Thickness before putting sharp edge on chef knife?

[skillgannon]

If you are doing a full flat grind and taking it down to .002 to .003 max at the edge the area above the edge is to be determined by spine height. Some guys take it a bit thinner. Another technique that I have heard of is to take it about .010 about 3/8" above the edge and convex to final. I is supposed to help with food release. My next one is going to be done that way.

 

[milkbaby]

If you're grinding a true full flat grind, then the thickness 1/4", 1/2", 1" or whatever above the edge is already predetermined by trigonometry between the thickness of the spine, the thickness behind the edge, and the height of the blade (between edge to spine). The only way it cannot be determined by these numbers is if it's not truly a full flat grind but some type of full convex grind, scandi grind, hollow grind, or compound grind.

 

[kuraki]

So....

(A) NO: I was not asking how thick/thin to take it down to at the edge just before sharpening it. (Or at least, that wasn't what I needed to know. But thanks to all who answered that!) Because I worded the question poorly, that IS, though, what many/most thought I wanted advice on. My apologies!

(B) What I was looking for was, again, what Scott Livesey figured out, and gave me: on a FFG chef blade, how thin to take it down NEAR the edge - say at 1/2" from the edge all along the length of the edge from heel to tip -- so that you've still got enough beef left?

Here's the reason: if I were to take a FFG 210-240 chef/gyuto all the way down to damn near zero at the edge, depending on the thickness I started with and how wide the blade is from spine to edge at the heel, I may end up with not a hell of a lot of metal backing up the edge. (Especially when I've got a customer who, despite being in Michelin, has a heavy hand with his way-too-coarse bench stone, and he wonders where a few mm of his blade width went after a few months - once I learned what he was doing, we had a little come-to-Jesus about sharpening technique...!) So for a thinner gyuto, I may want to do a not-quite-FFG, down to a few thou at the edge, and a little more of a bevel when I put the edge on, no? I'm trying to trade-off what the thickness I need to leave, at a certain distance from the actual cutting edge, is, like Scott was saying.

(Dang, I think by explaining I'm actually complicating. Sorry. :-(

I don't know how thick at the point you're saying, but if you took the edge down to .020" and then used a mild convex grind to get it down to 0 at the edge, that rose up about 1/2" I think it would do what you want.

 

[One Armed]

If you're grinding a true full flat grind, then the thickness 1/4", 1/2", 1" or whatever above the edge is already predetermined by trigonometry between the thickness of the spine, the thickness behind the edge, and the height of the blade (between edge to spine). The only way it cannot be determined by these numbers is if it's not truly a full flat grind but some type of full convex grind, scandi grind, hollow grind, or compound grind.

I’d say this pretty well answers the question. The area BEHIND the edge is determined by type OF & angle OF bevel grind leading up to determined thickness of edge, prior to final sharpening. It’s as milkbaby said, trigonometry.

 

[jdm61]

If you're grinding a true full flat grind.....

Which can be a big IF. I don't leave a plunge cut on my kitchen knives and I don't "bevel" the tang, so all of them are, by nature, somewhat convex and blended and typically more convex up near the heel. The belle is also slightly shorter at the heel than say an inch down the blade, so the bevel angle is slightly different. Your mileage may vary.