Fixing a warp without Forging experience?

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 ?
 

John Wilson

Well-Known Member
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.
 

Mark Barone

Well-Known Member
Need more (all) of the details. Flavor, thickness, HT, etc.
1/8 thick 1095 , not heat treated
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.
[/QUOTE

i do have a torch and a vice. I’ll try that tonight. It’s not heat treated . Thanks John
 

tkroenlein

Well-Known Member
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.
 

Mark Barone

Well-Known Member
Are you familiar with the 3 pin method of straightening in your vise?
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.
 

opaul

Well-Known Member
Just a question- are you removing the mill scale before you grind or are you purchasing milled flat steel?
 

billyO

Well-Known Member
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.
 

opaul

Well-Known Member
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.
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.
 

Kevin R. Cashen

Super Moderator
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.
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.
 

KenH

Well-Known Member
As you said - do it in the second tempering cycle.
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.
 

opaul

Well-Known Member
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.
 
Top