10 replies to this topic

[Ben Christy]

I have been trying to forge a pair of bolt head tongs using the champion method as described by Bill Epps and I have a problem. Every time I form the shoulders for the boss where the rivet goes cracks begin to appear in the radius of the shoulder. As I continue to draw out the jaw the cracks get worse, to the point it looks like the metal is crumbling almost like the crumb of bread. I have tried changing my materials around to no avail. My other thought was that the metal was bending at the shoulder while bellow the forging temperature of the metal because it is thin there. Yesterday I was very careful about both forging temperature and keeping the shoulder/boss from bending and I had the same problem. I am at a complete loss I have tried 6 times now to make on and each time the same thing happens. I will admit I took about a year off from blacksmithing and Im just getting back into it so maybe there is something I am forgetting?

[Wesley Chambers]

Its been my experience that most times when your getting fractures its a heat issue, your shocking the metal out of its plastic zone, you did say you were checking your forging temps, but what material are you actually using?

[Ben Christy]

I first started out wit plain hot rolled 1/2 round mild steel. The last two times I attempted with railroad spikes as I felt the the 1/2 was to small for the tongs.

[brianbrazealblacksmith]

It sounds like you are doing what most people, including myself, have done when first trying to make tongs. That is, forging the shoulder down too far before you have developed the other parts of your tongs. If you do this and you still have more work to do in other areas, the material will always bend at the weakest point and will develop stress fractures which can eventually break.

[Ben Christy]

brianbrazealblacksmith, on 29 August 2010 - 12:56 PM, said:

It sounds like you are doing what most people, including myself, have done when first trying to make tongs. That is, forging the shoulder down too far before you have developed the other parts of your tongs. If you do this and you still have more work to do in other areas, the material will always bend at the weakest point and will develop stress fractures which can eventually break.

Should I wait to do the shoulder last then. OR just get it started and move on and finish it up last?

[Nakedanvil - Grant Sarver]

As Brian noted, until you develop more control, you'll end up bending a weak area back and forth. Another thought: are you working over a nice radius corner on your anvil? A sharp corner can start many cracks too. I run into that doing something on someone elses anvil that has a sharp corner where I expect a radius.

[forgemaster]

I'll side with Grant on this one, radius, radii, radiuses, when necking. When I tryed making my first pair of tongs in the back shed at home as a teenager, I used a hardie to neck in at the ends of my eyes, then as I bashed and crashed out the reins and the jaw I had a crack start and like you have had, run right across to the other side, then break off in my hot little hands (vise grips). It was'nt till I started my apprenticeship that the need for radii was fully explained to me.

Phil

[Frank Turley]

You're probably working too cold. In the British book, "The Blacksmith's Craft", all three shoulders of a flat jawed tong are done at a light welding heat.

http://www.turleyforge.com Granddaddy of Blacksmith Schools

[fciron]

If you combine the two suggestion here you will get one of my errors: a sharp corner in the shoulder and working too cold so that the shoulder is at a black heat. There is a range of temperature, I think it's about 800-900 F, just after the metal stops glowing, where steel is actually more brittle than it is at room temperature.

In addition to a nice radius inside the shoulder, I would try too keep the eye area at an incandescent heat while forging. Whenever I am working a piece with this sort of weak point/stress riser (like a big leaf on a narrow stem) I try to keep the weak point at a glowing temperature so that any force put on it will cause plastic deformation rather than simply flexing it, which can give rise to cracks.

I also discourage unnecessary quenching. This can also aggravate stress areas, even in mild steel.

Lewis

[brianbrazealblacksmith]

Also, forging squarely, as opposed to out of square and creating a rhombus or parallelogram, will help gererate more heat to be able to forge longer and create a stronger structure.

[yesteryearforge]

I like it when ya'll use big words

Mike