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 August 1 - 7, 2012 on the Guru's Den
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RR-Rail anvils :
Thomas, look at our article on Making RR-Rail anvils

The reason all of these are turned on end is that rail is very springy and makes a lousy anvil for forging. But when you put the mass in-line to the blow, there is no spring and the mass becomes very efficient. YES, the target or work area is small but it is no smaller than the "sweet spot" on a 100 pound or so anvil where 99% of the work is done.

Grinding by hand can go pretty fast with a heavy angle grinder OR a small 4.5" angle grinder with a coarse fast cutting wheel. They make various types of wheels for these grinders. Long lasting wheels cut slow and are better for polishing than cutting. The fast cut wheels do not last long BUT replacing them often is cost effective compared to your time (no matter how you value it). I've seen smiths take 1/8" (~3mm) or more off the entire face of a large anvil with a hand held grinder. . .
   - guru - Wednesday, 08/22/12 21:59:04 EDT

As soon as a scrap metal project starts taking considerable time and consumables because of the condition of the scrap metal I start looking for a better piece of scrap metal!

Or to put it another way is spending $100 of grinding disks and time to get to the same state as another chunk of rail that cost you $25 a good tradeoff?
   Thomas P - Thursday, 08/23/12 12:03:00 EDT

Post vise Prices : Susan; the price on a post vise is quite location specific---they cost about twice as much where I live now than they did where I used to live---and both places are in the contiguous United States!

I can't say what price they are getting in Singapore where you live; or was it South Africa, the UK, Australia, Chile, China...

However the pricing is usually dependent on jaw width with 4" being a common size and 6" a sought after size and 8" quite unusual!

Condition is very important---especially of the screw and screwbox. Almost everything else is easily repaired on a post vise but a worn screw and screwbox is not---usually cheaper and easier to buy another vise in better shape than to make another screw and screwbox. So screws should have square threads, screwbox should not be missing pieces or have cracks.

The mounting bracket and spring are a nice bonus to make a "complete postvise"; but are quite easily made by a smith. I generally buy vises missing them as they sell cheaper and making replacements is a simple Saturday morning task.

Leg Vises with nicely made bevels on the legs often get a bonus in price because they are "pretty".

Last Quad State I attended there were probably 100 vises for sale there with the bottom price tier of around US$75
   Thomas P - Thursday, 08/23/12 12:15:01 EDT

Rail anvils : If you are determined to have a rail anvil, consider steel mill overhead crane rail. I have had pieces of some pretty hairy rail with purtnear 3 inch thick webs on them. Like main line railroad track, they will work harden under traffic. Every chunk of it I ever brought to SOFA didn't stay on the tailgate for long. I have one 3 foot chunk, but since I've retired from the mill, I doubt I'll get any more. So its disposition will be up to the executor of my estate,I reckon(grin)
   - 3dogs - Thursday, 08/23/12 17:37:11 EDT

Heavy Rail :
I was sent a (poor) photo of some extra heavy rail some time ago. It had no "web" just straight sides and small flanges - almost a square section. I estimated that it was 250 pound rail (pounds per yard).
   - guru - Friday, 08/24/12 10:01:07 EDT

Rounding Hammers : As a general rule how much crown should a rounding hammer face have, and what are they good for?
   Greg - Friday, 08/24/12 12:43:19 EDT

Well my general answer for that sort of question is "It depends on what YOU are going to do with it and what YOU like in a hammer". Some folks like a nearly spherical crown because they use them for dishing; some folks like a quite flattish crown; some in between.

Personally I have several of differing crowns and use the one most suited to the job at hand---like hammering on the very edge of a knife blade that's flat on the anvil to pop a spot on the edge that's back of the rest of the edge out.
   Thomas P - Friday, 08/24/12 13:47:41 EDT

Hammer Face Radius :
This varies a lot. I determined the face radius on my favorite sheet metal hammer was around 28". On another it is about 36" (quite flat). On common forging hammers the radius can be as small as the length of the hammer (pien to face) or less. Then you get into rounding hammers which are half way between forging and a ball pien. So the radius is less than half the hammer length (2 to less than 1").

When I went to look at my favorite forging hammer it was so flattened and mushroomed it was impossible to put a specific radius on it. It had worn into a very flat oval. My heavier hammer which shows no mushrooming is also worn flatter than when new.

As Thomas noted, it all depends on the use and what you want.

I've inherited a couple rounding hammers and have yet to find a use for them.
   - guru - Friday, 08/24/12 14:02:36 EDT

OK. I was just wondering the general rule that makes one a rounding hammer and another a forging hammer. I assume the rounding hammer has more radius to it as a general rule and depending on the need at hand. Why is a rounding hammer also known as a farrier's hammer? For fullering inside horse shoes?
   - Greg - Friday, 08/24/12 17:00:51 EDT

Hammer Face Radius : OK. I was just wondering the general rule that makes one a rounding hammer and another a forging hammer. I assume the rounding hammer has more radius to it as a general rule and depending on the need at hand. Why is a rounding hammer also known as a farrier's hammer? For fullering inside horse shoes?
   Greg - Friday, 08/24/12 17:01:17 EDT

Burning in a Tang : I have tried burning in a tang into a piece of cherry with some luck, but need advice. My tang was just square stock (3/8) with a pointed end and I heated up the last inch or two to a bright red heat. I had pre-drilled a hole slightly smaller than the tang before hand. The burning process was very easy, only took 2 heats to burn through about 6 inches of wood. Afterwards though the hole was fairly charred and wider than the tang due to burning. This was very aggravating because I was expecting it to be a tight fit and ended up putting rivets in which I was trying to avoid.

What is the proper way to get a tight fit with this procedure? Was the tang too hot? Should I have flattened the tang? Tapered it? Thanks in advance.

-Eric
   - Eric - Friday, 08/24/12 17:33:52 EDT

Eric, First, if it went fast and easy the tang was much too hot. Wood and paper char at a little over 400 degrees F. For a snug fit you needed just enough heat. If a pilot hole is used then the last inch or so should be a force fit not burned out. How much depends on the type of wood and how much compression it can take.

This type of tang should taper from about 80% of the blade's height to around 1/4" in height and the thickness of the blade. Fitting into a blind hole goes slow. When finished the blade can be bedded into epoxy to make it tight. This is done at the same time as upsetting the tang into the pommel so everything is tight and permanent. Other glues could be used but any with water or other solvent that lets the glue dry and shrink are not a good choice.

Other ways the make a tight fit on a tapered tang is make the hole larger on the small end of the tapered sides then wedge it with hard wood and glue.
   - guru - Friday, 08/24/12 17:47:51 EDT

They just keep on bringing them in. . . :
Valley Products Anvil
Click for detail


A photo is worth a thousand words. Purchased on ebay for $2/pound plus shipping - about double most Chinese iron. For more see Cheap Cast Iron Anvils and Ebay Fraud, ASO's on ebay
   - guru - Friday, 08/24/12 18:09:38 EDT

A traditional cutler's cement can help bed a tang securely;

The primal metal smithing folks use conifer resin melted and mixed with PHD, (Powdered Herbivore Dung), the hot tang melts the mix which then sets up tight.
   Thomas P - Friday, 08/24/12 18:15:10 EDT

Primal cement : Ahhhhh! Nothing quite like the aroma of burning pine sap and bull poo to get the sinuses open. Quench the blade in stale pee for the whole "natural" experience. Who needs modern methods?
   - Rich Waugh - Friday, 08/24/12 19:53:35 EDT

Natural Cements :
There are some advantages to natural cements that are heat sensitive. Musical instruments are traditionally assembled with hide glue (actually made with hooves). This gives them the advantage that they can be disassembled for repairs with a little heat. Pine resin cement is similar in that it can be softened with heat.
   - guru - Friday, 08/24/12 21:54:35 EDT

Rounding Hammer : Check this link, best description I have seen yet.

http://www.youtube.com/watch?v=pCiMitLk5GI&feature=share
   - Dave Boyer - Friday, 08/24/12 23:18:44 EDT

Power hammer stroke : How do I determine the length of the stroke on the power hammer I am building? What factors are involved and what components are most affected? Is there a simple equation or formula?

Thanks for any help.
   - Bill - Saturday, 08/25/12 00:23:53 EDT

fyi-us anvil : the small us anvil i sent a pic of ended up being cast steel-i drilled a small hole in the underside and got a spiral shaving
   vern - Saturday, 08/25/12 12:04:08 EDT

Vern, Forged steel also produces curling chips.
   - guru - Saturday, 08/25/12 14:22:56 EDT

Power Hammer Stroke :
Bill, What kind of hammer? Utility air, Helve, Bumper Helve, Spring Helve, DuPont Coil Spring, DuPont Leaf, Self Contained Air, Hybrid Air/Mechanical?

Most mechanical hammers operate at 2.5 to 3 times the crank stroke or less depending on the stiffness of the springs. About 10% of the additional travel is between at-rest and the balance in over travel at the top. Upward travel is limited by the length and angle of the toggle arms with 45 degrees being the normal maximum angle (but it could be more with a weak spring).

When toggle arms are too long you get a "sloppy" motion that is hard to control that takes a very heavy spring (as on Little Giants). A shorter toggle gives you better control with a smaller spring (like on a Fairbanks/DuPont). Too short a toggle and you get no increase in power from the return stroke.

Generally in a DuPont type arrangement the spring force needs to support the mass of the ram with no more than 5 to 10 degrees of sag in the toggles. This means about 9 to 50 times the ram weight at the toggle ends or MORE with longer toggles (I botched this calc but it worked OK in my hammer). If the toggles have extra mechanical advantage produced by the link arms then the spring needs to be stronger by the divider of the arms (about 2:1).

Every linkage type has a different mathematical model that would have to be expressed in more than one formula with numerous variables. Variables for a DuPont style linkage are, ram weight, toggle arm length, Link arm multiplier, Maximum Speed, Max Toggle Angle.

When I designed the X1 Hammer I used a 7 degree at rest toggle angle for two 4" toggles and a 110 pound ram. This resulted in needing 3500 pound springs cut in two. . .

See Power Hammer Linkages for examples of different types.

   - guru - Saturday, 08/25/12 15:10:11 EDT

Vector Formulaes :
I've worked on these several times for power hammers but it has always been for a part or piece. I'll see if I can put together a set of diagrams and rules. . . Its been since high school that I did any vector math with proofs. . . (over 40 years ago).
   - guru - Saturday, 08/25/12 15:23:24 EDT

Power Hammer Stroke : Sorry for the lack of description, Guru. I have been considering a design you call a "pogo" mostly because I have very limited space and it seemed to take up less room than other linkages. However, now that I've taken a look at the PH Linkage page, I think either the Brdley Compact or the Demsey Ram Coil would be better options for my skill level. I'm still working with a ram that will weigh around 20lbs and these two designs look like they would carry that weight easily. My concern with either of these designs is what kind of springs to get. Will I need to special order them or could I pick up useable springs at the hardware store or auto part shop? What do I need to avoid when selecting springs and what are indicators that I have found what I need?

Thanks again and thanks especially for the explanation of the toggle and spring mechanics.
   - Bill - Saturday, 08/25/12 16:48:53 EDT

Both the Ram Coil and rubber band hammer are unproven (logically and on paper they work) but I would lean toward the rubber band hammer using nylon twine for the elastomer. While it sounds like a strange elastomer it is similar to the twisted rope springs on some catapults except that nylon is much springier than most natural fibers. The advantage is you can just keep wrapping more and more string. Be sure to use twisted string rather than braided.

While the Ram Coil looks easy it needs the heaviest coil springs that will fit in about 4 to 5" on each side AND they need to be preloaded a BUNCH, maybe 30% of their rated stretch. Their are various hardware suppliers like McMaster Carr that have a wide range of such springs.

Coil springs are also notorious for failing catastrophically and sending parts flying. You want some kind of guard around them.

The general parameters for a 20 pound hammer would be to plan on the dies being open about 1/2 to 3/4" at rest with the spring sag of about 5 degrees. That is your starting point. The the stroke of the hammer would want to be about 4" (the crank being 2" off center). Then you figure out the parts inbetween and thus the height of the crank. The vertical stroke from at rest to maximum upward travel would be the 4" plus travel due to spring/toggle travel. This is a max of about 40 to 45 degrees angle thus doubling the stroke. You need to keep the ran in the guides for this distance PLUS any height or stroke adjustment you may build in (not that many DIY hammers do not have either but should at least have a height adjustment).

If you build an untested mechanism I would plan on it running slow for its size (maybe 200 to 300 blows per minute max). If it works well then you can speed it up.

While a 20 pound hammer sounds like a very small machine it is still a serious machine. A friend of mine recently built a 30 pound hammer to do a high production job with lots of small pieces. He figured that at his age a million strokes of the hammer might end his career OR he might not be able to complete the job. During testing with square cornered (very inefficient) mild steel dies the hammer would rapidly chew up 1/2" bar and is probably more then adequate to forge larger bar (maybe 3/4"). Another friend does small sculptures and while our 110 pound X1 hammers have good control it is tricky free form forging parts that are often 1/4" (6mm) or so. Thus we are planning a much smaller hammer,
   - guru - Sunday, 08/26/12 12:36:04 EDT

Power Hammer Springs : I have greater confidence in my ability to make the coil springs work than I do in getting the nylon twine to work. I had already planned to put a sheet metal guard over the springs. I've had one break in a similar stress situation and it was lucky for me I was wearing safety glasses. Thanks for the warning, though.

I think I could make a hinged bracket with a bolt run through it to open the arms and tighten the springs once the linkage is mounted to the drive shaft. My main concern at this point is making everything strong enough to perform without undo risk to me or anything else in the shop. The more weight I put up top the greater the need for stiffening and ballast on the frame and the base.

One other thing I wanted to ask: My shop floor is dirt so I have no way to run anchor bolts through the base with any expectation of them holding. I am hoping that I can simply pour three or four footers about eight or ten inches in diameter and about eighteen inches deep rather than pouring one large plate of concrete. Do you think the three would hold up under the sort of vibration a PH will generate? I might even go so far as to link the footers with rebar if it would help the overall integrity.
   - Bill - Monday, 08/27/12 16:57:22 EDT

Bill : The best way to keep a power hammer from jumping all around is to use enough anvil mass.
   - Dave Boyer - Monday, 08/27/12 21:46:34 EDT

Concrete :
Bill, What you described is 448 pounds of concrete or a square yard over 4" thick. A single slab is a known quantity, the type of soil and its uniformity at depth is an unknown. The problem with the individual footings is that one or more could be on soft spots and one or more on hard spots. Very strange things can happen.

A single 18 x 36 x 9" foundation block would probably be better.

Another way to build a hammer foundation is out of wood. A 48" square or more wood pad 6" thick sunk level with your floor will "float" a lot of weight and provide a lot of lateral support (weight about 300 to 400 pounds). You could combine that with putting your concrete in the frame of the hammer. . .
   - guru - Monday, 08/27/12 21:58:14 EDT

Chimney : Hello, im building a suspended hood for my coal fired forge and i was wondering about an adequate size chimney, im welding the chimney and itll be square, i was gonna go 12in will that be adequate or too big?
   - Lee - Tuesday, 08/28/12 12:41:15 EDT

Suspended hoods must suck up ALL the air at their huge opening. All that cold or room temperature air dilutes the hot air and reduces stack efficiency. To work properly this requires a large or very tall stack. 12" diameter might do it but I would want at least 16" or larger.

The stacks you see in many old school and large shop photos with over head hoods either had very large stacks OR a fan exhaust system. Almost all the school systems had forced draft.

Today most smiths use side draft hoods that suck in mostly hot smoke and very little room air. These require a minimum of a 10" stack with a 12" recommended. The only time smoke escape these is when starting a fire or if there is a significant draft across the forge. To eliminate startup smoke many smiths toss a piece of lit news print into the hood to start the draft.

   - guru - Tuesday, 08/28/12 13:40:52 EDT

Coal Supplier update : Dear Guru,

Just wanted to let you know that People's Coal in Cumberland, Rhode Island went out of business about 7 or 8 years ago now. Sad way to update your coal supplier list in Blacksmith Gazette, but it'll save disappointment down the road. Aubuchon Hardwares (in New England) carry bituminous coal for blacksmithing. Aubuchon Hardware stores are scarce in Connecticut, (I think there are just 2) but are more plentiful in Massachusetts, Vermont, New Hampshire, and Maine. Here's a store location link that might be helpful to New England smiths. http://www.hardwarestore.com/Store-Locations.aspx#Connecticut

Truly,
Jim Tomlinson
Old Hand Forge, Prospect, CT
   Jim Tomlinson - Thursday, 08/30/12 22:43:35 EDT

Jim, Will update. Long before Fred gave up the Blacksmiths Gazette he stopped updating the coal list. This was a good while before I took over the maintenance. So I'm sure there are a lot of errors in the list as it stands.
   - guru - Friday, 08/31/12 12:48:03 EDT

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