of the blade?

Thanks,

Daniel Ra
   Daniel - Friday, 03/25/11 08:22:45 EDT

Stainless and Copper: Daniel, I am not sure what you are trying to ask.

If you are trying to cast a grip or handle around the tang of a stainless blade without ruining the temper (hardness) then probably not. The melting point for copper is well above the tempering temperature for blades made of 440 stainless. It would result in a hardness less than 43 HRc which is OK for the tang but probably too soft for the blade. The pouring point of most metals is considerably higher than the melting point.

It MIGHT be possible to do what I think you want by using a heat sink to keep the blade cool beyond the tang. However, to get a good casting some of the blade is going to be overheated.

To encase the blade with copper or to make decorative slabs on the sides of the blade probably would not work.

It is common on cheap "wall hanger" swords to cast a zinc handle directly on the blade. The difference is that the zinc melting point is about half of copper and the pouring point considerably less as well. We are also talking about a product that is usually NOT a hardenable grade of stainless so there are no concerns about ruining the blade.
   - guru - Friday, 03/25/11 10:09:03 EDT

Daniel

How about electroplating the dagger. As far as molding a handle for a knife, I received samples of plastic used in silicon molds. The company told me I could make a silicon mold of an exotic antler or horn, pour the plastic in the mold with the appropriate coloring and duplicate the antler-horn. I don't know why the tang couldn't be run into the mold and the handle just molded around it.
   Mike T. - Friday, 03/25/11 11:14:00 EDT

Insurance and Anvils: My student had "renters replacement insurance" for his old worn "farm anvils", cast iron! The insurance replaced them with Peddinghaus---because they didn't know where to source anvils and so the cost of going with a top of the line product from a catalog they could easily reference was less than spending the time tracking down a more even match. (probably got a commendation for being able to close the case so fast)

I know about all of this as I had to attest in writing that he had had the said anvils and they had been stolen. (and then put up with the gloating over his new anvils, sigh)

Thomas
   Thomas P - Friday, 03/25/11 13:08:01 EDT

Insurance and replacement costs are a peculiar thing. I had a relatively new camera and an old laptop stolen. A new replacement for the camera in nearly the same model cost half of the original but the laptop replacement was maybe 20x what I paid/traded for on the old one. I was happy and the insurance company did the only thing they could.

On the other hand you almost never come out even on used automobiles. Right now my 15 year old van is valued at only about $1000. But to find a replacement in similar condition would cost at least $5000. Same with my old truck. I paid $1000 for it and have invested another $3000 in it and need to put another $1000 in it. I MIGHT be able to sell it for what I have in it but finding a replacement at insurance value would be very difficult to impossible.
   - guru - Friday, 03/25/11 13:41:14 EDT

Guru: Does the below statement mean that Fisher anvils are ASOs as well? They have cast bodies and crucible steel face plates (only thicker) just like the Vulcan anvils? The star anvil just have chilled faces, so I understand concerning those.

Guru wrote "If your anvil is any one of the older forged anvils then the pricier new anvils are a suitable new replacement. But if its one of the cheap cast anvils like a star or Vulcan then many of the available ASO's are as good or better."
   - Huckleberry - Friday, 03/25/11 14:25:56 EDT

Fisher Norris Anvils are the original steel faced cast iron body anvil. They had the original patent and made a good product. The face was plenty thick and the part extending out on the horn created an all steel tip. Fishers are a good anvil and still sought after due to being a "quiet" anvil. When new they sold for less than forged anvils of the time.

Other manufacturers made anvils by the same process after the Fisher's patent ran out. The process is not fool proof and the other makers cheapened the product as well as doing a poor job in many cases. The cheapening included using faces as thin as 1/4" where 5/8" was necessary. Shapes were made heavy and cludgy to support the thin pages. These anvils are not much better than a plain cast iron ASO and their new prices reflected it at the time.

In the 19th century and early 20th century many retailers sold anvils and they had a range of quality honestly reflected in the prices. The problem today is that cast iron ASO's are sold with claims of being "professional, high quality, "steel" . . . Iron maybe, low carbon un-heat treated ductile iron sometimes, but not steel. Its a buyer beware world.
   - guru - Friday, 03/25/11 15:53:26 EDT

Thanks, guru. I'll look at the color chart again and pick were to put it. Given the amount of force on it, I'm guessing a bit harder, so in the lower 500 range. I'm seeing a bit of deformation on one of my pairs of railroad track dies.
   - Stormcrow - Friday, 03/25/11 18:09:05 EDT

Stormcrow: one of the reasons for using a higher alloy (4340, S-7, etc) than 4140 is quench reliability. While large 4140 rounds can be water-quenched, squares are a different story. Each corner of a die is a three-sided pyramid and in quenching the corners will cool very quickly, often causing "finger-nail" cracking of the corners. That is the main reason for switching to an alloy that will give good results by oil quenching. If your dies survived the water-quench then you're good to go.
   - grant - nakedanvil - Friday, 03/25/11 18:52:37 EDT

Thanks Guru
   - Huckleberry - Friday, 03/25/11 19:22:12 EDT

4140 - Good reason to knock off those corners as much as possible before hardening. But dovetails add more, and sharper, corners that cannot be but so round.
   - guru - Friday, 03/25/11 20:27:46 EDT

I would like to forge some oak leaves. Any advice or demonstration sites you would recommend? Thanks! RG.
   RG - Friday, 03/25/11 22:13:25 EDT

Oak Leaves: RG, Oak leaves start with an appropriate blank. Trace your favorite leaf sample, use on size or enlarged. I've seen some nice oversized leaves over a foot long. I would probably draw my own but everyone has different skill levels. Make the stem about 1/2" to 5/8" wide and plenty long. This can be rolled up and forged into solid OR wrapped around a tapered bar and forge welded on.

To use with forge work 1/8 to 3/16" (3 to 5 mm) plate works well and oversize leaves easier to work with. Today most folks plasma cut such blanks to get a clean cut but it can be done with oxy-fuel and ground to clean up. If you are making a tree's worth then your patterns needs to be produced in CAD, converted to DXF and cut by a production house. I would make three variations in size/shape.

Your blanks are then worked hot. A fold down the center slightly hammered then opened back up will have a permanent crease. If you want a high rib clamp the edge in a vise when you open it up. Side vein creases are worked hot on a wood block or special made support swage. This is a good job for a helper or on a treadle hammer but can be done alone. A pivoting creasing tool works.

After creasing and rolling the stem then hammer the edges out a little thinner. The extra material will force the leaf to warp and wrinkle the way an oak leaf does. You may need to consider the thinning and widening in your blank design. Then working on a wood block (or the anvil horn, swage block. . .) with a ball pien hammer give it some curls.

The stems can be forge welded or arc welded and blended in, preferably by forging. Grinding always shows and rarely looks like part of the work. Have fun!
   - guru - Friday, 03/25/11 23:09:10 EDT

Michael Walker Making Oak Leaves at Dan Boone's Hammerfest 2000.
   - guru - Friday, 03/25/11 23:20:12 EDT

I was wondering if there was some reason I couldn't just get http://www.magidglove.com/Magid-Zetex-ZT1314WL-High-Temperature-Safety-Gloves-ZT1314WL.aspx?DepartmentId=197
instead of tongs. They're rated to 1100 F, and I'm not planning on doing any welding. Thanks!
   Baruch - Saturday, 03/26/11 00:13:44 EDT

Baruch, Smiths hold "long" pieces in their bare hands. But long is proportional. In small 1/4" stock one foot is long enough to hold bare handed. In 1/2" it needs to be two feet or more. In a gas forge you usually need longer pieces for bare hand work than in a coal forge.

But pieces like that 12" length can become 6" or less when the ends are curled up into an S hook. If you heat the middle for twisting the hook is being held 3" from the 2,500°F heat.

Now, those gloves are resistant to 1100°F but that DOES NOT mean you can handle things that temperature with them. The inside of the glove will rapidly reach a significant proportion of the external temperature. There is no "magic" to them. They are not insulated any better than the kitchen cooking mitts. Probably not as well. You can pick up relatively hot low mass items with them for a very short time.

1100°F is right at the limit for what smiths call a "black heat". You cannot see the heat. It is not hot enough to work the iron. But it is very hot to organic life. Our normal working temperatures are well above a black heat. This means that short pieces that are red or yellow on one end are at a high black heat on the other. Far too hot for gloves.

Use pliers, make or buy tongs. Learn to use them. It is an absolutely essential manual skill.

Smiths often wear light knit Kevlar gloves to prevent getting burns from accidental slips and touches on hot iron. However, all these are is a little extra protection, not a replacement for tongs.
   - guru - Saturday, 03/26/11 02:23:05 EDT

Thanks for answering my questions about copper plating my modern dagger yesterday.

Do anyone have a recommendation of where or who to go to so I can have it done?

Thanks,

Daniel Ra
   Daniel Ra - Saturday, 03/26/11 07:02:25 EDT

Thanks for answering my questions about copper plating my modern dagger yesterday.

Do anyone have a recommendation of where or who to go to so I can have it done?

Thanks,

Daniel Ra
   - Daniel Ra - Saturday, 03/26/11 07:04:59 EDT

I HAVE SOLID BOX BLACKSMITH VICE 5.25 INCH JAW 75 POUNDS IN EXCELLENT CONDITION. IT IS STAMPED W.T.& F. C o
THE C o MIGHT BE A C . BUT IT MIGHT ALSO MEAN COMPANY.
DOES ANYONE HAVE A CLUE AS TO WHO MADE IT????
   JOHN L. - Saturday, 03/26/11 12:14:55 EDT

Grant - So in that case, would it be better for me to go with quenching in oil, not getting it so hard but also not risking cracking as much? Or will rounded corners be sufficient for a water quench? What is the difference between 4340 and 4140 in terms of heat treatment and performance?

Guru, my dies don't have dovetails; they're welded to base plates.
   - Stormcrow - Saturday, 03/26/11 12:20:09 EDT

4140 Again: The oil quench is recommended in the ASM Heat Treater's Guide for all sizes. The steel will get fully hard on the outside but the center may not fully harden. I do not see this as an issue in a big rectangular die.

Water quench as suggested by Gavinah should be tested. That is the problem with one off jobs. . . The Guide has all kinds of graphs with hardness depths and so on. But other than cylinders there is not much about variations in shape. I have seen a number of places listing this steel as 4140-42 which means either the chemistry is not tightly controlled OR their inventory has both sold as the same product. The Guide lists the two as different with variations in treatment and results. As Gavinah stated they used different quenches depending on the exact chemistry of what was being processed. So everything is not always equal. . .

Rounding the corners before heat treatment is a good idea no matter what. As Grant pointed out those outside corners with three vertexes are the first thing that is going to quench and much faster than the rest. Uneven rate of cooling is the primary reason for the stresses that result in cracking. The ideal shape would be a sphere. . . So, the more corner you can take off of a cube the better.
   - guru - Saturday, 03/26/11 15:29:29 EDT

Guru, you mentioned kevlar gloves....where can I find some that aren't "fuzzy"???? Presently I use Costco thin leather and I'm getting a nice collection of unused right handed ones,LOL.
   Thumper - Saturday, 03/26/11 15:33:13 EDT

Thumper, All of the industrial glove compainies such as Memphis Glove make knit kevlar. These are usually sold as singles and fit either hand. They come in many weights and the heavier the weight the beter the protection for small scale. The light weight kevlar string knits will have siginificant open space in the weave and let smnall scale right through. These light weight string knits are more for cut resistance the heat.
What you should look for are medium or heavy weight string knit Kevlar. Expect to pay in the $3 to $7 each.
For forging, I prefer leather palm gloves. These have a chrome leather palm and fingers with a canvas back and cuff. Good cut, abrasion and scale resistance. Not much heat from a big hunk of steel, but enough for you to drop the steel and pull off the glove without a real burn.
I buy these by the dozen at about $).85 to $1.15 a pair.
ptree the industrial safety guy:)
   ptree - Saturday, 03/26/11 17:52:55 EDT

Blacksmiths Depot sells a variety of gloves in singles or pairs

When I wear gloves in the shop I use the gloves PTree mentions (common cloth and leather work gloves). I use them for anything I need gloves for in the shop, welding, schleping stock or lumber. . .
   - guru - Saturday, 03/26/11 18:15:42 EDT

John L.
It is probably Warren Tool and Forge Co., Warren, Ohio. Their tools were sometimes marked QUIKWERK. They acquired "IRON CITY" brand tools (Pittsburgh) in 1958. Iron City was a manufacturer of leg vises and other tools.
   Frank Turley - Saturday, 03/26/11 18:51:41 EDT

Wood basically is a series of fibrous annular rings forming tubes. Why is it that when it burns that it transforms into crystalline shapes of carbon? I assume that the ash may be the same giving it some of it's abrasion. Something I have watched all my life and have taken for granted...what's up with rapid oxidation?
I have also realized that "perpetual motion" is only temporary.
   S K SMith - Sunday, 03/27/11 12:55:44 EDT

Temporary perpetual motion is an oxymoron.

The cellular structure of the wood is still in the charcoal. I think any time carbon is not part of a compound it is crystalline. But when you hang a bunch of hydrogens and oxygens on a carbon atom it can no longer align in crystalline form. Interestingly the natural state for many carbon compounds is proteins which due to a natural "kink" in the molecules always arrange in spirals when joined. We know these as RNA and DNA.

Rapid oxidation compared to what? Under what circumstances? The more oxygen or the more oxygen rich the atmosphere the faster things burn.

   - guru - Sunday, 03/27/11 13:29:03 EDT

I was watching How It's Made on TV and saw something pretty interesting. They were making bolts and during the tempering process, they had flames coming up, they remarked that the flames were not part of the tempering process, but to prevent scale on the bolts. I thought to myself, is it possible that the flames were burning off the oxygen ? I don't know what the source of fuel was, any ideas ?
   Mike T. - Sunday, 03/27/11 14:28:12 EDT

Mike it makes sense and is probably cheaper than other methods. Burners (gas or oil) with no mixers or adjusted to produce a carburizing flame will absorb oxygen in the space around the parts.
   - guru - Sunday, 03/27/11 15:33:14 EDT

I have a very old pair of pliers in good condition labeled "Snap Lock" #1607 mfg. by Semour Smith & Sons, Oak Ville, Conn. There is no patent date.

They look just like Vice Grip pliers, could they be the originals ??
   Carver Jake - Sunday, 03/27/11 17:11:33 EDT

OK let me rephrase. When round wood burns much of it will change into squarish shaped cubes. Why?
Deep thoughts: I think during our short little life spans perpetual motion does exist in life forms like plants which might be able to be stretched into a quasi-mechanical definition. However that is still in a temporary climate. I like oxymorons. A stiff wind.
   S K SMith - Sunday, 03/27/11 17:27:18 EDT

SK, When the organic matter sh5inks from the outside in cracks form. But this is not true with all charcoal. These "cubes" are not crystals, just convienient strss crack locations. . .
   - guru - Sunday, 03/27/11 17:34:53 EDT

Vise-Grips:
   - guru - Sunday, 03/27/11 17:38:51 EDT

OK I got it..thanks. The cubes are formed by shrinkage from heat, that's cool. I can't stop.
   S K SMith - Sunday, 03/27/11 17:41:32 EDT

Mike T. I have seen that How Its made. Many of their narratives are a little off. That flame at the entrance of the furnace is a standard flame curtain. The purpose is to burn off any leaking gas, as it leaks, before a big cloud forms. Most controlled atmosphere furnaces use argon, or nitrogen or some combo to prevent scale. We had radiant tube heaters in our controlled atmosphere furnaces. These had the combustion from natural gas and regular atmosphere inside the tubes and the tubes would radiate the heat into the furnace chamber. The chamber had a constant nitrogen purge, And a flame curtain at both doors.
   ptree - Sunday, 03/27/11 18:43:35 EDT

Popular Television, particularly the History Channel and many of the specialized cable shows almost always get something noticeably wrong in their facts in almost every show. The surprise is that one of the the most sensational shows, Myth Busters, get their science and technology right more often than the less sensational "fact based" shows. Besides, they blow things up every chance they get.
   - guru - Sunday, 03/27/11 19:51:43 EDT

Another thing that caught my attention on How It's Made was the forging of the hexagon heads on the bolts. They placed the round bolt blank in a coil that used electricity to heat it up. It heated it up very quickly to over 2000 degrees ( just before molten ) then placed the bolt in a powerful punch ( die ) that formed the head in one motion. You couldn't call it a hammer, because it was just one quick punch. What came to my mind was this...How practical would it be to build a coil, heat it with electricity, place a knife blade in it and heat it and forge it ? No scale from an open flame.
   Mike T. - Sunday, 03/27/11 23:29:01 EDT

Mike T: What You saw is an induction heater. It is a great idea if all the parts You are making fit into the same or a few coils. The reduction in scale comes from the short time at heat. A reducing flame doesn't make scale, but as soon as You take the work out into the air, the scale starts to form.

Grant Sarver sells suitable induction unit for knife forging, if You wanted to go that rout. Initial cost is farly high, but it is fast, and can be cost effective in a production setting.
   - Dave Boyer - Sunday, 03/27/11 23:47:00 EDT

Mike T: A little more detail. The electricity is high frequency high amperage AC, the power unit is an inverter, too complicated to make at home, and not cheap to manufacture. The frequency is ajusted according to the size of the work. The coil is copper tube with cooling water going through it. This is entirely different than an ordinary electric stove burner, which operates on resistance.
   - Dave Boyer - Sunday, 03/27/11 23:53:58 EDT

Dave,

Thank you for the information. You learn something new everyday, I think I would like the induction unit. I will contact Mr. Sarver.
   Mike T. - Sunday, 03/27/11 23:59:36 EDT

Mike T. - If you poke around Youtube you can find a number of videos showing the induction forges in action, including Grant (look for "nakedanvil") using them in a production capacity to manufacture blacksmithing tools.
   - Stormcrow - Monday, 03/28/11 02:28:04 EDT

Mike T. Induction heating has been around since at least the '40s. Properly tuned for frequency and times, you can heat a billet through, or get surface heating for hardening. Cam and crankshafts are good examples of hardening performed by induction. In many cases the cam or crank is induction heated through, forged, machined and then induction hardened followed by precision grinding of the bearing surfaces. Axles are also made the same way. In the average automobile there are several hundred items made with induction heating.
   ptree - Monday, 03/28/11 07:36:52 EDT

Weather Report: Here it is, almost April, the flowers in Sherie's garden are blooming, we are looking for the humming birds that should arrive soon and at 8:30am EST this morning in Boonville, NC it is 37°F, snowing and sticking to the ground! On surfaces raised off the ground there is a 1/2" accumulation.
   - guru - Monday, 03/28/11 09:08:12 EDT

My shop is in oakville CT I just googled it an it seems the semour smith and sons building was with in a block of my shop (in the old pin shop building) that is kind of cool.
MP
   mpmetal - Monday, 03/28/11 09:08:18 EDT

In the 1960's, a "Lever Wrench" plier came on the market. They were a self adjusting locking pliers. The company was a flash in the pan; didn't last long.
   Frank Turley - Monday, 03/28/11 09:34:23 EDT

Induction Forge in the anvilfire NEWS. At the time Blacksmiths Depot was selling them for Grant Sarver but dropped them. I think sales were too slow for them.

The entire outfit was selling for over $4,000 at the time. So you REALLY needed it. An American made unit costs over twice that amount. But there are some tremendous advantages. Among them:

1) No fire, flames or exhaust fumes.
2) No waste heat raising shop temperatures.
3) Very controlled focused heat.
4) Very fast. So fast you do not need multiple pieces heating.
5) Low scaling due to the fast heating.
6) Energy efficient - 90% or more of the energy goes into the work. A small amount of radiant heat from the work must be removed from the water cooled coils and there is a little loss from the electronics. Compare this to a traditional forge where probably 90% of your fuel energy is wasted. . . While this is great to heat your shop in the winter it is very wasteful the rest of the year.

Induction heaters are used for almost every application whee steel needs to be heated including heat treating.
   - guru - Monday, 03/28/11 09:42:32 EDT

When I was a kid, I had an electric train with a transformer that provided electrictity to the tracks. Being one to experiment, I would attach a paper clip from one terminal of the transformer to the other. The result was that the paper clip would get red hot. I guess an induction unit works about the same way.
   Mike T. - Monday, 03/28/11 12:26:27 EDT

Mike, that is resistance heating or a dead short. It is NOT the same as induction heating.

In induction heating a strong high frequency magnetic field is created. When a piece of iron is in this field the rapidly changing magnetic field heats the metal. The piece is NOT directly in the electrical circuit. Most of the heat is in the work piece, not the wires leading to it. Most of the heat in the coils is from radiant heat from the work piece.

In many industrial applications the induction coils are embedded in ceramic or refractory. The heat is created in the steel inside the furnace, not from the coils.
   - guru - Monday, 03/28/11 12:51:30 EDT

One major issue with induction forge: once a piece is forge into something like a scroll or other non-linear form it cannot be put back into the coils for further forging... better be good at forming stuff in one heat or you're screwed.
   - Nippulini - Monday, 03/28/11 13:10:40 EDT

Guru, your post of 3-27 was interrupted re: my vice grip pliers and did not go through. Any info?

Thanks Frank for your input, I had some of those automatic pliers.
   Carver Jake - Monday, 03/28/11 13:14:30 EDT

Jake, Its just a link to the Vise-Grips article.

Induction Coil Limitations:

You can say the same thing about a gas forge. Many that you can heat a 1" bar will not accept the forged results for a second heat (usually when using a power hammer).

But as Grant also shows in the photo of heating just the edge of a blade to harden it, the "coils" do not need to be circular. And many systems use loops where the part is heated from one side. A surrounding coil is more efficient and heats more evenly but a side loop will take a scroll as long as it is on one plane. Surface heat treating systems use a loop and "scan" it across the surface.

Induction heaters are a high production tool where you are generally making a LOT of something. That is most often done in dies or bending jigs where you do everything or most of a job in one heat.

When you change from a typical coal forge to a gas forge you suddenly find that you can evenly heat way more bars than one man can forge. So you add a power hammer to your shop. These work well together when doing open die and free hand forging. But as soon as you start production work in dies (either on the hammer or in a press) the gas forge needs to be larger OR faster heats are needed, and the induction forge often meets than demand.
   - guru - Monday, 03/28/11 13:52:53 EDT

In forgeing billets for closed die work, we used circular pattern tunnel induction forges. These had a coil sort of like a coil spring, embedded in insulation and had water cooled stainless steel tube rails. The billets were placed on the rails and on a timer, the next billet was pushed into the coil and the oldest one exited to be forged or rejected if not ready to forge. Many of the billets we forged were 4" diameter by 12" long and the coil would be perhaps 8' long. Residence time was probably about 6 to 7 minutes. In the bigger diameter parts it takes longer to get the heat to the center without burning off the od, since skin effect heats the OD the most. The advantage is very uniform heat, in very high volume. You use way less energy, and generate way less employee sapping heat. You still have the radiant heat and the cooling forgings. You also have a cooling tower moving water through 6 or 8" headers to cool the coils and electronics.

In the axle shop we were still running a natural gas forge, heating big billits when I started. heated about 4 foot of a 7' long billet, by sticking the billet through a water cooled water front. Held 20 or so billets, and once the forge was hot the billets would be at heat in about an hour. As a billet was pulled a cold billet was replaced. Once the first 20 had been forged, then another 20 minutes or so was required to fully heat the billets. Now this forge fed natural gas thru 3/4" orifices at 20 psi. Not inches of water column 20 PSI! And there were 6 burners each with that 3/4 orifice.
Replaced with a single coil, took about 6 minutes for a billet to heat, and that matched the cycle perfectly.
Oh and by the way, even taking out for the added electricity cost, we saved $20,000 per month when that gas forge was turned off.

Many of the smaller axles were run on a conveyor through a C tunnel and never heated more than say 20" of a 6' billet. That way the rest of the billet was much less likely to distort in an upsetter.

Like all things in engineering every choice is a compromise. The induction vs gas vs coal. Each has +/-.
   ptree - Monday, 03/28/11 14:32:27 EDT

I'm also cross-posting on I Forge Iron, I hope nobody minds. But I thought that, since asking kind of open ended, I'd try to do some follow-up here, too.

After checking out these replies, and others, I think I've figured it out. One of the issues was that I was always thinking of acids as being liquids, but citric acid is a solid, so "pure" citric acid doesn't make sense as a bath, or as a 100% solution.

So the percent solution thing comes in two different forms:

1) Liquid acids (hydrochloric, sulfuric, etc.), otherwise known as a miscible acid. A 100% solution is just pure acid. The confusion was coming in that you can also describe the strength of the acid in terms of molarity (moles per liter of solution). So, according to the chart Jack provided, phosphoric acid is at 100% at 17.3 moles/liter. My wife was working with acids using molarity, and I was asking in terms of percent solutions.

2) Solid acids (citric). For these, the solution is figured as percentage by weight. A certain number of grams per liter. In this case, you may not get to a 100% solution, since there will be limits on solubility.
   Bajajoaquin - Monday, 03/28/11 14:42:22 EDT

While induction is nice for production, once you have one you find it incredibly convenient at the anvil. Easy to get a juicey white heat right where you want it and the machine can be right next to the anvil - no walking back and forth. While a gas forge will heat the shop in the winter, carbon monoxide can build up fast, so then ya gotta open the doors. Gas forge also heats the shop in summer, I get twice as much work done in the summer with induction. And yes, energy cost is about 10% compared to gas. Coil can also be in the shape of a cinnamon roll.

There's a Mark Aspery video on Youtube showing Darryl Nelson working on an animal head. With induction he can heat the near-finished head without the detail parts over-heating. He also works on one head while keeping it clamped in the vise using an extension flexible "wand".
   grant - nakedanvil - Monday, 03/28/11 15:01:45 EDT

Well now that the forge extension is nearing completion---I mounted the cross beam for the front doors over the weekend---it looks like my nightmare might be true.

Just got word that the project plans to go to about 1/2 the current head count over the next couple of years.

Anybody need a UNIX based software tester/Geologist with a BS in each?

Thomas
   Thomas P - Monday, 03/28/11 15:03:33 EDT

I have to correct the Guru on one point. The induction machines I sell are 10% of what new American made machines cost. They are made in China and in the five years I've been selling them I've had nearly zero problems. I have more than 100 machines in the hands of blacksmiths and knife makers and many more industrial installations running all day, every day.
   grant - nakedanvil - Monday, 03/28/11 15:21:12 EDT

Thomas, it may be time you learned to make a living from your hobby. . .

Citric Acid. . . knowing the form helps, that is why I was confused by your question. I gave the right answer but you were confused by the "saturated" solution. Yes it is a white powder and dry food stuffs often have a considerable amount. Remember "Tang", "the stuff astronauts drink". A large part citric acid, sugar and a little flavoring. Just add water.
   - guru - Monday, 03/28/11 15:27:19 EDT

Grant, one of our Google advertisers, an American manufacturer whom I spoke to, sells a machine similar to yours for $10,000. If yours are down to $1,000 I'll take TWO today!
   - guru - Monday, 03/28/11 15:33:33 EDT

Guru, as an insulin dependent diabetic I *HAVE* to have health insurance.

Thomas
   Thomas P - Monday, 03/28/11 15:47:42 EDT

If I understand what you are saying about induction coils, they work similarly to a microwave oven. I think microwaves move the atoms in the food rapidly back and forth producing internal heat. The induction coils produce a magnetic field that moves the atoms in the steel back and forth producing internal heat ?
   Mike T. - Monday, 03/28/11 16:04:11 EDT

Lets make sure we compare apples to apples. Is that a 15KW machine? Does it come with a cooler? You were quoting my machine with cooler ($700.00 extra). The 15KW machine I sell is $2,995.00. Got a link? The domestic ones I've seen at that price were like 3KW.
   grant - nakedanvil - Monday, 03/28/11 16:15:43 EDT

Here's a video showing what I beleive is an induction forge being used in a production setting, making Wetterlings axes: http://www.youtube.com/watch?v=qdwZnuX8nBU You can see it just before the four minute mark. That's a pretty funky hammer they're using, too.

Actually, there are quite a few different videos on Youtube showing the induction forge in use. Do a search and you'll see.
   - Stormcrow - Monday, 03/28/11 16:17:24 EDT

Tocco/Inductotherm was demonstrating a little induction unit to blacksmiths a couple years ago. It was 3 or so KW and heated a 1/2" bar to a bright red in a minute or so. The machine I sell will bring 1/2" to yellow in 15 seconds and melt it in two in 20 seconds. Many of these manufacturers have a rather poor understanding of what a blacksmith needs. They seem to think we heat a small piece to dull red and beat on it for a couple minutes.

Oh yeah, At the time that machine was $20,000.00!
   grant - nakedanvil - Monday, 03/28/11 16:31:29 EDT

This may be a dumb question but I'll ask it anyway. When steel is brought to a white heat, is there an infrared spectrum that requires eye protection ?
   Mike T. - Monday, 03/28/11 17:11:41 EDT

Guru,

Yes, it was your response about percentages by weight that made the bell go off for me. That's when I was able to put together all the things I'd been reading.

Thanks for the replies.
   Bajajoaquin - Monday, 03/28/11 18:15:36 EDT

Thank you Jock, for sparking me to do some (self-enlightened) research. There only seem to be three American manufacturer of induction equipment suitable for blacksmithing/forging. That would be Inductotherm/Raydyne, Ajax/Tocco and Ameritherm. None of those seem to offer what you are referring to. Other "American" sources all appear to be re-branding Chinese equipment and taking a whole lot more mark-up than I do. I really would like more information on the one you are referring to.
   grant - nakedanvil - Monday, 03/28/11 19:43:12 EDT

Grant, I am not positive on the specifics. It was over a year ago when I spoke to the fellow. He called me wanting to know if I would like to handle his machines. It was a pretty short conversation. Also can't remember the name but DID see it on one of our google ads as the other day. . I don't think it was Inductotherm. I mostly remember it was running in an odd place (you can never figure google OR the key words some folks use for their ads).


Its against the rules for ME to click on the google ads. If I want to follow a lead I have to copy the link and go to it without the tracking numbers. . . Its a pain so I rarely do it unless I think its an ad that shouldn't be running here OR something I'm really interested in at the moment.

Wetterlings Axe Video I think that is a Toggle Press being used for the finishing the forging. They don't show the Notice the different possitions for each part of the taper. The press doesn't work so much like a hammer. It always goes so far and returns. I would have liked to see them punch the eye.
   - guru - Monday, 03/28/11 20:45:08 EDT

I would have loved to see the eye punched as well. I think it's a pretty nifty layout, though you'd have to have a pretty large monetary investment to set it up initially. 'Course I do have a poorboy mentality about things...
   - Stormcrow - Monday, 03/28/11 20:49:35 EDT

Thomas; jobs:

This is probably a bad time to go Federal (what with them folks on the hill still arguing over this year's budget and threatening to pull the plug on both the government and the debt) but check out http://www.usajobs.gov/ for both jobs in your area of expertise, and the area of your interest.

There are a number of NPS sites that use blacksmiths as interpretive rangers. The jobs are rare, but they do come open from time to time. If you spot anything interesting, contact me and I can at least give you some background. (That's the NPS jobs, not fed. bit-pusher jobs. ;-) If you see anything in DOE, DVA or GAO, let me know and I can check with friends or family.

Check the site every week or so; there is a constant turnover.

Good luck.
   Bruce Blackistone (Atli) - Monday, 03/28/11 21:15:07 EDT

Induction equipment in the US.
Having visited the main office and factory for Inductoheat, and in the old days Tocco, and American Induction Heating, all up in Detroit area, (Think Sterling Heights, I can offer this.
Look at the address for each company, and figure how many US makers there now are:)
   ptree - Monday, 03/28/11 21:22:16 EDT

By the way, the hammer dies are taking a nice, relaxing seven hour soak at 540 degrees in my kiln right now. Thank you, gentlemen, for your help on heat treating them. I'll let y'all know how they turn out.
   - Stormcrow - Monday, 03/28/11 21:22:21 EDT

Mike T.,
In the past, I've got mild eye burn if I've forge welded steadily for one half day to one day, a fairly rare occurence for me. A few eye drops in the evening seemed to help.

I'm not sure whether special glasses are necessary. I've tried didymium glasses, but they only work on sodium flare (the bright yellow of the flame). They make the heats appear as oddly colored.

I see that at least one firm carries glasses that are supposed to handle sodium flare, UV, and IR. sundanceglass.com carries "Green Ace IR" which they claim covers all the bases. I haven't tried them, so I don't know what the heats look like through the glasses.

I hardly wear darkened shades unless I'm electric or gas welding.
   Frank Turley - Monday, 03/28/11 23:19:40 EDT

Mr. Turley,

Thank you for the response.
   Mike T. - Monday, 03/28/11 23:39:19 EDT

One of the largest manufacturers of small (relatively speaking) induction generators, Lepel, went out of business a couple years ago. Actually they ended up being absorbed by their largest customer, a manufacturer of sealing equipment.
   - Grant - Nakedanvil - Monday, 03/28/11 23:44:31 EDT

I often want to use punch marks on work to mark lengths for bending or where to start forging etc.The trouble is when the metal is at a good heat you cant see those marks.Would ace or didymium glasses allow one to see those marks at heat?
   wayne @nb - Tuesday, 03/29/11 08:28:28 EDT

Heat and Safety Glasses Mike, Unless you are doing a lot of welding as Frank noted, OR you are working on very large pieces the infrared from the steel is not a problem. However, staring into a hot forge, particularly a gas forge where every surface is giving off large amounts of infrared can be a problem. Like many things, it depends on your work habits.

Note that both infrared (IR) and UV are damaging to the eyes and the damage is cumulative. However, the amount of IR that is damaging is not clear but it is a known factor in late life vision problems. We researched this and both OSHA and ASTM were so non-specific that they referred to each other for the information (which neither had).

We sell No.2 shade safety glasses for working in the forge. As Frank noted they DO change the appearance of hot iron but I think the color difference is less than with didyium glasses. Blacksmiths Depot sell the didyium glasses.
   - guru - Tuesday, 03/29/11 08:28:58 EDT

Wayne, my post above was made at the same time as yours and was not addressing your question.

Tinted glasses MAY help. Note that the Didydium are designed to filter the orange sodium flare from glass furnaces and also reduce the flare from flux but and not specific to hot steel.

However, reduced vision generally helps nothing. If the work it too bright then shades WILL help. However, when not looking at the hot metal they make is more difficult to see in the shop. That is why we sell the No.2 shades. They give some protection against IR but are not so dark they make it difficult to see otherwise. Ambient lighting makes a big difference in all cases.

IF you have some standard oxy-acetylene welding goggles they SHOULD be a No.3 shade. Try them. Note however that many cutting goggles are No.5's and may be too dark.

Rather than punch marks (which mar the work), you might try narrow fuller marks (a rounded cold chisel). These show up better for me and do not make a hole in the work. While it is probably not a problem I always thought making punch marks where you were going to make a bend was a bad idea.
   - guru - Tuesday, 03/29/11 08:42:58 EDT

In comercial forges, in the days of big gas forges our "heaters" the person the managed the billets into and out of the forge wore shade 4 green lens. Of course these were guys looking into a hot forge every day, and these were big forges.
A.O. Safety has flip up shade 4 glasses that have regular safety glasses as well as the shade lens. They also make a high quality green shade clip on flip up lens. I think I remember that the mill supply price was $29.00 in small quantity.

Remember that Polycarbonate safety glasses will filter UV.
Just another reason to wear safety glasses
   ptree - Tuesday, 03/29/11 10:43:03 EDT

Punch Marks..... Stationary store white out works fine, you can even get it in a fine pencil applicator. Don't worry about it burning off, it's a bitch to get off.
   Carver Jake - Tuesday, 03/29/11 12:54:53 EDT

Punch marks. Scale is awful, but it can be used as a guide. If you mark with a whiteout the length you need on the anvil or scrap material, you can quickly lay your hot picce on it and find an irregular piece of scale to use as a reference when you get to the anvil. You can also use dividers to find the length you need as the work is brought to the anvil.
   Frank Turley - Tuesday, 03/29/11 13:36:12 EDT

punch marks seem to show up better for me when i make a square point punch it seems to stand out better in the scale than a round one now if i could only figger how to temper the punches i make so i don't have to re- sharpen them so often
   danny arnold - Tuesday, 03/29/11 13:50:50 EDT

I made a special cutting plate for my anvil for billet welding: I marked the center of it on a side and then laid out a rule on it from that center in 1/4" increments all done with a chisel---makes it a lot easier for me to see where to nick for the fold.

I often use soapstone on the side of the anvil to mark lengths I need to reproduce and of course the old "bit longer than the width of the face", "Length from the edge to the near/far side of the hardy hole", etc.

Thanks for the leads; I'd like to make this more of a tactical re-deployment than a rout!

Thomas
   Thomas P - Tuesday, 03/29/11 14:08:56 EDT

Vanishing punch marks. If you punch at the outer edge of the metal, the swell it makes will be visible at any heat. You could do on both sides for wide stock.
   Thumper - Tuesday, 03/29/11 15:18:15 EDT

IR glasses: Uvex sells safety glasses that are IR and UV rated. They have a yellow tint, and don't change the colors too much. If you search their catalog online you should be able to track them down.
   Bajajoaquin - Tuesday, 03/29/11 16:22:06 EDT

Guru,
I am about to quote a fairly high end set of andirons (which should be fun to make) but I am concerned about the finish. Is there any paint that will stand up to constant fires? (this is a large fireplace) Is the "traditional" black hot/oil finish and warning to the customer the best approach or do you have some advice?
thanks
Nathan
   nathan - Tuesday, 03/29/11 19:14:12 EDT

Guru, Print: Steel Temper Colors chart the colors do not print. Is there a way?
   - Anver - Tuesday, 03/29/11 19:48:25 EDT

Nathan,

Since this is a high-end set, why not just use stainless steel? The black oxide finish it develops after forging is quite stable. Stainless won't burn up over time, either.
   - Rich - Tuesday, 03/29/11 20:37:35 EDT

Anver, tell your browser printer setup to "print background colors" The default is off.
   - guru - Tuesday, 03/29/11 20:51:46 EDT

Nathan, I'm with Rich on the stainless. But when you use stainless "high end" means REALLY high end. Materials will start off at 4 or 5 times carbon steel and then labor is three times as much. It dulls tools, does not drill or saw well and MUST be forged at a high heat. At a low red it is tougher than stone cold. You will also need various sizes of stock and possibly fasteners.

When heated in the forge and cooled stainless looks just like carbon steel and can be oiled or waxed to darken. But you can polish highlights and generally not worry about them rusting. Just BE SURE to use a stainless wire brush if you clean up with one.

You can't forge weld it but all other processes work. If it needs to LOOK forge welded dress the arc welds in the forge and the results are hard to distinguish.

The cost is high but the results are darn permanent. While they will not resist sagging at high heat any better than carbon steel the supports will not burn out or corrode away if ashes are left around them.
   - guru - Tuesday, 03/29/11 20:59:31 EDT

High temperature paints, such as barbecue black hold up OK but will not withstand temperatures over about 500°F. Fronts of andirons hold up OK due the cooling by the draft but anything in the fire or coals is not going to hold up.

Also note that high temperature paints chalk with age and higher temperatures.
   - guru - Tuesday, 03/29/11 21:03:04 EDT

wayne@nb
I missread your initial inquiry. I thought you were trying to avoid punch marks. A really old method is to punch and at a heat, wipe off the hot scale with a straight edge. The scale will remain and be visible in the punch mark.
   Frank Turley - Tuesday, 03/29/11 21:35:05 EDT

Guru, Did the trick. You Rock!
   - Anver - Tuesday, 03/29/11 23:51:59 EDT

Forgot to tell everyone about my Italy trip. We ended up in a small industrial town outside of Milan called Concorezzo. They couldn't find a small anvil, so I swung a bowling ball as a teaser, then pulled a horse drawn chariot loaded with hot Italian models inside a mild steel welded jail cage. The whole rig (Guinness ajdudicator called it a "vehicle" for record purposes) weighed around 1,000 kilos and was pulled over 20 meters. They fabbed up a railing setup so the carriage wouldn't wander. Problems arose when the load was displacing the air in the tires causing them to rub against the side rails. Their solution was to overinflate the tires and thoroughly grease the rails. I was appalled as a welder to their welding techniques. I attempted to give them advice, but the language barrier made it difficult. I picked up an electrode and demonstrated a weaving technique. They looked puzzled and continued with tacking without eye protection. I also tried to show them to tack the ends of the rails first, then do the supports on the inside at intervals.... nope. They just kept going, saying they would adjust for warping later. I lost count of holes burned through the pipe rails. I'll post pics when I get a chance. Either way, I did acheive a brand new record, got a medal and certificate. It will air on Canale 5 in Italy tomorrow, copyright prevents us from seeing it herein the states, but will be sure to be leaked onto YouTube by next week.
   - Nippulini - Wednesday, 03/30/11 08:54:54 EDT

Nip, Sounds like the welders were some kind of studio crew. . . and the usual "field trip" experiences. Congrats on the new record! The whole thing sounds like the cartoon idea we had of you pulling a circus wagon!
   - guru - Wednesday, 03/30/11 10:10:33 EDT

Yeah, they welded scraps of sheet and perforated all around it, hung chains from the bars with strips of black cloth material. They had this whole "artistic vision" of post apocolyptic slavery or something like that. Yes, very much like your idea Jock.
   - Nippulini - Wednesday, 03/30/11 11:10:21 EDT

thanks very much for your help, guess I should have defined "fairly high end" a little better. Don't think they will go for stainless (but it would be pretty neat).
thanks again
nathan
   nathan - Wednesday, 03/30/11 12:21:00 EDT

Andirons: Nathan, Carbon steel holds up fine. In a fireplace a good even scale finish with DeRusto barbecue black holds up fine.

The only parts that fail in large fireplaces is the log support. These get very hot, often to the heavy scaling or burning point. I've repaired many old andirons that were as big as 1" (25mm) square that had been overheated. It is common for them to get a heavy log dropped on them when at a red heat. So they bend and the andirons tilt back. This then puts the log support down into the coals farther. . . So bigger than 1" does not hurt.

On deep fireplaces it helps to put a support leg about mid span on the log support. Due to levelness problems on masonry floors I make the leg about 1/8 to 3/16" short. If the andiron get overheated and heavily loaded then it will droop to fit where it sits and go no farther.

The support leg on many andirons was tennoned onto the front. This makes them replaceable. On one old set I repaired you could set two or three forge welds in each leg toward the middle where they got the hottest.
   - guru - Wednesday, 03/30/11 12:59:38 EDT

More Andirons: Something I have done on a number of andirons and fireplace tools is make brass accents. There are several methods I've used. I show one method on our iForge page using brass rod and brazing it to the steel parts. Another method is to use brazing rod to put a heavy coating of brass on the steel. This makes a heavy uneven finish but the texture can be interesting. It can be filed smooth or polished as is. The brass over steel is very strong and not effected by heat the way solid brass is.
   - guru - Wednesday, 03/30/11 13:14:21 EDT

Nip, there was a welder in the small Mexican village we were living in that never used a helmet for small jobs.

But he did shield his eyes with his hand. (not OSHA approved)
   Carver Jake - Wednesday, 03/30/11 13:24:05 EDT

You see those photos of Chinese construction welders using a paper bag with slits as a welding helmet and wonder if they are real. . . Of course China is in the stat of expansion we ere in in the 40's and 50's where jobs got done no matter what and WAY before OSHA. The difference being thee are a LOT more Chinese laborers they can use up. And a significant part of the world has become a lot more "enlightened" about safety issues.
   - guru - Wednesday, 03/30/11 16:05:07 EDT

Guru
I'd like to make some windbells (buoy bells)3 triangular pcs of plate in 3 different thicknesses welded together at the upper point. I know in the past you have talked about tubular bells, but I am wondering about the science in the triangle sides. Long and slender (? b x4h) or short and squat( b x 2h).Plate thickness will be 1/4 3/16 1/8. longer sides, more vibration, deeper sound ? Any help would be appreciated
   Yooper - Wednesday, 03/30/11 16:34:38 EDT

Andirons: I have seen ones made from railroad rail that have corroded out in a person's lifetime.

What about making the uprights plain steel and the log supports stainless?

TGN; I'll take your word on your part of the deal please provide pictures of cage and contents to verify the rest!

Thomas
   Thomas P - Wednesday, 03/30/11 17:04:39 EDT

Stainless steel forging.
Having had some experience in the forging of both 300 and 400 series stainless, I can offer the following.
300 series will be easier to find in small quantity. Welds easily in most cases with stick or mig or tig. The scale will rust outdoors. The surface will rust if not passivated and descalled. The surface will rust if worked with carbon steel wire brushes or SS wire brushes if previously used on plain steel. 300 series is usually about 18% chrome and 8% nickel, and is a very corrosion resistant material if properly treated. Forging temp should be a nice lemon yellow, returning to the forge at dull orange.
400SS is harder to weld, and is a high hot strenght steel used usually for corrosion resistance at elevated temps. Also has very good strenght at high temps. All of the rusting rules apply. Forges about the same, maybe a little easier. Most of the 400 series will be hardenable by quench and temper. 400ss machines somewhat easier. Does not tend to gall near as badly and the 300 series. usually about 13% chrome and 4 to 6% nickel.
For a good high temp creep and oxidation resistant steel, that is NOT stainless, and welds ok machines nicely and forges pretty much like plain steel I would choose the steels used in higher temp boilers and piping for the very same reasons. A Chrome Moly steel of about 5% chrome and 2% or less Moly. Roughly equiv to P-22 piping, F-22 in forgeing steel for the valev and fitting trade. This is the steel of choice in 2500 psi/1200F steam. Chossen for that high hot strenght, high oxidation resistance, and good corrosion strenght. Very weldable with stick/MIG/Tig. Needs some preand post weld heat, but still easy.
   ptree - Wednesday, 03/30/11 18:55:22 EDT

We're all idiots! For a high end Andiron job---inconel!

Thomas suffering from extra stress lately...
   Thomas P - Wednesday, 03/30/11 19:33:50 EDT

Triangle Plate Wind Chimes: 40 years ago I bought materials to make about dozen of those. . . the plate is still stacked in my old shop under the bench rusting. I was not happy with the necessary weld joint and how it looked when finished. Most makers just buzzed them together to a round or square hook and that was that.

These don't ring particularly well. Generally low and soft.

There is math for a tuning fork but that is based on two perfectly equal masses moving diametrically opposite. The crux of the math is where the two pieces join and how much of the joint is bar and how much is not. While the math for the length LOOKS straight forward I had to do a lot of tweeking of the text book math to get accurate results based on measuring actual calibrated tuning forks. . but that is another story.

In the three sided wind chime each plate is vibrating in balance to the opposite two at an angle toward the center of their mass. Due to unequal masses this is not where you would think it is. Then those plates are vibrating toward opposite centers of gravity. . . As they move so does the theoretical opposite. It would make a good math thesis to figure it out (and prove it).

Anyway, back to tuning fork model. On the triangles which constantly vary in width the location of the end of the joint determines the stiffness of the plate attachments. The nearer the point the more flexible (and lower the pitch) and the farther down the triangle the stiffer and thus shorter motion (higher pitch).

   - guru - Wednesday, 03/30/11 19:35:13 EDT

ThomasP, ever forged or machined Inconel? I have,when forgable, as well as titanium, Monel,Hastaloy A and B, Waspalloy,Nimonic, TitaniumZirconium, F-22,F11, P-8 F-6 and several I am not allowed to discuss.
All of are a royal pain to forge, if at all forgable and most machine only in extremely rigid, powerful machines, and in the case of several of these top of the line taps last exactly one hole.
By all means for a high end job go Inconel:) May I suggest the Inconel X625? One of the worst machineing alloys I ever worked with.
But the titaniumZirconium would also be very high end as only one US supplier exists, Teledyne Wa Chung out west, and you need a government license to buy it:) Last project I did used 7" cubes, and in about 1992 they cost almost $10,000 USD each.
   ptree - Wednesday, 03/30/11 20:34:39 EDT

We stamped a small part from Inconel, a spring for Central Automatic Fire Sprinklers. These springs had to be able to shut the sprinkler off after the fire was extinguished. They were pure hell on the tooling.
   - Dave Boyer - Wednesday, 03/30/11 22:33:29 EDT

Tantalum andirons.. the rare earth solution

I learned about tantalum from an interesting article in the last ASM International newsletter about a tantalum treatment applied over steel. in the article it's used in elevated temperature acidic environments and is replacing super alloys consisting of mostly nickel. in comparison the initial cost is close to the same, but the tantalum serves a much longer life.
   - Ty Murch - Wednesday, 03/30/11 22:36:20 EDT

Andirons. I'm sure unobtanium would work fine and is easy to forge and never rusts. It's a little difficult to obtain though.
   Carver Jake - Wednesday, 03/30/11 23:13:50 EDT

I have a two burner blacksmith forge from diamond back. I notice that when I heat stock lets say half inch I cannot get it a bright yellow. The stock gets bright red but I cant seem to match that yellow heat I see on all the you tube videos. Is this because I am using a gas forge and not a coal forge? does it matter?
   Mario - Thursday, 03/31/11 00:49:38 EDT

Mario: Properly insulated gas forges with large enough burners for the forge interior size will get to welding heat or higher.

Not being familliar with Your forge, I can't say if this is normal or not. Can You increase the operating pressure to get more heat? If there is a lot of open area, reducing it some, but not enough to interfere with the burner operation will help.
   - Dave Boyer - Thursday, 03/31/11 01:54:54 EDT

Mario, Generally you crank up the gas pressure to get the forge hotter. Note that the suggested pressures for these things are low enough that common pressure gauges do not read very accurately. A gauge reading 4 PSI many be reading an actual 2 to 10 PSI. You can also have obstructions in the line reducing the pressure at the burner. Often the forge opening is too large and needs to be partially blocked to raise the temperature.

If in doubt ask the manufacturer.
   - guru - Thursday, 03/31/11 03:04:58 EDT

Mario,

are you using a picnic bottle with the new valve? Some of the ea4ly iterations of those OPD valves won't allow full flow - unless you open them extremely slowly, and sometimes not even then. A Diamondback forge should easily get to a high yellow heat.
   - Rich - Thursday, 03/31/11 09:46:47 EDT

Inconel: It was a *joke*! We made sword fittings out od some once; quite pretty and a pain to work!

Video's also think about how the camera interpreted the temps; I've seen pictures where the photo is way off what the eye saw.

Thomas
   Thomas P - Thursday, 03/31/11 12:00:08 EDT

NIP, If you haven't seen it, check out the movie "Fur".
   Carver Jake - Thursday, 03/31/11 12:40:49 EDT

ThomasP, I knew:)
   ptree - Thursday, 03/31/11 14:42:06 EDT

Mario,
This is Dennis from Diamondback Ironworks. What forge model are you using and what pressure are you running?
   - nordic_rage - Thursday, 03/31/11 18:49:54 EDT

Hello, I have a small Champion rivet forge: 3 legged stampe steel hearth with blower bolted directly to the hearth. Works fine. I just saw a similar forge for sale at $50. That forge has a 4 legs cast iron hearth and the same blower as mine. Question: are there any advantages with a cast iron hearth? I did not find anything about that in FAQ or IFORGE. Thank you!
   donald - Thursday, 03/31/11 21:04:54 EDT

Donald,

A cast iron fire pot is less likely to burn out or rust away from the acids created by coal ash. At least I'm assuming that when you use the term "hearth" you really mean the fire pot. If you're referring to the flat area surrounding the fire pot (what I would call the hearth) then cast iron is not only less likely to rust out but the increased mass also means better stability when heavier work is in the fire.
   - Rich - Thursday, 03/31/11 22:25:34 EDT

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