Wednesday, October 12, 2011

Using Vise Mounted Bending Forks

22 June 2010

There are many good ways to bend curves in steel and iron. Many blacksmiths bend curves over the horn of the anvil, whether the curve is ½ inch in diameter, or five feet in diameter. When striking hot steel over the horn of the anvil, one by necessity has to leave hammer marks on the steel, simply because you are hitting hot soft material with a hardened surface of a hammer. Hammering a piece of steel mounted fast on a bending jig has the same problem, hitting hot material with a hard surface leaves impressions on the forging.

A nice alternative, easy to make, is a vice mounted bending fork. Because the blacksmith holds the bar of steel in tongs when bending hot steel between the tines of the fork, the torque increases towards bending the hot steel simply because of the length of the pair of tongs. This allows the smith to exert great force on the object he is bending, without leaving hammer marks.

Let me use this example of forging a chain link out of 5/8 inch round mild steel. To make the bending fork, simply take a piece of 5/8” round, which is commensurate with the size of the stock being used for the chain link, and bend it into a U-shape. Make absolute sure that when you bend the bar into the U-shape, the tines are about ¾” apart. The reason for this small gap between the tines is control of the hot bend. Please see figure 1.
Figure 1
Bending Fork

This fork is then mounted and tightened in a blacksmith vice as in figure two. The tines of the bending fork should extend.upwards from the vice jaw about two inches or so. See figure 2.
Figure 2
Bending Fork Locked in Vice

To bend oval links out of 5/8” steel, I cut 14 inch lengths of that material. I heat up one end of the bar to a yellow heat, then bend one end between the tines of the vice mounted bending forks. By making the bending forks tight with the tines close, I can either bend wide or sharp tight bends between the forks, bending the bar in increments as I see fit, which gives me excellent control of the radius of the bend. The crosshatched shaded areas are yellow-hot in my diagrams. By holding the cool end in long tongs, I can exert tremendous force on the bend because of the length of the tongs on which I am pulling, Of course, to decrease the need to flatten the work being bend, hold the work as horizontal as you can! Please see the series of figures 3a, 3b, 3c, and 3d.

Figure 3a
Starting the Bend

Figure 3b
Continuing the Bend Further, on the Same Heat
Figure 3c
Still Further on the Same Heat

Figure 3d
One End of Link Finished

Once that end of the link is bent, heat up the other end to a yellow heat, then bend in a similar manner that end between the tines of the fork while hot. After a bit of practice, the bends at both ends of the link should be symmetrical, unless you are bending pear shaped links in which the radii of the two ends of the link are different. Either way, by having the tines close together, the blacksmith can bend any radius he wants between these forks. Figure 4 shows the second side of the incipient link being heated to a yellow heat, while figure 5 shows the finished link. If this finished link does not end up laying flat, simply heat up the whole link to an orange heat, then place it on a steel table and place a large steel plate on top of it, and whack the plate atop the link with a 20 pound sledgehammer to make it lay flat. This is preferable to flattening the link with a hammer on top of your anvil, which will leave unnecessary hammer marks

Figure 4
Opposite End of Link Being Heated

Figure 5
Finished Oval Link

One more thing…….I have seen a lot of blacksmiths try to use bending forks which are mounted in a hardy hole. I believe my vice mounted bending forks are superior to these because most hardy-hole mounted forks have play inside the hardy hole, which causes the smith trying to bend steel to lose torque through play in the tool. Even if there is no slack in the hardy hole, torquing a bend between tines can cause the whole anvil to move, which again causes a loss of torque. My simple forks preclude wobble and play, because the forks are LOCKED in the vice. Also, because my tines are close together, different from most hardy-hole forks, the blacksmith has far better control of the radius being bent between the forks. See figure 6.

My link

Figure 6
Anvil Mounted Bending Forks

Final notes: I have two more notes regarding the use of these forks. Firstly, the size of the material being bent between these forks should be commensurate with the size of the material used in making these forks. It wouldn’t work to try to bend three inch round between a fork made out of half-inch round. Secondly, remember that you are bending hot steel between the tines. Failure to realize this could result in the blacksmith burning his/her elbows on an apparently cold bending fork. With these forks, a blacksmith should be able to bend just about anything with enough practice, from chain links to scrolls, from shackles to basketball rims. Happy Forging!

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