Straighten During The Temper

It all starts with our selection of steel, that is the foundation of a high endurance performance blade, from that point on it is either that we control the steel or it controls us.
 
Thanks a lot guys...


After mooching so many tips and tricks from the great makers here, I'm glad I found something (even though many have used it before me) to contribute back into the pot! At my former job we used to do this with steel plates up to 8"x 96" x 200" in ovens that you could drive a tractor trailer into. That's over 19 tons of warped steel!!!

annealling.jpg
 
Rick Marchand said:
Thanks a lot guys...


After mooching so many tips and tricks from the great makers here, I'm glad I found something (even though many have used it before me) to contribute back into the pot! At my former job we used to do this with steel plates up to 8"x 96" x 200" in ovens that you could drive a tractor trailer into. That's over 19 tons of warped steel!!!

annealling.jpg
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That must have taken a HUGE amount of pocket change for shims....


Tried this last night with some 1/8" 1084 - started with 3 blades and 2 warped during quench. Worked like a charm on both. Shim equal over, temper, let cool and release from clamps. Straight as an arrow now.

Thanks Rick.
 
Rick: I tried your method last night on an 8" long chef's knife made from 3/32" 1095. I don't forge. I only do stock removal from plate steel. The blade was only slightly warped (say about 3/32"). I modified your method a bit in that I clamped the blade between two big files. I tempered it twice at 400 and 425 for two hours each time. I still had some slight bit of warp in the blade. Not enough that I could actually see but enough to be disclosed on a very flat surface. I think that I will try the one file method using one file and some very thin shims. Any comments? Thank you very much for this very useful tool. I am in your debt. Nicholas Jasper.
 
Nicholas... the only suggestion I would make is to check it after each temper in the future. You oftentimes need to shim a bit. Clamp it straight the first time. If it doesn't come out true, shim it the second time. Alway start straight, though. There have been times when I thought that i needed to shim past straight to correct a warp, only to find that it locked in the over-bend.... doh. Sometimes, it's like watching tennis until you nail the process.

Rick
 
Did I ever tell you I love you Rick? :eek: In a manly fashion of course! :p;)

Tried it and it worked perfectly. (Well not perfectly but the slight warp left is due to me learning how much to shim the blade, I think I got it now). Did a blade (1095) first at 400F then 425F. Behind me are the stressful days of straightening in the vise.:thumbup:

Thanks again for sharing!
 
After all manner of trying to straighten blade, often as not breaking them, I tried your method and it worked great. So simple too, thanks Todd
 
Mr. Fowler kinda hinted at something there that probably shouldn't be overlooked. If the steel is warping in the quench, there could be a little more going on and straightening it might be kinda like putting on a bandaid over a splinter. Uneven forging, uneven grinding, etc... There is a reason.

That said, I've straightened many blades after the quench but I don't like to do it. In addition to a few things I've learned from Mr. Fowler, try some advice Howard Clark gave me and I think it is okay to share here: (paraphrasing from my memory) after a few regular normalizing cycles, do a 1400 deg normalization. Straighten the blade. Do another 1400 deg normalization. Straighten. Do it over and over until the blade stops moving. It usually stays pretty straight after the quench with this little drill. This helps (with my sword blades) greatly. Especially with my damascus.
-M
 
Michael Rader said:
Mr. Fowler kinda hinted at something there that probably shouldn't be overlooked. If the steel is warping in the quench, there could be a little more going on and straightening it might be kinda like putting on a bandaid over a splinter. Uneven forging, uneven grinding, etc... There is a reason.

That said, I've straightened many blades after the quench but I don't like to do it. In addition to a few things I've learned from Mr. Fowler, try some advice Howard Clark gave me and I think it is okay to share here: (paraphrasing from my memory) after a few regular normalizing cycles, do a 1400 deg normalization. Straighten the blade. Do another 1400 deg normalization. Straighten. Do it over and over until the blade stops moving. It usually stays pretty straight after the quench with this little drill. This helps (with my sword blades) greatly. Especially with my damascus.
-M
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I agree... if my blades are ending up warped after the noramization, something is wrong and I deal with it before I go any further.

My first paragraph in this thread "hinted" to that as well. I really didn't think it needed to be stressed as it is just common sense to do everything you can to prevent warpage from the get-go. To most of us, Ed was just stating the obvious.

I had taken some pics today with intent to post a thread on how I straighten during the temper. I found it interesting that just before dinner, I received an email from a member asking about straightening.... coincidence? (I find that happens a lot on these forums.) Whenever I'm having a problem, someone usually is posting about the very same issue. I'd like to start by saying that proper normalization and pre heat treat practices would eliminate most of your warping issues. Tweaking during an interupted quench is very handy as well. Most of the makers I see use straightening jigs after the temper and over-bend enough for the blade to take a set. I'd like to tell you that my heat treat is so good that even the most exagerated bends spring back to shape... but I'm afraid that isn't so. Some blades work out well in a straightening jig and some snap. I have also clamped the tang in a vice and used a slotted 2x4 to bend and twist the blade back to true. The sad fact is that "warp happens" and our goal is to true the blade while keeping it in one piece. That is why I felt compelled to get this thread up, as I think it could prevent some broken/scrapped blades.
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I believe it is unreasonable to think that even the most experienced knifemaker can completely eliminate warpage with pre-heat treat practices. Steel is what it is.

This thread was addressing that. It is a band-aid. We need band-aids to fix symptoms. It is a continual battle to cure the problem. These techniques simply limit the number of casualties in the war.

I hope that I didn't come off as rude... that was not my intent. Everytime this thread surfaces, people message me telling me that this doesn't fix the problem... Yes, I am aware of that. You wouldn't treat the symptoms of food poisoning by reciting proper food handling practices.

Thanks
Rick
 
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No problem. It's an ongoing battle and I've struggled with this more than most, as I deal with swords and with very thin Chef knives almost exclusively. I really, really try to eliminate the need to straighten and that is what I wanted to emphasize here. I use the three-pin press for swords and clamp-plates for my kitchen knives all the time, but I don't like it, and I feel as if I might have lost quality along the way when I have to do it. Just sayin...

Have fun. Keep at it.
-M
 
Thanks, Michael... I'm glad my post didn't offend (it went the way of a rant for a bit). I'm interested as to why you think there could be quality loss in the straightening process?
 
I'm not talking so much about a "quality loss" in the final product but that I was sloppy in my forging or grinding to cause the warping in the first place. Think about it: you quench a blade and it comes out bent to one side. That was caused by "something" and now the blade is in the state it wants to be in. Next you bend it to a state where, in your mind, it is straight and perfect, but now it is under stress and that is why I made the comment about the band aid over the splinter. We all do it and I've straightened more blades than many of you ever will in your lifetime, but I "feel" that my best work occurs when my blades come out perfectly straight. Then I know the "quality" of my forging and grinding were right on.... IMHO :-)
-M
 
That makes sense, Michael. I have to wonder if using the clamp/temper method induces stress or relieves it. You are obviously putting strain on the blade in the clamped postion but once the tempering cycle is done the unclamped blade holds it's shape. I rarely have to over-bend the piece to get it true.

Thanks again for sharing your experience.

Rick
 
I learned my lesson many years ago: I ground a fancy knife blade out of a file, finished it up with a WWI trench knife handle. The knife hung on my kitchen wall for years, then one day it snapped, all by itself hanging on the wall it broke at mid point, the front half of the blade fell on the floor. Evidently my grinding methods obviously left stress in the blade that eventually caused the blade failure. This event remains prominent in my mind.

I believe blade warp is caused by stress in the blade, when you straighten the blade you promote additional stress that can lead to blade failure.

I do state that we have learned how to eliminate blade warp in the blades we forge with the steel we use, high quality 52100 and 5160. We have not had a blade warp in our shop for over 8 years, this includes students blades of many lengths and dimensions.

I do not try to make any claims for those of you who do stock removal, your challenges are yours to meet.
 
Ed Fowler said:
I learned my lesson many years ago: I ground a fancy knife blade out of a file, finished it up with a WWI trench knife handle. The knife hung on my kitchen wall for years, then one day it snapped, all by itself hanging on the wall it broke at mid point, the front half of the blade fell on the floor. Evidently my grinding methods obviously left stress in the blade that eventually caused the blade failure. This event remains prominent in my mind.
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How was that blade ground any differently from any other? I don't think it's obvious that your grinding caused the failure, especially years later. There could have been something wrong in the file before you ever bought it that would have caused its failure if you had just left on the workbench in the shop.
 
I just wanted to say that I have used this technique and it has saved my bacon on a few blades. I like Rick 17% more after reading this thread. ;) :)

I agree that trying to avoid it in the first place is the best idea, but sometimes crap happens. I am meticulous about every step and use both a Paragon and digitally controlled salts in my shop with commercial grade quench oils, and there is still the occasional blade that has a wandering tip. I think some days I just don't hold my mouth just right.
 
This is a great tip and I heard it from John White. I haven't needed it often but the couple times I have it's worked splendidly.

That said, this is a great thread with several more tips I will certainly add to the routine. Thanks all.
 
i might hav eto revisit a few blades i have on the shop floor to reHT and then temper and use as house knives (or give to fam) to see what happens to them over a longer term


ed if the blade snapped how can you be sure that it was not from HT as you said it was many years ago since you use a torch i know you have only gotten better at how you read heat color/ temp. What prosess were you using at that time as i know you have changed things a bit in not only what steel source you used but also heating and quenching you do/ cycling
 
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