Straightening a warped blade

Matthew Gregory

Matthew Gregory

Chief Executive in charge of Entertainment
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Jan 12, 2005
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Hey gang,
I just quenched my first 'single-bevel' blade (a la the old Timberline Specwar) and the pig curled right up on me... the obvious assumption I'm making is that there was LOTS of mass on one side and mostly none on the other, and it did the old samurai blade curve, only from side to side rather than up and down.

How the heck do I straighten this pig? The knife was not forged, I did it all via stock removal out of a 2" x 1/8" piece of 1095 that was hot rolled, P&O annealed. Think I should have normalized it before quench anyway? Would that have helped? I just can't feature having brought it up to a temperature where it would have required normalizing...
 
You could re-heat treat and bend it bach or just heat it to tempering temp and bend it back.At tempering temps you'll be amazed how well the steel bends.
 
Matt,
You most definitely should have normalized it. You are still building stresses up in the steel when you are grinding. I would do it a few times. try it again.:D
Mace
 
All right, I'll normalize it for a few cycles -BUT- how about heating to critical, quenching, and immediately after quenching clamp it between two blocks of steel in the ole' bench vise for a bit -- THEN on to tempering?

I tried bending it back to straight during tempering, btw... no dice.

I HT'd three other blades with this one (all the others flat ground with conventional 'V'), and they are all fine. I just can't see that normalizing will answer this. I'm convinced it's due to differences in thermal mass -- BUT I'll try it anyway, just cuz I love ya, Mace. :barf: :D

How's your thumb? Seems like an awfully early time to be making excuses for THE ASHOKAN INVITATIONAL WORLD THUMBWRESTLING CHAMPIONSHIP , which of course by forfeit I hold the title to this year, but I guess preparation is good. No one can accuse you of procrastination, that's for sure!:D
 
You should anneal then straighten it then do the HT all over again. I wouldn't try to straighten it after quenching as it will probably break. It's going to be hard and brittle immediately after quenching.
 
MrPurple said:
How's your thumb? Seems like an awfully early time to be making excuses for THE ASHOKAN INVITATIONAL WORLD THUMBWRESTLING CHAMPIONSHIP , which of course by forfeit I hold the title to this year, but I guess preparation is good. No one can accuse you of procrastination, that's for sure!:D
Click to expand...

Thumb turned out great :thumbup: Up to 85-90% of what it was. In another month or so other than the scar people won't even know I'm a dumb-ass :D
 
Re-anneal it and straighten it. Once straight,normalize several times. Harden with a straight in point first quench.Wear a pair of heavy welding gloves,because you are going to be handling the blade hot right after quench.With 1095 the nose is real fast,so don't waste any time from oven/forge to quench tank (make sure there is enough quenchant,too at least 1-2 gallons of fast oil). Also,make sure you soak the blade at the right temperature (don't overheat it) for at least 2 minutes on an 1/8' blade. After about ten seconds in the quench tank,pull it out and look at it .If there is a warp,straighten it right away .You have only about a 20 second straightening window before the blade starts to get brittle.During that 20 seconds the blade is very bendable. A few taps on the anvil (or on a piece of oak) will do a small warp. A bigger warp/twist is best done by sticking one end in the vise and twisting/bending with a pair of drawing pliers.Do it while the blade is still quite hot. Don't be too slow or too gentle,or the blade will cool off before you get the bend out - and the blade will break.. Once it drops to 200 don't do anything or it will snap. Remember that the vise will suck the heat from the blade real fast,so don't put it in the vise until you are already holding the blade with the pliers.Tweak it quickly, remove it from the vise,check that it is OK and stick in a 400 degree oven.By having a hot oven (toaster oven works fine) right there,you can keep the blade from cooling below Mf. Until that point,around 200, the blade is quite bendable. Once it crosses the Mf point,it will break.
When quenching I hold the blade with a pair of wide nose tongs. I pull it out,sight down the blade,stick it in the caulking vise and step on the pedal to close the jaws, twist/bend,pull out,do one more quick bend,and stick into the temper oven. If I have to do more straightening,I wait about 5 minutes to make sure the blade is fully 400 degrees.
If you don't have a good vise at the quenching area,use two good heavy pliers. Drawing pliers or sheet metal pliers have flat wide jaws,and are excellent for this task. Cheapos from HF will be fine.You can even pre-warm the plier jaws before the HT so they don't cool the blade any more than necessary.
Stacy
 
Arthur Washburn said:
Thumb turned out great :thumbup: Up to 85-90% of what it was. In another month or so other than the scar people won't even know I'm a dumb-ass :D
Click to expand...


Hey Arthur! I totally forgot that your thumb was messed up too... that message was aimed at Mace! He's been dodging me since before the Ashokan get-together, as he's embarrassed at how badly I'll beat him (all 153 pounds of me).

Either way, it's good to hear you're on the mend!

Stacy, I've started the annealing process... so much for getting this done tonight, eh?
 
Man, that's hard, bro.

Is the general consensus that it should have been normalized prior to heat treat? I was under the assumption that stress buildup of the kind that normalization fixes (- aside from reducing grain size) was for stresses applied at or above A3?
I plan on making a number of knives in this style, so I'd prefer avoiding this problem next time!
 
Best to normalize all metal that has been modified in any way (forging,grinding, bending) . I hardly ever have any warp beyond a tiny curve since I started doing it.
 
One trick I have had good success with is to put the point area in the vise, heat the spine in the area of the warp to a broze color, over flex the warp out of it, then pour water on it. It often takes more than one attempt, but works well on 1095, 01, file steel.
 
MrPurple said:
Man, that's hard, bro.

Is the general consensus that it should have been normalized prior to heat treat? I was under the assumption that stress buildup of the kind that normalization fixes (- aside from reducing grain size) was for stresses applied at or above A3?
I plan on making a number of knives in this style, so I'd prefer avoiding this problem next time!
Click to expand...

Well, you have to consider that stresses are imparted to the steel as it's hot rolled at the mill. The reason it was straight when you got it is likely due to the fact that there was enough mass to hold the stresses in check. Once ground and shaped, you've unbalanced the existing stress in the steel and so normalizing is a good idea.

That's my take on it anyways. You can keep the change from the $.02 :)

-d
 
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