Fixing a warp without Forging experience?

Mark Barone

Mark Barone

Well-Known Member
The 12 inch knife I am making as a slight bow in it. Lying flat there is probably a 1/16 maybe am 1/8 inch space under the center when placed on a flat service , my table saw. I have a kiln , I have a vice, I don’t have an anvil. I have a sledge. I would like to get it flat before
I start the bevel. Any suggestions ?
 
If the steel hasn’t been heat treated yet, just chuck it up in a vise and tug on it. Use a straight edge to check your progress.

If it’s been heat treated and tempered you can gently heat the spine with a propane torch and give it some persuasion in the vise just like above.

If the bow is not too much, grind it out. Mark your centerline with the blade on a flat surface and grind to the line.
 
tkroenlein said:
Need more (all) of the details. Flavor, thickness, HT, etc.
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1/8 thick 1095 , not heat treated
John Wilson said:
If the steel hasn’t been heat treated yet, just chuck it up in a vise and tug on it. Use a straight edge to check your progress.

If it’s been heat treated and tempered you can gently heat the spine with a propane torch and give it some persuasion in the vise just like above.

If the bow is not too much, grind it out. Mark your centerline with the blade on a flat surface and grind to the line.
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i do have a torch and a vice. I’ll try that tonight. It’s not heat treated . Thanks John
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Yup just straighten it. Though I would HT before grinding at all because it's much easier to straighten a profiled blank after HT than it is a ground blade. I'm not living well enough to ever get a 12" knife HT'ed without needing straightened.
 
Chris Railey said:
Are you familiar with the 3 pin method of straightening in your vise?
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no I don’t. I tried looking it up on you tube. I actually straightened it out pretty good. With theeception of the last 1 inch. i can’t seem to get it bent in the vise. It’s very minor. So I am interested in the pin method.
 
Just a question- are you removing the mill scale before you grind or are you purchasing milled flat steel?
 
I'd say keep working at it until it's straight if you haven't quenched it yet. How I deal with warps after quenching is to immediately do one tempering cycle, then I use 2 pieces of angle iron, 3 small c-clamps and as many dimes as needed to shim the blade where needed to slightly over-correct any bends while clamping the blade between the pieces of angle iron. I check for straightness after each temper cycle and repeat until straight.
I always do 2 temper cycles on my blades even when completely straight, and have had to do as many as 6.
I hope that makes sense, if not I can get a picture.
 
billyO said:
I'd say keep working at it until it's straight if you haven't quenched it yet. How I deal with warps after quenching is to immediately do one tempering cycle, then I use 2 pieces of angle iron, 3 small c-clamps and as many dimes as needed to shim the blade where needed to slightly over-correct any bends while clamping the blade between the pieces of angle iron. I check for straightness after each temper cycle and repeat until straight.
I always do 2 temper cycles on my blades even when completely straight, and have had to do as many as 6.
I hope that makes sense, if not I can get a picture.
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I’ve used the tempering technique on a slightly warped blade out of quenching and it has worked well. As you said - do it in the second tempering cycle.
 
billyO said:
I'd say keep working at it until it's straight if you haven't quenched it yet. How I deal with warps after quenching is to immediately do one tempering cycle, then I use 2 pieces of angle iron, 3 small c-clamps and as many dimes as needed to shim the blade where needed to slightly over-correct any bends while clamping the blade between the pieces of angle iron. I check for straightness after each temper cycle and repeat until straight.
I always do 2 temper cycles on my blades even when completely straight, and have had to do as many as 6.
I hope that makes sense, if not I can get a picture.
Click to expand...

Oh yes, this reminded of one other good point. With knives I never really had to learn this lesson, but swords taught me one important thing about straightening unhardened blades cold. Never forget the cause- unwanted strain energy. Anytime I move metal cold, I stress relieve before proceeding. If it takes a set again, the stress relieving, or normalizing, hasn't done the job yet and keep going until it does. Flexing the steel isn't a problem, but if the strain I induce results in a permanent deformation- there IS stored strain energy, that will become an introduced variable later on. At the end of forging- normalize if it is straight when it cools, it worked, if it isn't- it hasn't taken yet.
 
opaul said:
As you said - do it in the second tempering cycle.
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That's a new one for me - I've always did my straightening from 1st tempering. Not 3 pin method for first, just clamp between two flat bars and hope that does it with first tempering. If not, then 2nd tempering cycle I'll use the 3 pin method.

I've always been concerned about how brittle a blade is direct from quench to try 3 pin on first temper.
 
It doesn’t take much of a flex to break a freshly cooled quenched blade that’s why I do it on the second temper. I use a flat bar with clamps and spaces to counter the warp similar to the method as described by BillyO.
I haven’t used the three pin method as I stated in my post.
I guess we all use the method that works best for the individual.
 
John Wilson said:
If the steel hasn’t been heat treated yet, just chuck it up in a vise and tug on it. Use a straight edge to check your progress.

If it’s been heat treated and tempered you can gently heat the spine with a propane torch and give it some persuasion in the vise just like above.

If the bow is not too much, grind it out. Mark your centerline with the blade on a flat surface and grind to the line.
Click to expand...
I second the torch method. It's a lot easier than it looks. If nervous about tempering the edge hold a wet towel on the edge when you heat and bend. Don't burn yourself lol
 
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