Easiest ways to straighten steel

[bodog]

Another thread had several guys wanting to know the easiest ways to straighten curved steel bars. The thread went a little downhill so I'm opening this for guys to ask for and receive help. Thanks.

 

[Tom Lewis]

For forging it doesn't matter, for stock removal it does. What I do if I am going to do stock removal is to cut the steel to lengths and grind out the profile. Then I put the knife blank on a flat surface like a table saw and check for flatness. If it is not flat, I place the blank on a block of steel with the curve up, and hit the blank with a rawhide mallet. The rawhide mallet will not dent the steel.
If the blade is twisted I put one end in a vice and use a wrench to straighten.
It's really not that hard to straighten the steel. But, I had much rather start with straight steel. When I buy CPM 154cm steel, I buy several pieces at a time and give instructions to pack the steel really good so the shipper won't have a chance to bend it.

 

[Stacy E. Apelt - Bladesmith]

I like to place the bar on a wood plank, curved side up. Shim it with a piece of wood/steel that is a bit more than the amount of warp. Work your way down the bar with a dead blow maul or big mallet. It needs to flex about as far past center as it is warped for the warp to be removed. If it is resisting, use a thicker shim. In many cases, I just put a foot on the bar and push down.

Another good method is a straightening/bending fork. Take a 5" piece of square stock the size of your hardy hole. Weld two 5" pieces of 3/4" round stock on opposing sides to make a 3" tall fork. The 2" overlap where the weld is leaves a 3" stub for the hardy. Drop it in the hardy and put the warped bar between the forks. Work your way down the bar and slowly relieve the warp. The same tool is used to make curves, loops, and swirls in blacksmith projects ....or to un-do them. No forger should be without one of these and a hot cut hardy tool.

Another tool is a similar device made by cutting a 3" deep slot about 1/2" wide in the end of a 4X4. A chain saw does this quite well. Either clamp the board in a big vise, or even better, bolt it to the end of a workbench. Use it as above for straightening.

 

[Ja Baudin]

When you say curve side up, do you mean convex side up or concave side up. Just need a little clarification.

Thanks

 

[Stacy E. Apelt - Bladesmith]

The warp facing up - convex up. You need to un-bend it about as much past straight as the bend currently is. If the warp is 1/4" high at the center of the bar, bend it 1/4" past starlight. That is what the 1/4" shims on the ends do.

If you have a big enough oven for the bar, after straightening, place it in the oven at 1250F for six to twelve hours. This will stress relieve it fully. Re-straighten if needed after that.