warped edge advice

samuraistuart

samuraistuart

Joined
Dec 21, 2006
Messages
3,158
So now I'm scared to death. Made my edge a little TOO thin on the Blue Steel chef's knife. There is an area about the size of a nickel along the edge that warped out maybe 1/16". What does one do here....or is there anything that CAN be done? I am very familiar and good at the 3 point clamping method for straightening bends along the length of a blade....but that isn't going to help here. I thought of doing something similar.....just using my C-clamp after one temper has been done, and clamp down on that one spot and temper again. The only problem that I can see there is usually a bend must be "over-corrected" to end up straight...and simply torquing down on this with a clamp will not "over-correct" it. I may try to come up with some sort of mini 3 point system...i dunno.

I am very frustrated and disappointed with myself right now. Tried to go as low as I could on that edge thickness, but alas it was too thin. What was it? I didn't mic it but it was getting close to .010". The spot affected was thinner than the rest of the edge by just a smidge....my grinding wasn't too perfect. The rest of the edge was about .015" and looks great. I try to get as close as I can to final edge thickness (with decarb to take into account). But I seriously need to start leaving more meat on the edge and deal with it after heat treat. Live and learn. Cussing and screaming falls in there somewhere, along with objects hurled at hyper velocity across the room.

Carbon steels should have at least .020" on the edge, dummy.
 
Do you need a boning knife? :D

Try a mini three point clamp like you plan. Use a coin on either side of the warp, and the clamp in the middle. Otherwise narrow it down and make something else useful out of it. I have a few like that, including a san mai blade that I was really disappointed to warp.
 
If it isn't a big area or warped too far, just heat it and a block of flat steel plate in the oven to 400F. Let soak for about 15 minutes. Set the hot block on a board (anything that isn't metal) and place the hot blade on it and tap the warp straight with a small brass hammer. I keep a 4X4X1" piece of smooth steel just for such tasks. The mass of the block will keep the blade around 400F for more than long enough to straighten it.
 
Thanks so much guys!!!! I feel a bit better.....believe it or not. She is in the oven right now at 390F with a 3 point system. I was able to get that small "bad" area over corrected. I REALLY don't want to go any higher temp than that, but will if I have to. I hear 400F is the magic number for straightening bends. Stacy.....that is a splendid idea. If the 3 point method won't "cut" it....I'll try your suggestion. Surely THAT would work, wouldn't it?

Who is Surely?
 
Well, guys the 3 point clamp system just didn't work for an area that small. While the bend is not quite as far now...I have managed to introduce another slight bend....so now there is an "S" about a centimeter in length on the edge, but only about 1/32" warp. Stacy, your suggestion is next....and I have high hopes. I've got the scrap steel and a small brass hammer. Tomorrow I'll tackle it. Why can't things just fall into place every now and then?!?!? :)
 
I hope to hear how this works as I have the same issue (not with a kitchen knife though) and have tried using smaller and smaller items for over correction. I am about to throw it back in the oven and start all over again.
 
One thi9ng to remember is that these things can be easily fixed between 900F and 400F. You can use your fingers or a hammer. I have a wooden plank that fits on the anvil and my lignum vitae "swacker" to adjust any warp or twist that my hands can't get. I also have a variety o slotted boards to twist/bend the blade in if needed. The austenite is like rubber compared to the martensite that will start to form around 400F.

That said, I rarely have to do more than give a blade a gloved hand tweak to have everything straight.
 
Stacy, you and I are on the same wavelength quite often. I bought a pair of thick gloves exactly for that purpose (straightening a blade between 900-400). I had them on, pulled the dude out of the kiln, submerged and slightly agitated in the Parks, and when I pulled it out, I scoped down the blade. Dead straight. "Yes", I'm thinking to myself.....no need for straightening this time!!! Hooray! And about the time it cooled enough to handle with bare hands....I saw that slight warp on the edge. Too late too late. It is slight...but not small enough to grind out when sharpening. To be honest, even tho now it is a slight "S" curve, it is only half as "bad" now (instead of being a bow at 1/16" it is an S curve about 1/32"). When I lay the edge down against a flat surface.....the bend is just noticeable from dead straight.

And concerning the brass hammer.....turns out mine was brass plated. Not going to work for me....but I do have a brass punch, and the head is about the size of a dime. I polished the head up and made it just slightly convex, so as it is not dead flat, and I'll use that instead (with my small hammer). My plan is to put the blade, steel block in the oven at 400F for half an hour total, slide it out on the rack it's on, and try to quickly tap the defect back in place. My hopes are high, but my knees are knocking.

Next quench I should pay much better attention, and leave a bit more steel along the edge. .015" is just asking for it with carbon steel.
 
Everyone should get or make a simple brass hammer. A piece of 3/4" or 1" round stock 3" long will make one nicely. I keep the face flat with a slight chamfer around the rim.
 
This isn't working too well. I think the issue is needing a brass hammer, instead of trying to transfer the force through the punch, which I did flatten the face out. The first try, I think the face was too rounded. That and maybe heat retention. I put gloves on, pull out the rack in the oven that has the cooking stone, and the layers of steel, and then the knife on top. I quickly place the punch in place and pin the blade down with one hand and strike with the other. It doesn't seem to want to straighten out....but I'm still trying this out....still in the oven. I might just have to bring the edge up a smidge.....it won't be exactly like I wanted it.....which will drive me nuts.....but it should be OK looking....and work.

Well....to give an update and contradict myself....it IS working. After one more cycle or two.....should be good to go. Stacy...thank you!!! Excellent tip. 400F seems to be the magic number, for sure. 395F was pretty stubborn. 405F is working decently. If I had a proper brass hammer, one or two cycles would have this done.

Cannot WAIT to sharpen this baby up and try it out now!!!
 
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Most folks are afraid of 400F and higher. Even 425 or 450 will leave a good hardness on blue steel.

Glad it worked out...now get/make a small brass hammer with a flat face.
 
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