Newbie to the Knife Building World

buck98j

Member
I have recently started building knives by stock removel with a homemade 2”x72” grinder and heat treating in a gas forge I made from an old one room woodstove that I lined with fire brick.
I have a question I would like to ask to anyone who might be able to help. What is the proper procedure to fix a blank that has been heat treated and then got a hotspot with discoloration on the secondary bevel during final grinding/polishing?
Any help would be greatly appreciated.

Thanks Buck98j
 

Doug Lester

Well-Known Member
Two things. One is to re-grind the blade but that often, if not usually damages the profile of the blade. The other would be to normalize the blade and re-heat treat it. When grinding you need to keep the blade moving and keep a container of water at hand to cool the blade often.

Doug
 

buck98j

Member
I appreciate your quick response Doug. I was frequently dipping it but the edge is very thin near the tip. I think I can hand sand and it will look fine. I was more worried about having a brittle spot where it got hot. It is made of 80crv2 and is still nice and flexible and returns to form. I will finish it and see how it responds when I sharpen it. Thanks again!
 

opaul

Well-Known Member
If the tip is soft or brittle from over heating it will be apparent if you drop the knife point down on your anvil.
 
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opaul

Well-Known Member
It’s easy to get the point too thin when grinding the taper in.
Also after HT and tempering it’s best to use new fresh belts to complete the finish grind. As has been said before use belts like they are free. Old belts, especially 100 grit up generate a lot of heat when past their prime which does not long. I’m very guilty of this.
 

Chris Railey

KNIFE MAKER
Also, if you have the ability, slow your grinder speed down when working on thin sections of your blade. If you cannot slow your grinder down, I would suggest looking into ways to give yourself that ability. Until you can slow it you can use less pressure when grinding thinner sections that will help a little too. One more tip on over heating on a grinder. When you cool your blade in water leave it in for a few seconds to cool it all the way back down. I see many people do the half second dip in water and then back to the grinder. The blade will retain heat this way making it easier to overheat.
 

Chris Railey

KNIFE MAKER
Thanks for the tips. I guess like everything we learn, it takes time and unfortunately mistakes.
Shoot I have burned my share of edges for sure. Most of them before getting a variable speed grinder though. I hesitated to say this earlier because I do not want to come across as contrary to what others have said. In my opinion, If you got your edge hot enough to change colors, bare steel to blue, for example then you lost your temper in that spot and it will be softer than the rest of the blade edge. Some may say it will be brittle but the fact remains it will damage or dull before the rest. When I do that if I have enough steel left to heat treat again then I do so. If I do not have enough left to HT again that knife will never leave my possession if I finish it out because I cannot be sure of its quality. Just my opinion.
 

buck98j

Member
Chris, if I were to put it in a foil packet to re- HT, would I lose less mass? And do you have to remove from packet before quenching? I know my best bet would be to ditch it and start over, but I don’t like to waste material and time.
 

buck98j

Member
Forge, I have all of the materials ordered to build an oven. That will be the next line of questions.
 

Chris Railey

KNIFE MAKER
I have never used foil so I cannot answer that one. You can still finish it I just wanted you to know that more than likely there’s a soft spot or weak spot in your edge if you change the color post heat treat. In those cases if I finish one out like that I just keep it and use it around the shop or in my own kitchen or something.
 

buck98j

Member
Thank you, nice to join such a positive group of people. It’s very nice to be able to converse without all of the nit pickers. Constructive criticism is always welcome but the other BS is not. Have a great day!
 
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