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Warped knife blade

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Hello all.
I've just started building knives and I'm now working on my second knife. The blade came out of the quench a little warped. I've heat treated it 3 times at 400 degrees with the blade C clamped onto a 3/4 inch steel plate with a shim. Most of the warp came out but there is still a slight warp towards the tip. Is there any other methods which could straighten out the blade? The blade itself is 1084, 5/32 x 1 1/2 x 7.

Thanks for reading.
 
You can continue to re-temper as many times as it takes to unwarp it. At the same temp of course. Re-temper at the same heat will not hurt anything. There is another method, but it carries a risk. Lock in a vise after polishing where you can see colors in the warp area. Heat the spine carefully while bending the blade to over flex a bit at the apex of the curve in the warp. Have a can of water ready to pour on it. When you have the heat at a blue in the warp area at the spine, but before the color reaches the edge, pour on the water while keeping the blade flexed over. This will not work up near a point. You will end up over heating the point area. You can also re-temper as you were with C clamp and wedge, but once you are confident that the heat is soaked through well, quench in water while still clamped. Or just pour plenty of water on it. As mentioned, you can repeat this over and over. Your other option is to regrind the area, if possible, while not over heating it. You may have to settle for less length.
 
The way I do it if I have a blade warp when I quench. I take the blade from the kiln to the quench tank, after a few dunks I sight down the blade if I see a curve I take it too the vice and straighten it while it’s still hot. You have a short window to do this but it works good for me.
When I say still hot, I’m not talking about red hot I mean still to warm to handle without gloves. Before it cools down completely I find the steel to still be workable. If you allow it to cool to far it will snap while bending.
Then test the hardness with a file and temper as normal. Hope that makes sense.

Joe
 
You can continue to re-temper as many times as it takes to unwarp it. At the same temp of course. Re-temper at the same heat will not hurt anything. There is another method, but it carries a risk. Lock in a vise after polishing where you can see colors in the warp area. Heat the spine carefully while bending the blade to over flex a bit at the apex of the curve in the warp. Have a can of water ready to pour on it. When you have the heat at a blue in the warp area at the spine, but before the color reaches the edge, pour on the water while keeping the blade flexed over. This will not work up near a point. You will end up over heating the point area. You can also re-temper as you were with C clamp and wedge, but once you are confident that the heat is soaked through well, quench in water while still clamped. Or just pour plenty of water on it. As mentioned, you can repeat this over and over. Your other option is to regrind the area, if possible, while not over heating it. You may have to settle for less length.
Thanks very much for the advice. Because the warp was so close to the point, I did the re temper method you described and that has solved the problem.
 
The way I do it if I have a blade warp when I quench. I take the blade from the kiln to the quench tank, after a few dunks I sight down the blade if I see a curve I take it too the vice and straighten it while it’s still hot. You have a short window to do this but it works good for me.
When I say still hot, I’m not talking about red hot I mean still to warm to handle without gloves. Before it cools down completely I find the steel to still be workable. If you allow it to cool to far it will snap while bending.
Then test the hardness with a file and temper as normal. Hope that makes sense.

Joe
Thanks, This will help on my next knife.
 
The way I do it if I have a blade warp when I quench. I take the blade from the kiln to the quench tank, after a few dunks I sight down the blade if I see a curve I take it too the vice and straighten it while it’s still hot. You have a short window to do this but it works good for me.
When I say still hot, I’m not talking about red hot I mean still to warm to handle without gloves. Before it cools down completely I find the steel to still be workable. If you allow it to cool to far it will snap while bending.
Then test the hardness with a file and temper as normal. Hope that makes sense.

Joe

I do about the same HAMANKY, using hand pressure, but it was too late for KSWAN unless he wanted to repeat the entire process. It seems his problem is solved now.
As far as window times on hand straightening, it varies with steel types. I used 01 and it would allow as long as 8 to 10 minutes to straighten, but I always tried for 5 minutes or less. The 10XX steels offer the shortest time frames in this practice. With 10XX steels the risk of breaking accelerates rapidly under 400°, while 01 continues to allow some amount of straightening even nearing ambient temp.
 
Last edited by a moderator:
I do about the same HAMANKY, using hand pressure, but it was too late for KSWAN unless he wanted to repeat the entire process. It seems his problem is solved now.
As far as window times on hand straightening, it varies with steel types. I used 01 and it would allow as long as 8 to 10 minutes to straighten, but I always tried for 5 minutes or less. The 10XX steels offer the shortest time frames in this practice. With 10XX steels the risk of breaking accelerates rapidly under 400°, while 01 continues to allow some amount of straightening even nearing ambient temp.
I dont have alot of knowledge working with steel. I did't realize I could have started the process from the start again. As well, I didn't think I could use water at any point in the process. All very good advice for my next one.
 
Never said it was good to start the whole process again, but you can. However, you will lose a little carbon just below the surface at each extra go at it. You can temper a hundred times with no ill effect, but it is best to get the hardening quench right just once. Yes. You can water quench a TEMPER cycle, but not the hardening quench process. Well, actually you can do it also, but be ready for broken blades. Once you gain a little experience, you can experiment with brine quenching, only with 10XX steels though. Brine is 13 oz salt per one gallon of water. It will give maximum hardness, although safer than water alone, but still carries some risk of breakage.
 
I'm not a bladesmith but I watch them on TV. :rolleyes: OK, I have proven my lack of personal knowledge. But, sharing what I frequently see on the 'Forged in Fire' tv show, there are often problems with warping and blade failure. Most of the contestants who get warping reheat the blade in the forge and hammer as straight as they can then reheat and quench. Sometimes they do this several times. Often those blades fail (break) during testing. The judges will say the reheating/quenching destroyed the grain structure of the steel weakening it. What I have learned from this forum and that show is that blade making with a forge is neither simple or instantly learned. I have great respect for those who do it well. And despite my frequent jabs at LRB for being a knife maker not from Arkansas, I include him in that group I respect.
 
Warp can be caused by a number of things. Uneven heat in the blade, uneven cooling in the quench, uneven/asymmetrical blade bevels, or shape, stresses in the steel from forging, stresses from grinding, lateral movement of the blade when it is in the quench, and a few other reasons. The one thing that does NOT cause warp, but is a wide spread belief that has been disproven over and over, is a horizonal quench that is not aligned north & south. If you intend to do a full quench, your best method is to have a tank allowing the blade to go into the quenchant point down first in. If you want an edge quench only, or just want a horizonal quench, it does matter in the slightest bit which direction the blade is pointing. It has been my experience that a vertical blade quench seems less likely to warp, but you may not have a tank that allows that.
RIFLEMAN1776, thank you for your words. We all just cannot be from that great state.
 
Everything LRB said is right in my limited experience. That said, I still place my quench tank north to south. Why? Because it makes me feel better lol. I figure I need all the help I can get some days.
 
Everything LRB said is right in my limited experience. That said, I still place my quench tank north to south. Why? Because it makes me feel better lol. I figure I need all the help I can get some days.
I'm not sure how I could place my 1 gallon tin can north to south.
 
I have found that a warped blade can be best straightened by anealing the blade. straightening, then rehardening and tempering. When hardening and tempering blades I always do it "hanging" never laid in the side.
 
I make cherries for bullet molds and a warp is not allowed. I found to put the oil can on my drill press with the cherry in the chuck to heat. When hot I stop the press and open the chuck to let the cherry drop straight to the oil. To quench a knife, enter oil straight. Any off center will warp. Let the oil cool the metal. I watch Forged in Fire and they pull the blade out with fire into the air. No good at all. Plunge straight and let the oil cool the metal. If the blade is sideways just a little you will get a warp.
 
I make cherries for bullet molds and a warp is not allowed. I found to put the oil can on my drill press with the cherry in the chuck to heat. When hot I stop the press and open the chuck to let the cherry drop straight to the oil. To quench a knife, enter oil straight. Any off center will warp. Let the oil cool the metal. I watch Forged in Fire and they pull the blade out with fire into the air. No good at all. Plunge straight and let the oil cool the metal. If the blade is sideways just a little you will get a warp.
Pretty much. Quench oil can/will catch fire if the blade or object being quenched, is not completely submerged. Having the quench oil burn shortens it's life span as a reliable and consistent quenchant. If you go straight in vertically, tang and all, you get a puff of flame, that goes out immediately. If you leave the tang out, you will get a short burn, until the tang cools below the combustion temp of the oil. Usually not a problem, depending on the blade size and the tang size. Just FYI. In the hardening process, most common steel does not harden until the temp drops below about 400°/450°. That is the temp range at which the conversion happens. Once the steel is below 900°in the quench, and you had the means to hold at a given temp in between, you could arrest the hardening conversion for how ever long you wanted, then cool it to under 400°, and it would then convert from soft to hard.
 
Pretty much. Quench oil can/will catch fire if the blade or object being quenched, is not completely submerged. Having the quench oil burn shortens it's life span as a reliable and consistent quenchant. If you go straight in vertically, tang and all, you get a puff of flame, that goes out immediately. If you leave the tang out, you will get a short burn, until the tang cools below the combustion temp of the oil. Usually not a problem, depending on the blade size and the tang size. Just FYI. In the hardening process, most common steel does not harden until the temp drops below about 400°/450°. That is the temp range at which the conversion happens. Once the steel is below 900°in the quench, and you had the means to hold at a given temp in between, you could arrest the hardening conversion for how ever long you wanted, then cool it to under 400°, and it would then convert from soft to hard.
On the topic of quenching, How critical is the temperature of the quench? For me, right now, I'm just experimenting/learning with knife building so I'm using only canola oil.
 
With most oils, 125°to 130°. There is one commercial quench oil, Parks #50, that is used at 75°to 100°, but it is costly although very effective for 10XX type steels, especially 1095. If you are quenching multiple blades, and the oil temp goes higher than 140°, it might be best to allow it to cool back down some. Warming the oil lowers its viscosity and cools the steel faster than cold or cool oil, however, if the oil gets too hot, it can slow the cooling effect. Each given oil will have its own boundaries, but to be on the conservative side, I don't quench much above 140°. If you are using canola oil, it does well with 10XX steels, and others. It is a fast cooling oil. Its drawback is that it has a short longevity in its effectiveness as compared with commercial quench oils. If your interest in knifemaking continues, you might want to consider buying a commercial oil down the road a ways.
 
With most oils, 125°to 130°. There is one commercial quench oil, Parks #50, that is used at 75°to 100°, but it is costly although very effective for 10XX type steels, especially 1095. If you are quenching multiple blades, and the oil temp goes higher than 140°, it might be best to allow it to cool back down some. Warming the oil lowers its viscosity and cools the steel faster than cold or cool oil, however, if the oil gets too hot, it can slow the cooling effect. Each given oil will have its own boundaries, but to be on the conservative side, I don't quench much above 140°. If you are using canola oil, it does well with 10XX steels, and others. It is a fast cooling oil. Its drawback is that it has a short longevity in its effectiveness as compared with commercial quench oils. If your interest in knifemaking continues, you might want to consider buying a commercial oil down the road a ways.
Thanks very much for taking the time to explain. I certainly need better equipment in the future, but so far the two I have made seem to be holding and edge.
 
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