Question on initial grind before heat treating on carbon steel ???

Lerch

Well-Known Member
Hi everybody

Well after the holiday break i was getting ready to start some more knives and after doing a little bit of reading on some Ed Fowler books i have a question. In his books if i am reading everything right he advises to initially grind your knife to just shy of 1/16" of where it will finish at. Heat treat the blade and then after grind away the excess 1"16th of steel. He said that grinding away the original excess 1/16" of steel would allow more carbon to be stored in the deeper steel that you expose. Just to state i am not 100% sure have read all of this right

My question is should i leave my grinds thick until i heat treat (grind them to 320 grit for clay quenching) and then after treatment grind away excess steel?? Or should i grind them most of the way down (keeping in mind i will have some decarb and scale to remove) take them down to about 400grit and just a few thousandaths from finished, then clay quench/heat treat??



I hope i worded all of that correctly,

thanks
steve
 
Mr. Fowler starts with big, thick stock and forges it down, requiring many, many heats to do so. For the methods he uses, yes, you would want to leave a lot of extra thickness to the blade, since every time it is heated above critical a tiny bit of carbon is lost from the surface of the steel.

For clayed blades, which are typically quenched in brine or a very fast oil to get the most activity to the hamon, extra thickness at the edge helps to prevent warping and gives the blade a better chance of surviving the quench.

In my practice, forging, then grinding, then quenching simple carbon steels, I prefer to leave a bit of thickness to the edge before heat-treatment, but not as much as Mr. Fowler suggests, as I generally forge from bar stock, not big rounds. I aim for the edge to be about the thickness of a dime before quenching. This extra thickness needs to be removed after heat-treating. The purpose of it is to have a good robust edge that resists warping in the quench (I have had blades warp badly if they are too thin, the edge ending up looking like a rippled potato chip), and so that the decarborized 'skin' can be removed without changing the profile of the blade. Note, I am heat-treating my blades in a propane forge, so a tiny bit of carbon loss is expected. If using high temp salts or some other type of atmosphere controlled heat source, there is less risk of carbon loss. A thin wash of clay can help prevent carbon loss in hardening, as can an anti-scaling compound.

I finish my blades out to 220 grit, then heat-treat, then I go back to a 60 grit belt and remove the extra thickness. A 15 minute soak at autenizing temp results in a very thin skin of lower carbon steel on the blade, and if not removed by regrinding the knife will increase in edge-holding and wear resistance the first few times it is sharpened as the softer steel is removed.
 
Thanks for the info, what you are saying is basically what i have been doing. I was afraid i was needing to leave them extra thick (like .075") before i did my heat treat. I have been grinding my blades down to around .040" , then heat treat and afterwards grind the last bit away.

Oh for the record i am doing stock removal on 1/8" 1095 steel.

thanks
steve
 
Coating the edge with anti scale or a thin wash of satinite should prevent nearly all decarb because if you are using stock removal you are really only heating the blade once for hardening. If you were forging to shape, I leave more than .040, personally.
 
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