Self portrait (c) 1989 Jock Dempsey WELCOME to the Guru's Den!

Ask the Guru any reasonable blacksmithing or metalworking question and he will answer your question, find someone that can, OR research the question for you.

This is an archive of posts from April 26 to May 3rd on the Guru's Den

I have recently just made 4 pair of 60" long mild steel tongs that are used in a hot galvanized dip tank. The tank, I'm told, gets up to an excess of 800. Three (3) pair of the tongs have been returned to me broken. The fourth pair were not broken because they were not used. I have made tongs in the past for a few drop forge companies. I have never had any come back within a reasonable amount of time broken. As you know, tongs do wear out. My question is if I use an alloy, which alloy would you suggest that would withstand 800 plus temperatures? I'm assuming the tongs are breaking due to the temperature of the dip tank, or could the breakage be due to a direct other result in the galvanizing process?

Bruce R. Wallace -- Walmetalwk at - Sunday, April 26, 1998 at 17:01:47 (GMT)

BRUCE: Good question. I may have to do some research on that one. First I need to know what grade or alloy you are currently using and where the tongs are breaking. I'd also be curious to know if they are repeatedly shocking the tongs by quenching them.

The liquid zinc will dissolve the steel over a period of time or through continued usage. I've used steel crucibles for melting zinc and a 1/4" (6mm) wall will be dissolved through after about 20 melts! The tongs may look OK but be weakened by internal corrosion.

We may have to find a material such as a stainless alloy that is resistant to the zinc.

You could make the part that is exposed to the zinc out of the more expensive alloy and weld carbon steel reins to them.

A few more details and we may find a solution.

-- guru - 04/26/98 17:28:56 GMT

I'm making the tongs out of hot rolled mild steel. The same as I make all my tongs from. The tongs do have arc welded mild steel reins. The welds them self have not broke, but the tongs have broke close to the welds. The tongs have also broke no where near the welds. The strength of the welds have not been compromised by grinding them to look good. The tongs don't have to look good they need to work good. Some further investigation on my part may be in order. I just find it strange that these tongs are coming back broken. It wouldn't be so unusual if one pair was returned. Hit me in the head with a hammer some things up.

Bruce R. Wallace -- Walmetalwk at - Sunday, April 26, 1998 at 18:21:26 (GMT)

I've seen old tongs break at the forge welds but it is very rare to see anything made out of steel break unless it is either too brittle from quenching OR it has been repeatedly yielded in service. Then you have a cyclic fatigue failure.

Try this test: Take a sample piece of the tongs, heat to a dull red and quench. Check the hardness by trying to bend in a vise. If the sample breaks the "mild steel" may not have been as mild as you think and either you or the customer may have quenched the tongs and the fracture was inevitable.

Then take another sample from near the fracture and try to break it in the vise (do not use heat to change the temper).

If the steel passes both tests then I would suspect that someone tried to "adjust" the shape of the tongs cold or abused them in some other way. The worst that should have happened is that the tongs bent and had to be returned for straightening.

Another way to tell if the steel were too brittle (hard) is by the shape of the break. Brittle fractures occur in a twisted plane. You've broken drill bits. That shape. Then the question is who made them too hard, you or the customer.

-- guru - 04/26/98 18:51:29 GMT

How do you calculate a spiral on a hemispherical surface?

Michael asks: - Sunday, April 26, 1998 at 19:55:41 (GMT)

Calculating a spiral on the surface of a sphere requires calculus (I'm pretty sure) or a computer program. I've written complex shape computer geometry programs but not on a spherical surface.

You have two options that I'm aware of. One the computer program (I'll keep the problem in my future ideas file).

The other is a scale model. Get a ball, any ball. Draw the spiral on the ball and tape a piece of string on the spiral. Remove the string then measure it. Now comes the math.

Take the diameter of the two spherical surfaces Dl and Ds (large and small)

Divide Dl by Ds:

This returns your scale factor or multiplier (I'm assuming the model is smaller than the finished product). THEN multiply the measured model length by the scale factor Sf. This will be the length of the bar to start plus or minus any drawing out or rolling up of the ends.

NOTE: The scaled up size (the large sphere) should not be measured on the surface as the model is, but at the center line of the bar to be scrolled. Just take the diameter and add one bar width.

Calculation problems of this sort and computer solutions to them will one of the many future features of anvilfire

-- guru - 04/26/98 20:01:45 GMT

BRUCE: I just noticed that the temperature range that your special tongs are being used at may be smack in the middle of what's called the "blue brittle" range, 300F to 700F. In this range steel is weaker than at any point above or bellow (Tempil Guide to Ferrous Metallurgy). This may be a factor in your tong breakage problem.

However, there is still the possibility of some type of abuse.

-- guru 04/26/98 21:03:37 GMT

Do you know the formula to convert gallons to cubic feet. I have a round receiver thank for my 250Lb. Chambersburg. I wouldn't have any trouble figuring this problem out if the tank was square. I need 20 cubic feet of storage to operate the hammer efficiently. I know the compressor can do the job. The hammer needs 65cfm and my compressor delivers 165cfm.

Bruce R. Wallace -- Walmetalwk at 04/27/98 00:50:22 GMT

Tanks with elliptical ends can be tricky if you want an exact number. For rough estimates measure the length and include 1/4 of each head. It is easiest to keep all the units the same so measure in feet and convert to decimals of a foot (guess if you want).

Then Volume = 3.1416 * (Diameter/2) ^ 2 * Length.

PI times the radius squared times length.

If you measured in Feet, the answer will be in cubic feet.

-- guru Monday, 04/27/98 02:25:47 GMT

Thanks Guru. I knew I could count on you. This is the only place on the web I could get a straight answer, FAST. Keep up the good work. Oh yeah, BTW this is a great page.

Bruce R. Wallace -- Walmetalwk at Monday, 04/27/98 03:33:45 GMT

Hey Jock!!I really think your new site is like The Junkyard in format but different because it is yours.By the looks of things it is already a success. What do think of building a home made metal cutting bandsaw by using the directions from the book,"Designing and Building a Metal Cutting Bandsaw".Written and illustrated by Vincent R. Gingery.Do you think it would be as strong and accurately cutting as they say.

"THE BUB" -- hagiumet at Monday, 04/27/98 07:59:48 GMT

SHOP BUILT BANDSAW: I haven't seen this particular book but I am familiar with a few of Gingery's other books and he is very good at reducing things to basics and presenting clear plans.

The most important part of a metal cutting bandsaw is the guide system. It is fairly simple to make but requires ball bearing rollers on the cutoff type saws that twist the blade so that long work can be put under them. I have an old Ridgid band saw that uses bearings about 1-1/2" in diameter mounted on eccentrics so that they can be accurately adjusted. I had to replace these bearings when I bought the saw (used). In 1977 the (6) bearings cost me $70 US. If you cut costs too much in this area you are bound to have trouble.

The frame and base should be fairly rigid (no pun intended). My saw being such a great tool my Dad decided to buy one for his shop. The department store brand looked identical to my saw. When we got it home and unpacked it turned out that the cast iron table/base had been replaced with pressed 1/8" steel plate. This saw never performed as well as the original Ridgid brand saw that has been copied by manufacturers all over the world. I have seen these "knock offs" selling for as little as $300. DO NOT BUY them, it is a waste of money even at that price.

Building your own saw is an interesting project and it could perform as well or better than many commercial saws. However, this type of tool requires significant abilities as a craftsman. Loose fits on the head pivot, or sloppy wheel alignment can make the project a failure.

If you build it, take photos as you go and we will run an article on anvilfire!

-- guru Monday, 04/27/98 11:20:47 GMT

OBTW - This page may have some vague similarities with the other page you mentioned (both have blacksmithing as their subject) but anvilfire has something no other web page has, a full time guru to answer your questions and provide content. On that "other" page you might get your question answered. For over a year I answered almost all questions on that page. Now I do it here and may no longer post on that other page (not my decision or choice).

In the future we will be adding metallurgical charts and graphs, complete sets of plans, on-line calculators and materials databases just to name a few items! Check in Friday May 1st for our BIG announcement during our official Grand Opening!

-- guru Monday, 04/27/98 11:31:31 GMT

Say Garu or all Garues, Would it be worth while to take old ball bearings out of their races and anneal them so I could drill them for a project or would it be cheaper to just buy them already annealed.I have a free access to discarded bearings,from the machine shop at owr work. I have searched the web book stores and can not find,"Decorative and Sculptural Ironwork,by Donna Meilach.Could it be the book is out of print or a very recently published.

BUB -- hagiumet at Tuesday, 04/28/98 05:27:19 GMT

The Donna Meilach book was published in 1977 by Crown Publishers. If it is not in print it should be. I was getting ready to publish a review of this landmark work. . . Maybe I should go ahead and perhaps the publisher will notice the demand. Have you tried Norm Larson, he may have some inventoried?

Plain steel balls are pretty cheap from McMaster-Carr.

Wood ashes, quick lime or plaster of paris make a great annealing enviroment. Heat the parts and then bury in some of the light powder. They act as an insulator so the parts cool very slowly. The high alloy case hardened bearing parts need a slow anneal. Parts burried like this may take 24 hours or more to cool!

Sorry I didn't get back to you sooner. We are temporarily without local internet service (telco tech diff).

-- guru Tuesday, 04/28/98 14:34:39 GMT

I'm planning to build a Little Giant type power hammer (about 40 lb), since there is no way you can buy one new or second hand here in South Africa. I've got a design for the clutch, eccentric, hammer guides, etc pretty much sorted out, but need some guidance on the spring. I'd rather not go the coil spring route as in the Little Giant but go for a leaf spring arrangement as in some other makes. Do you have any rule of thumb guidelines on size of spring, number of leaves, etc. I'll forge up the spring myself from 5160 and can play around a bit, but I'd like to start off in the right ballpark.

tom nelson -- tom.nelson at Tuesday, 04/28/98 19:07:50 GMT

LEAF SPRINGS are a tricky to design and require some trial and error. However, trial and error on paper (or the PC) is easier than making a lot of springs that don't work!

You start with a plain bar and calculate deflection at a given load. On the type of design you are talking about the spring is ridgidly attached in the middle for some distance so the calculations must be done based on a beam fixed on one end, then double the capacity (or use half the load). In my Machinery's Handbook under strength of materials this is "case 11, Fixed at one end, Load at Other". The length would be measured from the fixed end to the center of the loop.

If you don't have a Machinery's Handbook, almost any other engineering reference will have beam formulas. Computer programs are also available for this type of thing.

I'd take a guess at a spring, say 2" x 5/16" and a foot of flex length. Basicaly what you want is a spring that the drive motor can compress or bend for the maximum thickness of the stock (plus an allowance) to be forged. Say 3" (a flat on edge). Use motor torque only, and do not take any flywheel affect into account. This will provide your safety factor! Take these numbers and run your calculations.

If the spring is over stressed (say over 70,000 PSI*), then make it longer or thinner. If this makes too soft a spring, make it wider or add leaves. The capacity of stacked leaf springs is based on the sum of the capacity of each leaf. If you try to make a single leaf replace a stack the stress goes up. Single leaves are generaly tapered in thickness to avoid high stress at the center anchor point. A tricky thing to do accurately enough to avoid creating more stress points.

If you choose to make springs by trial and error then remember the motor torque spring compression factor and test your springs with a scale. This won't tell you if the spring is over stressed but it will tell you if it will work without installing it on the hammer.

*The max stress for springs varies with the alloy used, the expected duty and the quality of heat treating. Machinery's Handbook also has a good section on spring design, although it covers mainly coil and torsion springs.

TORSION HAMMER SPRING. This is an idea I had a while back for the JYH and opted for my shock absorber link instead. A coiled torsion spring, with the coil wrapped around the crank pin, its double arms becomming the upper toggle links. The arms would have to be bent inward to put them on a common center line (or maybe not). The advantage of a torsion spring is that it has relatively low stree for the work it does. Think about it.

If the word pictures of the design parameters or my torsion spring idea are not clear to you, let me know and I will post a sketch or two on the plans page.

-- guru Tuesday, 04/28/98 20:35:47 GMT

What do you recommend for hammer die steel, I have talked with some folkes, they use the FX-2 die steel, (A Finkl & Sons Co.)
Some folks also say to use S-7 , 4140, 4350, H-13 etc.

I have a 110 LB air hammer, Sahinler SM-50 I would like to make a larger set of dies. How big can I get?? (how much over hang from the shank, dove tail)??
I would think a C 48 TO 52 maybe 55 hardness is what I need.
I do a lot tooling to use under the hammer, I don't want the dies to dent!!!!

I was thinking 3x5" maybe bigger, would like to do some tooling like Clifton Ralph does.

Glenn Horr -- ridgart at Tuesday, 04/28/98 21:40:50 GMT

I like large flat dies, then use either hand held or clamped (to the die) tooling.

I like H-13 because I'm most familiar with it. We use a brand called Viscount-44. The 44 is the Rockwell number that it comes pre-heat treated at. This is tough stuff but it CAN be machined in its heat treated condition if you run low speed or carbide tooling. This lets you avoid the heat treating of big pieces. Its not cheap. $200-300 for enough to make a set of dies.

On the other hand. I've made dies out of 4140 that worked great. I suspect any tool steel works if it is not too hard (properly tempered). The only advantage to the H-13 is that you can bring it up to low red heat and when it cools it will have not lost its temper!

Now, the brass tacks: I've seen a 100 feet of custom top rail forged out of 1-1/4" round in mild steel dies under a 350 pound Bradley hammer. They wore a little but it was mostly polish and places that should have been that shape in the first place!

I'll have to got look at the Saliner page but over-hung loads are generally a no-no. If you break your anvil cap with an oversized die the manufacturer will not stand behind any warranty you may have. You could probably go 1/2" extra on each end of the dovetail safely on the bottom die. As long as the top die is not actually working out on those edges it shouldn't be a problem.

-- guru Tuesday, 04/28/98 21:43:48 GMT

Dear old Wise One, I tried to find Norman Larson's book co,store,inc.,industries,unfortunitly I can not find their e-mail address.Syeeb,oh Syeeb please give me their e-mail address-please? Syeeb,Syeeb another question I have.Could you please tell me if there is a book out there,in the great sandy desert,concerning the cataloging of post drills.The names,diagrams etc.I just bought one from a freind and have no idea what I bought it for except to hang it on my shop wall for looks.Do you think they still have a use today with all the modern drill presses? I see that my sand is running out,so stay well and I hope to see you in the funny papers.

BUB -- hagiumet at Wednesday, 04/29/98 01:23:30 GMT

NORM LARSON BOOKS, 5426 E.Hwy.246, Lompoc, CA 93436
805-735-2095 - Tell Norm I said Hi!

Your second question should be put to Norm also. I don't know of such a book. Sounds like a good one for Doug Freund or Richard Postman. I'll publish photos of the machines as I find them or people send them to me but I've seen enough different type to know it would be quite a task.


If you don't have a metal working drill press in your shop (or electricity). I've drilled lots of holes with my (2) post drills and still use them occasionaly. Goto the 21st Century page, I wrote something on post drills just last week. They are very handy for jobs where drill breakage is a problem due to break through angles and such.

-- guru Wednesday, 04/29/98 02:57:15 GMT

I got so wound up thinking leaf springs I forgot to mention that you must also take the toggle arms into account. The toggles being in a straight line produce nearly infinite force on the spring at that point. The force drops off radically as the angle changes but will still be a huge multiplier. Again this becomes a good job for a computer program. The force vector formula is a simple function of the angle (sine or tan). I don't use it often enough so I generally need to look it up. If you can wait a few days I'll work up a diagram with all the parameters and formulae for a Little Giant type machine.

-- guru Wednesday, 04/29/98 03:49:55 GMT

DONA MEILACH BOOK: Decorative and Sculptural Ironwork , sadly is no longer available in print. Copies that are available may be selling at collectors prices but are still worth the price!

-- guru Wednesday, 04/29/98 17:06:46 GMT

Thanks for the whole raft of info on springs. I'll dust off my OLD books and try work up a solution. With the pointers you've given, I should come up with something reasonable to start with. I think I've got your idea on the torsion spring, but if there's a sketch or picture handy, it would help confirm I'm thinking right. I can't wait to get this hammer going, already got most of the big bits together. DEcided to start off with a 3 phase inverter variable speed drive on the motor, direct coupling via Vee belts, and play with speeds until I've got it all sussed out. Then I'll convert to fixed speed and put in a diff-based clutch arrangement. On the other hand, if the variable speed drive works OK, I may just stay with it. I've got a sketch done on CAD which I'd like to mail you sometime for comment.
Thanks again

tom -- tom.nelson at Wednesday, 04/29/98 21:07:39 GMT

TOM: Glad to look at your drawing. I can handle DXF's and DesignCAD DW2's. I think I can import from IGES.

I've been having trouble with my DOS DesignCAD products since I added memory to the PC. 3D doesn't work at all and the conversion utilities choke. First time I ever had trouble having TOO MUCH memory! Its only 32Mb. .
Is there a DesignCAD Guru in the house?

-- guru Wednesday, 04/29/98 21:25:20 GMT

TORSION HAMMER SPRING: For anyone that's intrested I've posted the drawing for Tom in Plans. This unique design application is probably patentable (or may have been in the past). The idea is now public domain.

-- guru Thursday, 04/30/98 17:01:23 GMT

Hey Guru! Where might I find good knife-making resource? Have you seen any info about either Kris or Barongs, which are double-edged long knives and short swords, respectively, for use in Phillipino weapons forms? I'd like to see if I could manufacture my own, but I have absolutely no idea where to begin!

Stu -- stu.smith at Thursday, 04/30/98 18:12:13 GMT

Start with your news stand. There are several magazines devoted to guns and knives. There you will find a variety of suppliers listed including bladesmiths that will sell you rough forged blades.

There are a number of good books on the subject. Knives and Knife Makers by Sid Lantham is one. Ask Norm Larson to put you on his mailing list (see address above). His new catalog is due to come out next month and it has books that you can find no where else. Norm will also make a recomendation if you are not sure which book is the best.

There are also some articles on very basic knife making in one of the Foxfire books. You will find them in your library and bookstore.

After studying some and you have a more specific question feel free to ask again.

-- guru Thursday, 04/30/98 18:38:19 GMT

Syeeb,Syeeb another question for the great Garu!!!! Is it possible that this could be the last sand storm for the month of april,98.A trick that i learned from another so called Wise man who obviously was an impostor. I see another storm on the horizon.Sorry but I must leave for the compounds of my tent,in Tent City.See you when the dust settles!

THE BUB -- hagiumet at Friday, 05/01/98 04:05:48 GMT

Ah, low gritty one, according to the GMT calendar the April sand storm season had past 4 hours 5 minutes and 48 seconds ago. . .

-- guru Friday, 05/01/98 04:11:00 GMT

Jock: Just found your site. Looks like it will be great. I'm looking forward to reading all the post. Like the idea of GMT as I'm a student pilot and have to think in Zulu time. Good luck. Mike.

Mike Sherman -- mmsher at Saturday, 05/02/98 02:49:00 GMT

OK, Jock! You've really got me going now!

I downloaded your tong instructions. They're great, and I'll try them tommorow.

BUT, you mentioned that Bealer's ART OF BLACKSMITHING tells a trick using brown paper as a temporary spacer when assembling the tongs.

I've got the revised edition. I've read the tong instructions five times this evening, trying to find the brown paper trick. I'll be a dirty name if it's in there, cause I sure can't find it. (grin)


Jim Wilson -- pawpaw at Saturday, 05/02/98 03:23:07 GMT

Mike: I wish I could take credit for it but my server runs on it! It does make sense on the internet but now I gotta' get another clock for the office. . . . Start to look like a TV news studio. Glad you found anvilfire!

Jim : You're NOT going to make me dig out my ragged first eddition and find that line are you. . . It had to be Bealer. "The Art" was my bible at one time. . .

A piece of heavy brown paper (like grocery bags used to be) is placed flat in the joint between the two halves of the tongs. Then when the rivit is inserted and headed, the paper burns (or falls) out leaving some clearance in the joint.

I'll find the reference and add it later. . .

-- guru Saturday, 05/02/98 03:36:59 GMT


My little Bradley arrived. Under the years of grunge this thing is perfect! It's going to be a showpiece! I love it. Only stands about 24 inches tall, just right to set on a workbench. It's a 25lb. upright strap hammer and seems to be more than 100 years old. It's serial #231. Has the early tensioner. Think these were made to go 450 or so blows per minute! GREAT FUN! grant

GRANT -- NAKEDANVIL at USA.NET Saturday, 05/02/98 04:09:39 GMT


Sounds like a fun toy. Actually a museum piece! Had a guy tell me about a hand operated bench top shaper. Another neat toy for a small shop!

-- guru Saturday, 05/02/98 15:28:57 GMT


It may be in the original edision, but I sure can't find it in the revised edition! Happy digging! (grin)


With all the tools you've got in the shop, you don't need that Bradley. Why don't you send it my way, I can put it to good use! (grin)


Jim Wilson -- pawpaw at Saturday, 05/02/98 18:14:12 GMT

Syeeb,Syeeb,Great Syeeb,Honorable of all Garues,
It just rained here at Tent City and the dust is settling. The wife is cooking tradition cuisine and the children are outside playing sand games. As for myself I am doing fine and there is no cause to be alarmed; thanks for being concerned. I have been busy lately planning my backyard black-smithing area. I decided to use aluminum close boarded fencing in a 20' x 16' area connected to my shed,as my smithing area.I spoke to my neighbors and we came up with a suitable style of fence we both liked.I have great neighbors,like my Garu,same thing but different!
I will be happy to post the stages of completion of the homemade metal cutting bandsaw I am soon to start building.With my gas and arc welding equipment and the free use of my buddy's machine shop I hope I can complete it as accurately as possible.It looks Like I have gotten long winded again;something I do often.I can see in the distance a caravan,I recognize as being of a friendly kind.Looks like company again.Iwill have to start filling drinking buckets for the camels,they will have a real thirst to rectify!!!!!!Stay well,live long and prosper.


TH BUB -- hagiumet at Saturday, 05/02/98 19:25:43 GMT

Jim: (Bealer and the brown paper)

I think you have caught the Guru in a faux pax! I couldn't find it either and I've been giving Bealer credit for years. It probably came from Eric Sloane, but I quickly scanned A Museum of Early American Tools and didn't see it. However he was one for putting little tid bits in intresting places. I've got six more of his books to search as time allows. . .

-- guru Saturday, 05/02/98 20:04:11 GMT

"I think you have caught the Guru in a Fax Pax!"

I can't believe it!!!!!!!!!!!!!

My day is MADE!! (very large grin!)


Jim Wilson -- pawpaw at Saturday, 05/02/98 22:42:36 GMT

And here I always thought it was "Fo Paw" as opposed to "Hind Paw"!

go figure. I guess this conversational stuff post to be in da pub!


grant -- NAKEDANVILFIRE at USA.NET Sunday, 05/03/98 04:19:01 GMT


Actually, it's "Fo Paw Paw". That's the address you need to put on the Bradley, before you ship it out! (grin)

Jim Wilson -- pawpaw at Sunday, 05/03/98 11:12:35 GMT

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