Blacksmithing and Metalworking Q&A : anvilfire Guru page : Dec 16

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This is an archive of posts from December 16 - 21, 2007 on the Guru's Den

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I have research a little bit about crucibles for melting steel and was wondering if you all could share some of what you know with me. First of all, does anyone know of a cheap way to make them? What about alumina, how hard is it to mold and treat? Any good resources on this stuff? I have found alot of opinions but very little information. Please point me in the right direction.
Thank you all
chem geek

- chem geek - Saturday, 12/15/07 21:17:47 EST

In the propane forge I use on a day-to-day basis I only started to experience back flash after I put in a second layer of insulation. Blue in flame increased noticeable and if I cut back on pressure too much it pops and back flashes. I suspect I reduced the chamber size too much for the size of air tubes and gas orifices.

Ken Scharabok (Poor Boy Blacksmith Tools) - Sunday, 12/16/07 05:49:41 EST

Thanks guys, I will try both Increasing my pressure as a 1st step and the Ken and Guru are basically saying the same thing. If my burner are not matching the chamber I might have a problem. I will test both and in the mean time thanks a million for your input.

Dan

Dan - Sunday, 12/16/07 08:33:11 EST

Chem geek,
Do you have to have a crucible? Why not use a cupola?

- philip in china - Sunday, 12/16/07 08:38:23 EST

Mike: Burn back is the result of a balance between heat transfer to the burner nozzle and the speed of the mixture flowing through the nozzle. When the mixture ignites in the tube, the gas is not flowing fast enough and has time to reach ignition point. With a blower, you can simply reduce the size of the burner tube but atmospheric burners are more fiddly. As Ken says, more insulation can produce this effect. And of course, turning the burner down to low invites this effect. So too can constricting the air flow by blocking the mouth of the forge too tight. The trick to keeping the forge hot is not necessarily blocking gas flow but reducing radiant heat loss. You can block the mouth of the forge so that the gas is free to flow but there is minimal line of sight for light to leave the chamber and most of the heat gets reflected back. I would consider placing the nozzle so that it is almost completely outside the wall of the forge and making an extension of kaowool and ITC100 to guide the mix the last inch or so into the chamber. A fancier option is to get a burner tube with a taper running the whole length. In such a burner the mixture velocity increases as the tube gets narrower and the burnback will find some balance point and stop before reaching the neck of the tube.

adam - Sunday, 12/16/07 09:28:24 EST

Crucibles: Chem Geek, You are much better off and much safer purchasing commercial crucibles. Their manufacture and obtaining the high quality materials to make them has been a technical specialty left to others for thousands of years.

High temperature refractory chemistry is a specialty that few understand and is often learned only in the industry.

If you google high alumina clay you will find articles to its uses and sources. Example see:

http://www.springerlink.com/content/j4k72591558v2864/

High temperature refractories require special high temperature binders AND must be fired at exceptionally high temperatures.

For most high temperature work today graphite and silicon carbide crucibles are used. These also require a high temperature binder Example see:

www.aremco.com/PDFs/A11_06.pdf

While this document is selling a proprietary product is does list a long list of refractory substances it is compatible with.

See also:

www.blackwell-synergy.com/doi/pdf/10.1111/j.1151-2916.1919.tb17529.x

This document cannot be accessed without paying a few but the fee gives you access to many other similar articles.

Once you learn what you want then you will find obtaining the materials to be a significant challenge. This is an industry that only deals with more industry and freight car loads are the normal amounts bought and sold. Occasionally you can find 55 gallon drum sized containers of refractories. This does not sould too bad until you realize that that is 500 to 800 pounds of material you will need to handle. I have a nice little 3,000 pound Caterpillar fork lift I can give you a deal on. . .

Consider one of the most common refractories used as fill in refractory cements and bricks, synthetic mullite. The material is mined in huge open pit mines such as the one in central Virginia. The material is ground in huge rock crushers and made into a powder. It is then made into a paste that is extruded into bars which are then fired in a high temperature furnace. This is then ground up again graded in various sizes and then loaded into RR-cars and those 500 pound dry material drums. This is then sold to other big industry. There are no small dealers in this loop. . . You are lucky if they will sell a sample drum for R&D. I know, I tried.

- guru - Sunday, 12/16/07 11:38:54 EST

Chem Geek, this reads to me like "since parachutes are so expensive I want to make my own and go skydiving with it"

Unless you already *know* how to work with crucibles I would not suggest working with a homebuilt one. I'm reading "Steelmaking Before Bessemer, vol II Crucible Steel" right now and reading about how crucible failures were common and they were doing it as a commercial process. (they describe a bit on how they are made too).

Safety is CHEAP, SAFETY IS REAL CHEAP!

Phillip; Cupolas are for cast iron and do not work well for casting steel as they tend to convert it to cast iron and add sulfur to it.

Burn Back: in my aspirated forge I start to get burn back if the nozzle is not in perfect alignment in the burner tube.

Thomas

Thomas P - Sunday, 12/16/07 11:40:05 EST

The guys melting aluminum make a lot of their own crucibles, particularly for tilting furnace arrangements where the entire furnace tilts to pour the crucible. See the reviews of the books by Chastain on our book review page.

There are a couple methods used. One is a bare steel pipe crucible. These last a very short time as the aluminum dissolves the steel and soon you have hot aluminum pissing on you (a distinct safety problem). Besides wrecking crucibles every 5 or 6 pours that iron went into the melt which is bad for the aluminum.

The second method is to use the same crucible with a ceramic lining. This stops or slows the problem of dissolving the steel. But it is not cheap to do. I asked the manufacturer of ITC-100 about this. He got a little upset that people would be so cheap as to want to do this. The ITC products to do it are expensive and there is not a lot of cost savings. Why not purchase a commercial crucible? . . . Anyway, starting with clean steel you apply ITC-213 and then ITC-296-A. Then between every pour you need to inspect the crucible and repair damage to the thin lining.

The best method since it is required for a tilting furnace is to start with the steel shell and line it with an inch or so of castable refractory. I THINK that is the method Chastain uses (I'm away from my library again). To reduce sticking of metal and dross commercial foundries use ITC-100 over the castable to helps smooth and fill the surface and then ITC-296-A over that. Dross buildup can clog a crucible to whee it is almost useless.

Note however, that some crucible makers make special crucibles for use in tilting furnaces.

Melting lead, zinc and aluminum you can get away with using iron or steel crucibles. Note I said "get away", it is not the best way. For higher temperature metals such as copper alloys you want commercially made high quality crucibles and even THEY occasionally fail. Besides the crucible you also need professionally fitted lifting tools.

Spilled metal is one of the biggest causes of injuries and deaths in the foundry business. In 1838 James Nasmyth invented the mechanically operated safety ladle. He thought this was so important an invention and that it would save many lives and prevent injuries that he gave away the invention as a service to the foundry industry.

While you can see from his illustrations that there would be some nervousness and anxiety when pouring from such a large ladle the same is true in the small foundry with a one man operation as well. Handling hot liquid metal is a little scary and this can lead to nervousness and that to accidents. It pays to use the best equipment.

- guru - Sunday, 12/16/07 14:46:14 EST

Keith,
To straighten twistied bar w/out marring, use a weighed (replaceable faced), raw hide mallet on a wooden stump. It works either hot or cold. For big twists make a depression in the stump and work over that.

Roland - Sunday, 12/16/07 14:50:24 EST

Keith, I am fond of a wooden mallet, grown by nature. I found a nice little sapling with a near horizontal branch of about the right diameter, and 30 seconds with a chain saw and I have a wooden mallet to softly persuade steel over my pine stump. I did put ring of steel around the head ends to stop splitting.

ptree - Sunday, 12/16/07 16:58:18 EST

A friend of mine straightens twists in his vise. He just squeezes them so the jaws force the high spots down. The pressure from the jaws is even enough that it doesn't mar the bar to speak of. I guess you could use aluminum jaws if you were obsessive.

Mike BR - Sunday, 12/16/07 21:21:02 EST

To straighten a slightly skewed twist, just whack the bar on an area that isn't twisted and let inertia do the work. Try it, and you'll see how this is far easier than a mallet and can be done on the same heat as the twisting. It takes a bit of practice to learn where to apply the force to get the desired result, but you'll soon have it down pat to wher it is done almost without thought.

vicopper - Sunday, 12/16/07 21:37:20 EST

Crucibles:

I've done a fair amount of small castings (up to about 250#), and I am trained to do both jewelry and sculpture casting by several methods. I would NEVER, under any circumstances, for any amount of money or other inducements, attempt to make my own crucible for melting steel. Not even for bronze, silver, gold or aluminum. I know what damage molten metal does to the human anatomy and how fast it can happen, even when you are using the very best equipment made. Even a silicon carbide crucible is cheap, compared to just one visit to the emergency room and the follow-ups with the plastic surgeon, rehab center or worse, the mortician. To use some home made container for molten metal at a temperature in excess of a thousand degrees is just plain foolhardy.

vicopper - Sunday, 12/16/07 21:53:34 EST

Vicopper,
Slick idea, how large a diameter rod will this work on (1.25in hex is the largest I've done to date, wish I'd have known about that method then)?

Roland - Sunday, 12/16/07 22:07:54 EST

I suppose it would work on any size, you just scale up the forces.

vicopper - Monday, 12/17/07 00:16:15 EST

The inertia method of straightening bar works as well on large bar as on small. The larger the bar the more the inertia. It does not take much different a tap with a 1" bar as with a 1/2" bar. In fact, if the large bar is very long the added weight on the ends greatly increase the force. You just have to practice a little on whatever size you are working. A combination of letting the bar do the work and a wood mallet and sharp cornered twiasts can be straightened without damage. However, the best thing to do is to pay attention when making the twist and keep it straight in the process.

- guru - Monday, 12/17/07 01:57:28 EST

Band Saws and other ways of making long cuts:
I am wondering if one could use an old tablesaw (I have 2 that were "gifts" from friends moving away. Could one put the blades off chop saws on them after they wear down to about 10", then use taper jigs, fences etc to make long angle cuts on flat bar, etc? Or is this just way too iffy?
Thanks for all your info, the site is a goldmind.

- Tim in Orygun - Monday, 12/17/07 11:24:48 EST

Table saw with abrasive blade. Firstly this is not recommended. Secondly I do it all the time. It works fairly well though its slow and you have to watch for the cut warping and binding on the blade. I never use a guide, I just feed by hand and follow a line drawn with whiteout or chalk. You are not going to get the kind of precise cuts that you can get when cutting wood and there is quite a lot of burr to clean up. The abrasive grit is very unkind to the table saw and I would not do this on a machine that I wanted to keep in good shape. OTH I have been using a really cheap TS of Harbor freight quality to do this and it has held up for years.

adam - Monday, 12/17/07 12:11:27 EST

There are two problems using a table saw with an abrassive wheel. 1) If it has been used with wood it needs to be cleaned very well. Wood powder gets everywhere including in motors and is very flammable. 2) Some saws and motors have good seals that cen take grit and others do not. There is no way to tell. However, if there are slightly open bearings then the saw will have a very short life and this is a possibility you should be aware of.

- guru - Monday, 12/17/07 12:46:18 EST

The learning curve for casting often starts with relatively low temp metals like pewter, tin, lead and then steps up to Al and then jumps up to brass/bronze and then steps further up to silver, copper, etc. Things like steel are another hefty step up still (and I won't mention Platinum...)

Each step higher in heat requires changes in equipment and safety practices.

"Steelmaking before Bessemer, Vol II Crucible Steel" has been a fascinating read as they discuss making crucibles and crucible failures. It mentions a crucible as being soft at heat and great care needing to be taken lifting and manuvering it as to not squish it with the tongs. It mentions rather common failures and trying to save the molten steel from a degraded or failed crucible and mentiones that many a teemer has had a sip of molten steel in his clog.

I study 19th century methods when I want to try to recreate a process and can't afford to go high tech---a nice modern crucible in a vacuum chamber with an induction heater solves *SO* many possible issues...But the more I read up on the safety issues and problems they had getting a clean melt, the more it seems like using known good "modern" technologies is indicated.

I do try to recreate medieval technologies as part of experimental archeology; but I expect a lot of failures and use modern safety gear when doing so. I confess to being tempted by Dr Feuerbach's thesis on "Crucible Steel in Central Asia"; but will probably try it with modern crucibles *first*!

Thomas

Thomas P - Monday, 12/17/07 13:14:41 EST

Thinking about getting a machine part from a rock crusher to use as an outdoor forge. 42" wide at the top then narrows like 1/2 a bell. 2" thick sides of solid metal with carbon, manganese and chroium alloys. Not cast iron, toss it off a truck and it rings like a bell. Weighs about 600 pounds. Bottom has a 12" opening and there are four attached links that function as legs when using as a forge.
These are links 10" long.I was thinking of blowing air with a bellow and piped from underneath air. Don't know what to use as a grid to keep the coal/old burned wood material from falling out. There is a 2" gap if sitting on a solid structure but I guess if I put it on dirt the weight will sink it to the hole anyway.
Question: I have an opportunity to return it as the weight is extreme and moving it will be a problem. I am also wondering if the alloys might pose any danger since this wasn't meant to use as a forge.I have pics I can send...adice would be greatly appreciated. BTW the thing cost me $300.

Dean Lapinel - Monday, 12/17/07 13:38:11 EST

Dean, Folks near us have a depot that supplies these parts all over the country and I have had a look at a number of them.

I would not use them as a forge for the following reasons.

1) The center hole is too large. You can just about put a full size fire pot into it. Full size (large shop) forges have about a 3" intake with air forced through about a 2" opening.

2) The part is much too heavy and will make a top heavy forge that is also a big heat sink and will stay hot long after the fire is out.

3) You can buy all of the parts (fire pot, blower, gate) for a forge PLUS some steel for the rest for what you paid for this odd piece of scrap.

The alloys in the steel have no bearing on the use as a forge. Everything from dirt to brick to cast iron to armour plate has been used for forges.

- guru - Monday, 12/17/07 13:49:55 EST

Thomas,

I bought Vince Gingery's book on homemade crucibles specifically for that reason. I wouldn't actually use one with a molten charge that I intended to handle. But my understanding is that the wootz process described by Feuerbach has the crucibles placed in the furnace cold, then left there after the melt to slowly cool -- no handling required, except at ambient temperature. In that case, isn't even the worst-case scenario for a crucible failure pretty harmless? Of course it'll screw up the charge, but isn't that about the worst of it (assuming you don't fall through the roof of the furnace)?

Matt B - Monday, 12/17/07 14:24:35 EST

Special case Matt, you didn't mention that with the original post! Yes it would be a lot safer working them that way; though failure messes up the furnace a bit; Of course the chemistry of the crucible and the flux makes a big difference in how well a melt goes and crucible longevity.

In the Huntsman Process the Si in the crucible actually helped to degass the charge and so the high heat "soak" that allowed the Si to get into the charge was necessary. Modern "killing" methods work a lot better though (Al pill for example)

I would still think about learning the process with standard materials though---easier to figure out what's going wrong/right if you are familiar with how it's supposed to work.

Does the Gingery book deal with such high temp requirements for the crucibles? Before taking up smithing I had never melted a flowerpot or cinderblock or found out how friable firebricks become after use. Now I'm more aware of how "hot short" much of out common materials are.

Thomas

Thomas P - Monday, 12/17/07 16:18:43 EST

Thomas,

Just to be clear, I'm not sure what chem geek wants to do with his crucibles, and in the absence of further info I think your advice to him was spot-on. I just chimed in with my own idea since it seemed to fit the conversation.

Gingery mentions aluminum and I believe bronze; I don't think he mentions CI. I'll check when I get home tonight. He *certainly* doesn't mention steel. But with pure kaolin and a kaolin grog, and no flux in the mix, the slump point should be over 3000 F -- so it *might* work if all it has to do is hold together for a single melt.

I'm not too worried about messing up the furnace, since I envision it as not much more than a hole in the ground (very similar to the Merv furnaces pictured on Feuerbach's website).

Matt B - Monday, 12/17/07 17:14:39 EST

I am making an air gate from a piece of 1.25" black pipe. The gate will be circular, of course, and swivel on a 1/4" bolt. Whats the best way to drill thru the center of the bolt at rt angles to the long axis so that I can tap it for a #8 machine screw? Thanks

adam - Monday, 12/17/07 18:12:52 EST

Adam-- make a V-block out of some angle iron welded to a piece of plate (plate goes into your drill press cross-vise. What? No cross-vise? Get one forthwith!) to hold the bolt snugly and then clamp the bolt into the angle with a Visegrip. Centerpunch bolt and Bob's your uncle.

Miles Undercut - Monday, 12/17/07 20:13:06 EST

Adam, The "best" way is in a small milling machine since the spindle is very rigid and the vise as well. I like to spot the place to be drilled with a small end mill before drilling. The second best way is in a drill press using a work holding fixture in a solid vise (I dislike so called "drill press" vises with the tilting body because they are not very sturdy). It helps again to spot the angular surface with a small end mill.

Next to last, a small hand drill and steady hands. I like low speed drills for controlability. Very last but still possible, an old fashioned pump drill with reversable bit.

The key to all drilling is proper feed pressure so that the drill does not rub and work harden the material and dull the bit. Next is angular control. Some people can hand hold drills square or at the proper angle and other cannot recogniize sqaure +/- 20 degrees. . . Good machines provide both.

- guru - Monday, 12/17/07 20:18:03 EST

Tim in Orygun-- Lindsay (www.lindsaybks.com) sels or used to, anyway, plans for a frame that holds an oxy-acetylene torch for making long, precise cuts. While awaiting the perfect day to make it, last few years since getting said plans, I just use another piece of steel as a straightedge.

Miles Undercut - Monday, 12/17/07 20:21:27 EST

Argh I feel like clubbing my self on the head right now. For any one who lives near toronto, you know that we just finished digging out of a big storm and I took this opportunity to do the heat treating on my file knife before more white stuff arrives. Well after my heattreating in the freezing cold outside, I stuck it in the oven WITHOUT checking the temp colour chart first and set it to 350 deg C. Well it was only for a few minutes, but the blade had already formed the gray oxide on the surface. I have dropped the temperature now to 250 for the rest of the tempering, but is my heat treated edge already doomed to be sub 60 on the rockwell scale? Keep in mind, this is a very thin blade already, if I grind anymore surface material away, there will be nothing left. Oh and will it also have any effect on the hamon that 'may' have been present?

Nabiul Haque - Monday, 12/17/07 20:48:51 EST

Nabiul: Once the work gets too hot in the tempering there is no going back. You will have to harden again, then temper properly. For 60+ rockwell many steels will hardly show any color. I don't remember from Your earlier posts what material You are using.

- Dave Boyer - Monday, 12/17/07 21:20:49 EST

Brrrr!-- anybody know about anything user-proven wonderful in insulated leathern boots (not Sorels, they are indeed wonderful but are rubber bottomed and will melt) that will keep my tootsies warm whilst (love them Brit words, love 'em!) welding, smiting, outdoors in c. zero F. weather but won't cause the dread foot-sweat chill? I've tried two layers of woollen socks and Ensolite insoles inside my Red Wings. Lasted a few miserable hours but had to stop for fear of frostbite and gangrene. Steel toes and built-in metatarsal guards would be nice, too. Any such around? Many thanks!

Miles Undercut - Monday, 12/17/07 21:24:21 EST

I am using a ruined file as my material. I want it hard enough to hold a good thin edge, but not so hard that it cracks from me slightly putting pressure on it, which happened with my last one.

Nabiul Haque - Monday, 12/17/07 21:34:33 EST

Yay for learning surprise #2, apparently 1 and a half hours in the oven was not enough, for most of the knife the tempering only affected the surface layer. When I tried to bend the knife back into shape from the slight side curvature it took after heat treating, it snapped in half but there was a lot more 'flexibility' in it than the first one. Interesting to note, this one was clayed and quenched in warm water, the inside crystal structure is very rough and large grained where as the old one was very fine grained. There is also a transition in this one from being fine grained on the outside to the large crystals inside that I can clearly see in it's cross section.

Nabiul Haque - Monday, 12/17/07 21:46:51 EST

Nabiul, Rockwell C 60 doesn't mean all that much on a knife. It's just a conical diamont point penetrating the metal under a 150 kg load, and there's a digital readout. Bully bully! Besides hardness, what matters is flex and spring-back, edge holding ability, and toughness. If your Rc is in the area of 55 plus, you should be OK. Coarse grain may mean that you hardened at too high a heat. The warp usually comes during the quench. I would recommend using oil on thin blades such as yours (the file steel). If the blade warps in the quenchant, it's best to heat to a red, straighten, normalize, and harden again. It is also good to leave the cutting edges blunt before hardening, which helps a little in preventing warpage. Don't sharpen and then harden. If you do, the edge is going to scale away, anyway.

Frank Turley - Monday, 12/17/07 22:04:12 EST

Well I may be using the term grain in appropriately in this case, and I didn't sharpen the edge before hardening I left it at about half a millimetre. I think what happened is that one side having a more apparent bevel on it caused the bending. This picture should show the steel structure.

http://img403.imageshack.us/img403/6460/grainib9.jpg

http://img403.imageshack.us/img403/8497/snapuh7.jpg

As you can see the 'tempered' one didnt break cleanly, for my next one I'll be sure to grind away the teeth before forging so that they don't give the knife a greater chance to break.

Maybe the blacksmith gods are just cursing me for ruining good nicholson files.

Nabiul Haque - Monday, 12/17/07 22:24:54 EST

i had a fella once tell me that engine valves were too hard to do anything with (60 Rockwell). Some folks have no idea what happens to inconel at 1800-2000�. I also guess that they ( engineer ) knew nothing of process to make the valves. I was also told the same about Thompson rod ( injector knockout rods for plastic processing ). This has nothing to do with the posts about the knives but I guess it was on my mind.

- Ten Hammers - Tuesday, 12/18/07 06:46:50 EST

Back on twists, I sell pokers with a twist in the middle of the shaft. At first I took out the plug in the back of the propane forge and heated the entire middle area. Don't remember how I figured it out, but I now put just the area to be twisted in front of the forge front opening. Just the right size opening for my twist area. If I was doing production work I could put on clips to hold about three pokers at a time.

Ken Scharabok - Tuesday, 12/18/07 07:54:17 EST

File knife

Here's some shots of a file knife I made for my brother in law. He likes to fish (and who here doesn't?), so I made it into a filet knife, I plan on calling it the File-T knife, get it? Anyway, I forged it into shape, annealed it, used various grinders to shape further, hardened, tempered (by hand with a torch), sharpened, then polished. Does hammering at low heats really pack crystals? This is how I do knives, your mileage may vary (I've always wanted to say that here).

http://greatnippulini.com/fileknifef.jpg

http://greatnippulini.com/fileknifeb.jpg

- Nippulini - Tuesday, 12/18/07 09:00:05 EST

Oops! I forgot to add, this knife is made from a cheapo dollar store variety file. I hold on to my Nicholsons for bench work, keeps the smithing gods on my side.

- Nippulini - Tuesday, 12/18/07 09:03:11 EST

A detail of edge and point shot

http://greatnippulini.com/fileknifedetail.jpg

- Nippulini - Tuesday, 12/18/07 09:10:41 EST

I didn't think you could find files in dollar stores, thought it wasn't something that could produced cheaply any ways, I'll have to start looking now, but then again you can never be sure of the quality of the material.

That is a very nice knife, but it was worked on a dry anvil wasn't it?

Nabiul Haque - Tuesday, 12/18/07 09:44:01 EST

old worn-out files are a dime a dozen at flea markets, yard sales. Even If the files have been left lying transverse to a lee line, chances are excellent they still have more than adequate forgeability.

Miles Undercut - Tuesday, 12/18/07 11:25:02 EST

Nabiul, the cheap files are high carbon enough to be used as-is, but are poorly made. This one was a half rasp/half file doohickey, I prepped it by sanding/grinding all the burrs from the rasp side. Miles is right about old files as well, pretty cheap and usually reliable tools. I prefer to buy old punches @ $1.00 ea at flea mkts and then forge them into shaped punches. I am not familiar with the phrase 'dry anvil'. I do all my heavy "squishing" work on my 200 lb. PW and the finishing/lighter work on a 100 lb. Wilkinson anvil mounted slightly higher.

- Nippulini - Tuesday, 12/18/07 12:04:07 EST

Nip,

Nabiul is referring to the pitting on the blade. Keeping the anvil and hammer wet helps keep the surface of the blade smoother and less pitted; the water blows the scale off the blade (little tiny steam explosions) before it gets a chance to get forged into the steel. Japanese trick.

Matt B - Tuesday, 12/18/07 12:32:01 EST

See, I actually LIKE that effect as well as leaving marks of the hammer blows... I feel like it shows that it was made by a peson, not a machine.

- Nippulini - Tuesday, 12/18/07 12:42:08 EST

I like the look on other people's blades, in some cases; Tim Lively's, for example (although Tim has decided to move away from hammer finishes). I find it hard to bring myself to leave it on my own. It gives me the urge to draw-file. Weird, eh?

Matt B - Tuesday, 12/18/07 13:35:55 EST

Nabiul,

Hard to say what's going on with that blade of yours without a detailed run-down on your heat treating procedures, but here are a few relevant questions.

1) Did you do anything after forging to prepare the blade for hardening? Anything to make the grain size smaller and more uniform?

2) What temperature did you austenitize at, and for how long?

3) What was the temperature of your blade when you started tempering it?

Hard to know the right answers to any of those questions without knowing exactly what steel you're using, but we can probably make some educated guesses.

Matt B - Tuesday, 12/18/07 15:03:04 EST

mr guru i come to u with most respect to your vast metalworking knowledge with the hope that u can help me! i have a question concerning a small gas forge. its made from a 3lb coffee can and lined with koawool 1" liner and a mapp gas torch 2/3 of the way back inserted in a 1" nipple in the top 1/4 of the way down the side. my question is it dosent seem to get hot enough it will heat a piece of steel approximatly 1.5 inches long red hot but no further. to make it heat a longer amt. do i need to repposition my torch? i have it shooting straight acrossthe top so it hits the liner so it will help make it swirl.should it have been at an angle? do i need 2 torches? the pictures ive seen on other sites show similar sizes with the same torch for a heat source. any advice you could give would be a great help!!!!! thanks

bill - Tuesday, 12/18/07 17:57:57 EST

bill - Tuesday, 12/18/07 17:58:13 EST

I do not do anything special or any normalization what so ever, I don't have the time nor fuel to do such things at the present. What do you mean by austenitize, annealing?
The temperature of the blade was a little colder than room temperature when I started tempering. I think the main culprit here is the water being too cold from sitting outside. The high carbon content of the files must be hardening too much. Also the 'clay' coating gets blown off when I quench it.

As for having a handmade look, it's nice for certain types of blades, but the japanese type I am aiming for are going to be differentially tempered, and they look much better with a glass like surface.

Nabiul Haque - Tuesday, 12/18/07 18:18:30 EST

Bill, most of the can forges I know of have very small inner diameters. I would think a 3# can with only 1" of kaowool would be too big an area to heat. Have you tried adding another layer of kaowool to reduce the size?

Nabiul; may I comment that you seem to be wanting to do quite advanced processes without knowing the basics first. This usually results in a lot of frustrating failures.

May I suggest you read up on heat treating blades so you do know what annealing, normalizing and austenitizing are and why they may bee needed even if you do not have time or fuel---it seems like having a blade that breaks and has to be replaced would eat up more time or fuel than getting it right the first time.

"The Complete Bladesmith" by James Hrisoulas would be a good start; though most bladesmith oriented web sites will have information on heat treatment of blades.

Thomas

Thomas P - Tuesday, 12/18/07 19:59:34 EST

Ok I checked what austenitizing was. I don't know what temperature it was exactly since I don't have the equipment, but the blade was a orange yellow colour. I didn't do the magnet test, maybe I should start doing that.

Nabiul Haque - Tuesday, 12/18/07 20:17:06 EST

With a little practice, and knowing what to look for, one can tell when steel is austenized by its appearance.

In the heat treatment of steel, microstructural transformations are yielded by time and temperature. It takes a certain temperature, and a certain amount of time for a steel to become austenitic.

What you are looking for is the disappearance of any shadowy-ness on the surface of the steel. The light on the hot steel will be complete, no shadowy-ness.

Remember, it takes temperature, AND time to austenize steel. You may not need to raise the heat, but only to wait a few moments longer.

TM - Tuesday, 12/18/07 20:33:11 EST

A difficult feat to accomplish when the blade is 90% covered with clay. :)

Nabiul Haque - Tuesday, 12/18/07 21:35:28 EST

Miles- Having worked outside most of the last 15 winters in Vermont where we often see -0F and occasionally -40 both scales, I have some advice.

1: Granma always said "If your toes are cold put on a hat."

2: You may be a heavy persperation body type (like me). No amount of insulation will work if it is filled with water. You may be TOO warm and sweating into your boots. Try a thin wool sock (cotton kills) and put on your boots just before going outside. Make sure your boots are dry from the day before by storing overnight by the woodstove or on a heating vent.

3: Have a scrap piece of plate that you can heat up and stand on (modest heat) or throw onto your NON-COMBUSTIBLE floor and warm that up. Watch out for concrete spalling. Same technique also works for turning the anvil back into an anvil rather than just a heat sink.

4: The best saftey is between the ears. Be extra careful and ditch the steel toes- they really are much colder. If it's REALLY cold reconsider Sorrells for the same reason. I always thought that by the time they heat up enough to ignite I might have noticed and jumped into the snow. BTW if you find spark/scale/slag proof shoe laces please let me know.

5: It may be warmer by noon. Have another cup of coffee. Call to check in with the clients. Surf ebay. Order stock. Order coal. Wow, 3:00 already?

Jud Yaggy - Tuesday, 12/18/07 22:11:03 EST

Nabiul,

It's good that the blade was at room temperature when you put it in the tempering oven. It should be.

Orange yellow is probably too hot. Hard to say since judging temperature by color is so imprecise -- and we don't know what steel you're dealing with -- but that'd be my guess. Overheating could account for the large grain size and brittleness, although I suspect you have other problems as well.

By the time you've finished forging your grain structure is liable to be a mess. It seems to be pretty much universal among professional bladesmiths to invest some time getting the grain back to a uniform, relatively small size. This isn't hard, and takes very little time and fuel compared to forging a blade. A common approach is to normalize the blade several times at successively lower temperatures -- say, A3/Acm (full austenite)+100 degrees , then perhaps A3/Acm+50, then just A3/Acm. (A lot of arguments get started on bladesmithing boards re: this subject, so I'll just add that there are other approaches.) If you don't know what "normalize," "A3" and "Acm" mean, these are terms you should learn. Here's a good reference: http://www.feine-klingen.de/PDFs/verhoeven.pdf

The magnet is helpful if you don't have anything else. It's not perfect, but it's better than nothing. Note that you need to use the magnet as the temperature is rising; when the temperature of the steel is falling, it'll become magnetic again at a very different temperature than the one at which it became non-magnetic on the way up.

As TM said, it is possible to see the allotropic transformation to austenite, which has been described as a faint shadow rippling across the surface of the blade. But you need the right lighting, and even then it's subtle and easy to miss. A combination of the magnet and watching for the "shadow to run" will probably help get you in the ballpark. If you're quenching with a clay coat it's not important to see the shadow on the entire blade. You're only trying to harden the uncoated part of the blade, so that's the only part that really needs transform to austenite.

Matt B - Tuesday, 12/18/07 23:31:32 EST

Jud-- thanks. I've seen the movie. What I am looking for is a specific brand that somebody has experience with outdoors in the snow for hours and hours that works, is all.

Miles Undercut - Wednesday, 12/19/07 00:12:36 EST

;)

TM - Wednesday, 12/19/07 06:50:12 EST

Jud,for heat/spark proof laces, I buy leather ones, works very well for me

- ravenscraft - Wednesday, 12/19/07 07:26:34 EST

Ok thanks I will try that with my next blade over the holidays. Expect another broken blade most likely within a week ;).

Nabiul Haque - Wednesday, 12/19/07 07:38:53 EST

for anyone that might be interested, I just discovered in the new Acklands Grainger catalogue that they are now selling "babbit solder" page 586, for lining bearings

- ravenscraft - Wednesday, 12/19/07 08:52:13 EST

Bill: From the info you have given, I cant tell the dimensions of the inner chamber but I am guessing its at least 4" dia which is too large for such a small heat source. Also, 1" of Kaowool is probably not enough even for such a small forge. So I suggest that you add at least another layer of wool. Also, of the chamber is completely open at the entrance, you will lose a lot of heat through the mouth of the forge. You need to block this up so that there is just enough gap for the exhaust gas to flow freely and to get the work in and out. Try cutting a 1" strip of wool and coiling it up inside the mouth. The angle of the burner is not that critical but its generally more efficient if it is aimed tangentially so that the gas swirls around the walls before exiting.

adam - Wednesday, 12/19/07 10:34:02 EST

Boots: Miles, The last pair of really good boots I had were made in AMERICA and bought in a mall hiking store about 30 years ago. . . While they did have rubber soles and I would occasionally get a puff of rubbery smoke they were the warmest most comfortable footwear I have ever worn. They were leather lined and insulated between the layers of insulation. The first season I wore them was severely cold and wet and I had nice warm feet all winter. . . and when your feet arm pleasantly warm so to goes the rest of you. The type of socks worn with these boots made little difference. In fact I wore cheap thin socks because the boots were almost too warm.

I cannot remember the brand (something simple like Forester or Rocky Mtn) but I am sure they are long gone as I have been looking for a replacement pair. I wore those boots most of the year for about 20 years. Since I could not find the same brand I spent a lot of time looking for leather lined boots. All I found in the common stores in our area were cheap single layer (unlined) boots almost always made in Korea. I gave up after a couple years of looking.

- guru - Wednesday, 12/19/07 15:19:51 EST

I used to know a number of folks with Rocky boots, which seemed to have a good reputation. Can't say where they're made, or if the reputation is still as good. Some are leather lined. http://www.rockyboots.com

I have a pair of Danner Ft. Lewis boots, outrageously expensive even fifteen years ago. Excellent boots, but at zero degrees F even those won't keep my feet toasty when I'm just standing around for long periods. And yes, they have rubber soles.

Matt B - Wednesday, 12/19/07 15:52:06 EST

What is the approximate value of a 1929 Solderfors 123# # 8 anvil. It is in very good conditions but there are no accessories.

Scott Miller - Wednesday, 12/19/07 20:07:16 EST

Scott Miller-- I have a near-kin to that anvil. It is one of the best ever. Solid cast Swedish steel. Don't sell it.

Miles Undercut - Wednesday, 12/19/07 20:31:26 EST

I bought a pair of snowmobile boots when I lived in Canada. Knee high, rubber bottom and nylon uppers. 1/2" felt packs. Kept my feet toasty warm to -40C. It might work to a lower temperature but that was as cold as I cared to venture out in. I wore a goose-down parka with a snorkel hood with those boots and never got cold.

quenchcrack - Wednesday, 12/19/07 20:34:26 EST

Nonsense, Scott. That anvil is worth at least $50. I will pay you $75 cash money and even pay the shipping. :-)

quenchcrack - Wednesday, 12/19/07 20:36:06 EST

Thanks, y'all-- Rocky doesnt make an insulated boot large enough for me. Doris Shyda, owner of Shyda's sporting goods in Lebanon, Pa., and an experienced hunter, says I need Danner Quarrys, at $200-plus, says their steepness is accounted for by vastly superior quality. Two sons, who do a lot of winter hunting (one is a veteran game warden), say forget insulated boots, just get thermal sock liners inside waterproofed boots. I am pondering.

Miles Undercut - Wednesday, 12/19/07 20:38:37 EST

You know, in my limited experience electric socks are hell for walking. But for just standing at an anvil in the bitter cold . . .

Matt B - Wednesday, 12/19/07 20:59:01 EST

I have a 40 t0 1 dividing head and am looking for a division chart showing the full turn and partial turn. Any help would be appreciated.

Kevin - Wednesday, 12/19/07 21:02:44 EST

The best made work boots I have ever seen or used are made in a small factory in Britain. They offer leather lined, steel toes and any type you would ever want but they are not cheap! If you cost a good boot (or tool or anything else) over it's useful life though they are actually the best investment you can make.

philip in china - Wednesday, 12/19/07 21:26:01 EST

I have just found the boot maker on the net. www.williamlennon.co.uk Their site is worth a visit!

philip in china - Wednesday, 12/19/07 21:27:20 EST

hi have a 325lb bridge anvil on ebay

john a brinkman - Wednesday, 12/19/07 21:44:35 EST

John Brinkman,

And your question is...?

vicopper - Wednesday, 12/19/07 22:01:41 EST

Solderfors Anvil: Scott, Condition means a lot and what some consider good is "in one piece". But in good condition in the range of $3 to $5/pound depending on the location and how big a hurry you are in to sell it.

- guru - Wednesday, 12/19/07 23:30:38 EST

Kevin: The formula is T=40/N. The hole plates should be from 15 to 49 holes. T is the number of turns and fractional turns, N is the number of divisions You want to cut. You work this as fractional turns. I will try to give an example, but I havn't done this in over 30 years. To cut 12 teeth T=40/12. T=3 4/12 there is no 12 hole plate, but there is a 24, so You would use 3 turns and 8 holes on a 24 hole plate. Each tooth gets 3 complete turns + 8 more holes. That is what the wings on the plate shaft are for. You set them for the 8 holes.

- Dave Boyer - Wednesday, 12/19/07 23:30:46 EST

40:1 Dividing Head Kevin, I have an old one of those that takes change gears for turning spirals on a Cincinnati mill. . . I spent a week doing calculations for the angles based on the number of holes plus turns on the dividing plate and made a nice wall chart. Great exercise in mathematics and logic.

THEN, I found that there was a chart including all the change gears for machining spirals in Machinery's Handbook.

A 40:1 dividing head is the industry standard. Normally they come with double sided dividing plates. Sometimes they have several and sometime they are missing. .

1/40 of a circle is 9° (the same a single full step in a stepper motor). So ten turns is 90°, five turns 45° (or an 8 hole circle). Then using the dividing wheel 2.5 turns is 16 places, 6-2/3 is a 6 bolt circle and 3-1/3 a 12.

When doing repeat moves counting places like 20 holes in a 60 hole plate to get 1/3 you adjust the dividing wings once then use them to place the pin in the hole for the odd amounts.

A proper wheel set will let you make gears up to 400 or more teeth and every whole number below. For some numbers the math is mind boggling. Early wheel sets were made by hand with dividers. Due to the 40:1 reduction a hole could be off .010" and only effect the outcome by .00025" at the same diameter as the hole circle on the wheel. However, it is possible to make hand laid out dividing wheels accurate to much closer tolerances. If you layout a large diameter wheel by hand then use it to make smaller wheels you have greatly improved your accuracy.

Always check Machinery's Handbook first!

- guru - Wednesday, 12/19/07 23:57:54 EST

Hmmm, I used too many holes in my example for thirds. . .

To make that 15 hole circle on the plate takes 2-2/3 turns. So a hand made plate divided by 6 (a hex checked with a compass) can make the 15 circle.

To make 17 requires some multiple of 17 such as 34. But to make 18 requires 9ths and this leads to may others. 19 requires 38 holes. 40 holes gives you 4,5,8,10's and many others.

It is interesting to play with and backing out the whole number steps can be a puzzle.

Where is can get really weird and few do this. . You can use X/N1 divisions + X/N2 divisions. . .

- guru - Thursday, 12/20/07 00:33:27 EST

Re insulated comfortable boots, check out Steel Blue, made in Western Australia and sold in the US. www.steelblue.com.au

Terry M - Thursday, 12/20/07 06:15:39 EST

Best boots I found for standing around in the Bavarian Wilderness were the army waterproof cold weather boots with a good medium weight polypropelene sock to wick away any moisture that was a result of sweaty feet. Water proofing works both ways and dosen't let your feet breath well either. These boots are available at your local army surplus store and aren't generally too expensive. They use goretex and a heavy Vibram brand rubber sole that dosen't melt too easily.

Robert Cutting - Thursday, 12/20/07 07:59:38 EST

Thanks, guys!

Miles Undercut - Thursday, 12/20/07 09:17:14 EST

I'm looking into buying a premade gas forge and would like to get some professional advice on which one would be best.(Sorry,I bet you have been asked this question a thousand times).One uses ceramic replaceable liners and one uses k-wool replaceable liners.Thanks!

ringer - Thursday, 12/20/07 09:37:51 EST

Ringer, what and how much do you plan to use this forge for?

Ceramic liners usually take longer to heat up and cool down but have better "throughput" they also resist wear and tear better and so are great for production work.

Kaowool lined forges are usually faster heat-up/cool off but are a little more delicate and so make better hobby forges.

Without knowing *YOUR* details can't say which would be best

Thomas

Thomas P - Thursday, 12/20/07 10:36:57 EST

Ringer, More. . . Forges can be heavy requiring a fork lift to move or be light weight to where one or two people can handle one easily. The difference is the refractory. Portability is often a major concern in a small shop.

- guru - Thursday, 12/20/07 12:23:32 EST

Isn't there an issue of fuel efficiency, too? In a cermic wool lined forge less fuel is being wasted on heating the forge lining. No?

Matt B - Thursday, 12/20/07 13:14:48 EST

It depends on how the forge/furnace is operated. Light weight forges heat up quick and stay relatively cool on the outside. Steel put into them reduce the temperature significantly. For short jobs and intermittent work they are the most efficient. They also cool down fast so they can be moved sooner after use (part of being portable).

Heavy lined forges absorb a lot of heat and are affected less by introduction of cold steel, but they ARE affected. They are generally more durable. If well built and run nearly continuously their overall efficiency is not much different than the light weight refractory forge. However, the long hours of use indicate a LOT of throughput (more than most small shops need). Even after shut down for several hours a heavy forge may still have a red glow. It can take days to be cool enough to move or work on.

Lots of pros and cons.

- guru - Thursday, 12/20/07 13:33:06 EST

Hello, I finally made it back. Thanks for the information Thomas,Matt,and Guru...The ceramic lined forge I am looking at is portable and weighs less then 70 pounds.It has two burners that can be controlled independently want to do some production work and hope to learn some bladesmithing in the future.The kaowool forge is the Chile Forge with two burners.

ringer - Thursday, 12/20/07 18:54:21 EST

Ringer, If you plan on feeding a forge all day, say to work with a power hammer I would go with the more durable forge. Even the hard refractory floor will wear from sliding billets in and out all day.

- guru - Friday, 12/21/07 00:03:58 EST

Ringer: I am just rephrasing what others have said. You have to put a lot more heat into a ceramic liner to get it up to temp. It may take 40 mins to get to welding heat. Once at temp it will hold its temp better than a kaowool forge and not be chilled by cold work. If you run the forge all day then the investment in time and fuel to heat the liner is worth it. However, if you just want to forge for a couple of hours in the evening after work its very inefficient. It will take a long time to heat up, soak up a lot of fuel doing so and then be shut down shortly after. Furthermore, if you are not on a treadmill as in a commercial shop, you can afford to take your time and be careful about how you get the work in and out of the chamber so as not to damage the liner.

adam - Friday, 12/21/07 12:29:56 EST

I highly recommend the micro forge, so easy a caveman could do it.

- Nippulini - Friday, 12/21/07 18:34:21 EST

Please i need some information of my power hammer "hartenfels" Thanks

carlos - Friday, 12/21/07 19:15:05 EST

Need Advice on First Anvil

My apologies if this subject was recently covered; it is impossible to do any kind of search that includes "anvil" on this forum.

I have been involved in various metalworking trades much of my life, but have never really done any hammering on hot iron. (Among other things, gunsmithing, and I once built custom racing bicycles plus all my own jigs and fixtures.) It's been nearly ten years since I sold my last shop; I've decided I miss the smell of hot metal and want to try my hand at blacksmithing, just as a hobby sort of thing to start. I've still got most of the non-specialized hand tools, and picked up a MIG welder a couple years ago. I think I can make a pretty good gas forge for not a lot of money, that sort of thing is well within my skill set. So I need an anvil.

This part of the country (Montana) has always been pretty sparsely populated, and there aren't hundreds of the things rusting in old barns and being given away cheap. I don't want to look forever, and don't have the money to buy a great big fancy new one. After seeing what old anvils sell for on Ebay, I've just about decided to buy a "big enough for now" new one of decent quality, on the theory that if/when I decide to upgrade I can probably get most of my money back out of it. So far I've narrowed the search down to these three, all between 118 and 125 pounds.

JHM Journeyman, 125 pounds
http://www.equilox.com/JHM-Manufacturing-Journeyman-125-pounds-P82C7.aspx

Old World Anvils Two horn classic, 50 Kg
http://www.oldworldanvils.com/anvils/two_horn_classic.html

Euroanvils German Style 50 Kg
http://www.euroanvils.net/prices.php

I understand that JHM changed hands a couple years ago; they seem to be for sale everywhere at wildly different prices. I have heard they are not the same as they used to be. Does anyone have experience with their current production, or anything else to recommend for or against? I like the idea of buying US manufactured if in fact they still are. I don't care about the farrier's features, I am not going to shoe horses. I don't care much for the odd-sized hardie hole on the Euroanvil, and freight charges from the East Coast vs Midwest would push the price up a bit on that one.

Does anyone have input that can help me with this decision? Personal experience any knowledge of quality would be especially helpful. Anything about these anvils I should know, that I may overlook because of my lack of knowledge? Anyone have another suggestion?

Thanks in advance for your time.
Grizzly

Sparrow - Friday, 12/21/07 21:40:51 EST

Anvils: The JHM you are looking at is a nice farrier's anvil bit there is a huge difference between a farrier's anvil and a blacksmith' anvil. The mass is spread out in the horn and heal and they have a very small springy waist. They are hard to forge on compared to those with support under most of the face such as your other two choices.

The Old World and the Euro Anvil are made by the same foundries in the Czech Republic. Exactly who is casting and machining them varies according to how busy they are. In these two anvils the only difference is the reputation of the dealer and who you trust.

Personally I would go with the 175 pound Euroanvil for a little more money OR if you want American made a Nimba for even more.

For basics on selecting an anvil see out FAQs page, third article, Selecting an Anvil.

- guru - Saturday, 12/22/07 00:01:23 EST

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