Noob Question - Edge Thickness

B

bunghole

Joined
Jul 6, 2005
Messages
206
Hi,

I'm doing a flat grind on a kitchen knife (440c). The steel is 1/8th inch thick and the blade width is 1 1/2 inch at it's widest. I'm kind of eyeballing the angle of the grind, so if anyone has any thoughts on that, it would help, but more importantly, I'm wondering how thick the edge should be before heat treating. Also, what tolerance in edge thickness should I be shooting to achieve before heat treating? Or what variance in thickness is acceptable?

Thanks for any help or advice!
 
When I build a kitchen type blade, or just about any other blade that is 1/8" or less, I heat treat the blade and then grind the bevels... it helps keep any warping to a minimum, which saves the maker a lot of grief.
 
Since you are a noob, I am going to assume you will send the blade out for heat treat. You would do well to talk to the heat treater. When I worked in 440-C I sent mine to Paul Bos. He told me to take the blades right to the finished edge thickness that I would sharpen them at, and at what ever level of surface finish I wanted at or above a 220 grit finish. I was very pleased with his work.
 
I agree with Ed. 1/8" thk blades get HT first, regardless of steel type.
 
Very good advice here.

Right now I'm working on my own 1/8" thick kitchen knives. The steel CPM M4 heat treated by Paul Bos to 64Rc. Right now, I'm wishing I had taken the bevels thinner (about .015") before heat treat. This stuff is hell on my 40-grit Blaze belts, and it's way worse now that it's hard. Large commercial heat treaters like Bos are set up to treat thin blades with a minimum of warping.
 
I contacted Paul Bos and his suggestion was to leave at least .030" on the edge and to finish to 220-300.
 
I think paul is being a victim of his sucess, everyone I know is sending thinner more finished blades because they all turn out so perfect, One of these days we are going to reach his expert limit and all be saying on my god, he bent my blade. I finish to 220 with about 0.020, thin out a little more when I get them back but maybe I send them a little thinner, hmmm.
 
Patrick, he did send 2 or 3 back to me warped. I sent them back, and the second time around, perfection. This was in the eighties. No one is perfect all the time, but Bos is close. I do my own HT now, in 01, and I take them down to within a few thousandths of completion. I would rather straighten a warp, than have to grind hard steel.
 
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