Straightening a warped blade...

Jericoh

Well-Known Member
Seriously, I'm about to wig right out. I have a piece of 3/8" 1095, ground out and then I heat treated it. It warped. A nice gentle curve from tip to skullcrusher. So I tried the trick posted here and clamped it to another piece of 3/8" steel, with a penny at the apex of the curve, it was straight in the clamps, and then tempered it. Took the clamps off and poof, still curvy. So I annealed it and then did the clamp trick again, still a boomerang.

So then I heated it up to about 1300 degrees, put it in the vise with a flat wrench at the apex and 2 flat wrenches on the other side as far forward and aft as I could space them, cranked the thing down until it was curved the other direction. Let it cool, unvised it, and bang, curved right back to the other side.

I'm seriously considering propping the thing up with a couple scraps of steel at the tip and the skullcrusher and parking the tire of my Expedition on it. Anyone else have any other ideas before I find my car keys?
 
Frustrating, ain't it.
I had 2 knives from the same 1/4" bar do the same thing regardless of all the tricks used. I finally annealed them and beat the living daylights out of the blades with my wooden mallet.... after the first normalizing heat, beat them again with the mallet ....continued with 2 more normalizing heats...hardened and tempered. I think the mallet work at heat helped beat the memory out of them. Also the warping may have come from the quenchant temp being to low (?) or improper dunking procedure. (side to side). If you don't have an anvil, open the jaws on your bench vise a couple inches or so and work the blade with a block of 2x4 after heating the blade. Good luck.

Rudy
 
Sound like Rudy's the man with the plan here. Sometimes all you can do is to go back and repeat the normalization 2-3 times, make sure that it's straight before and after pre-hardening austinization and then requench. From what you've said that you've done, I'd say that you're just about at that point. One danger in pushing cold straightening too hard is that you may well end up with a broken blade. I know, believe me I know.

Doug
 
Thanks guys. I took a coffee break and don't feel like bashing myself in the head with a bar of steel. I re-heated it and have it all clamped in the vice again. One thought though, when I heat it do I need to get it to 1475 like I would for treating, or is 1200-1300 fine? I'm gonna let it sit and cool, then unclamp it and see what happens. If I don't check back in I beat myself to death with the boomerang.
 
Jericho,

The first normalizing heat before bashing it with the mallet was at nonmagnetic, which would be just a bit lower than 1475. I'm using my forge until final HT. In my mind, the closer to quench heat...the better. Don't give up and learn from it.

Rudy
 
I'm on the hunt for a good sized brick right now. Goodbye cruel world. Is there a limit to how many times a piece of metal can be heated and messed with? Gonna take it to 1475 and try again.
 
I make little bitty folder blades so this may not work for you,but I straighten my blades within a few minutes after quenching,they are so easy to bend it's unbelievable. I can't remember where I first read about this but when I tried it, it worked. I swear it's easier to bend the steel at this time than it is before I heat treat it and I'm not the least bit afraid of breaking the blade,this method has taken a lot of stress out of my life. I use mostly D-2,and Sandvik stainless but it also worked on a piece of Mike Norris stainless Damascus I just used and it also works on Alabama Damascus . My blades are relatively short and stout so I us an arbor press to do this with, these little folder blades have to be perfectly straight or they won't look right. Try this, it just might work for you, I hope it does.
 
Steel can be stubborn. To prevail you must be more stubborn. Try a hand sledge a piece of clear pine or soft plywood (not fir) and a ~1.5"x1.5"x6" piece of oak.

1. Put the plywood block on a solid concrete floor

2. Center the blade on the block with the convex side up

3. Center oak over center of bend covering ~1.5 square inch of the blade

4. Strike oak "punch" hard with a hand sledge

Note: This "process" is derived from the principle: "When all else fails, get a bigger hammer."
 
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3/8" is pretty thick...

You might try over bending in the clamps when tempering, and when you temper, you might need to let it soak for a good 2 hours or so. Some times it take a couple tries. Be patient. That's a lot of steel to heat through.

Granted, now it sounds like you need to completely re-heat treat and temper again anyhow.

BTW... are you using an oven? Forge? What? Are you heating the blade evenly?
 
It's in an Even Heat oven. Just took it out, yet again and have it all clamped up. It is insanely curved to the other side this time. Using 2 wrenches, one at the tip and one on the skullcrusher, on one side and another wrench pushing on the apex on the other side. I found one problem in all this, i was using a piece of 1/4" stock to clamp the blade to and the blade was actually bending the 1/4" so I wasn't getting a good bend in the opposite direction. Then I went to a piece of 3/8" to clamp it to, now I have 2 pieces of 3/8" stock that it's clamped to.
'"
 
Woot, it's finally straight. Now I have to harden it again and watch, it'll probably go back to boomerang....
 
If it goes back again, just repeat what you just did through a couple of temper cycles. You'll get there. You definitely need to clamp against something that won't flex though. Square tubing is also an option.
 
Channel iron is rigid. You must use something that is more rigid that what you are trying to bend - 1/4" gauge angle iron is also pretty rigid. This walled 1/4" square tube (as mentioned above) will also prevail over your 3/8" stock.

Don't give up, you will eventually win.
 
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Yeah, I tried 1/4" thick C-channel and 1/4" bar stock. Next I going to pick up some square tubing.
 
3/8" is pretty thick...

You might try over bending in the clamps when tempering, and when you temper, you might need to let it soak for a good 2 hours or so. Some times it take a couple tries. Be patient. That's a lot of steel to heat through.

Granted, now it sounds like you need to completely re-heat treat and temper again anyhow.

BTW... are you using an oven? Forge? What? Are you heating the blade evenly?

This works for me to. :)

Seved
 
A SIMPLE WAY. After tempering, try and determine the main offending area. Cleanup at least one side of the blade to show heat color, vise the tang, heat the area at the spine to maybe blue being careful to not allow color to go to the edge. Over flex the blade a tad beyond straight, hold there and pour water on it until it is cool. Repeat if needed. This is how Bill Moran did it, and it works.
 
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