Edge thickness behind tip

H

Hesparus

Joined
Oct 31, 2004
Messages
1,442
Hi Everyone,

I've always ground a consistent thickness in my edge before sharpening. At 0.01 to 0.015 this is always fine. But lately I've been making some knives with finer edges (e.g. kitchen knives at around 0.003-0.005") and the tips seem too delicate. Do you guys usually leave a little more thickness behind the tip on your fine blades or grind the whole edge evenly?
Thanks,
Chris
 
Great question. I was going to ask the same thing. Two of my testers have broken tips, and both were under .010 prior to sharpening.
 
The tip, especially on a thin blade kitchen knife, can be quite frail. I usually steepen the bevel and edge angle as I come to the tip to provide more "meat" on the tip. Also, don't overdo the distal taper to much at the tip. It still needs enough metal to shape the bevels and sharpen. I have never measured it, but I would say that the spine ( and thus the actual point) at the tip should be about twice the desired edge thickness. If you like a .015" edge thickness, make the spine/point around .030" at the tip before you put the bevel on. Very thin edged blades, like a yanagi-ba, may need a little more tip thickness to support the edge.

Another reason for tip failure is poor HT. If you are using a 2BF or other less controlled heat source, the thin tip will almost surely be overheated. This will make it far more likely to break.
 
i'm new to this and never made kitchen knives, but i believe anything less than .015 would be risky for general purpose or utility knives, so of course depends on purpose, you want make a 'tactical' knife with .010 and you wont make a hunter with .03"
so what are the knives for?
that being said i know of several makers who do the point are slightly thicker on the knives that are made to take a beating and i did that couple of times too
 
I could see the first of the two being related to heat treat, but the second was under mich more strict temp control. I think I have been tapering too aggressively with not enough steel to support the tip.
 
another consideration for very thin tip kitchen knives: If you sharpen on belt grinder it is very very easy to overheat the tip and ruin the hardness there.
 
Most gyutos and other very thinly ground knives do thicken at the tip ever so slightly. I did some knives without this and it does make the tip too fragile. A slight thickening is perfect and if subtle doesn't affect performance noticeably at all. I usually just do consistent grinding but sharpen/reprofile the tip more on the stones to pull it back into the cross section to thicken it up as there is so little metal there that doing it on the stones provides better control and takes very little time.
 
You must log in or register to reply here.
Back
Top