question on zero grinds

C

clockworkfish

Joined
Dec 1, 2010
Messages
161
first off just how stable are zero grinds? secondly when making them do you still leave like a dimes width before heat treating and then just continue reducing the bevels after?
 
I wont comment on stability but you need to leave at least .010", maybe more depending on steel type. If you take it all the way to .000" before H/T it will probably look like a piece of bacon. Even if it doesn't warp you can and probably will lose some carbon thus effecting performance. I always leave .020"-.040" depending on steel type and what type of use the knife will see. I like to remove .008"-.010" from each side after H/T to be sure all decarb is ground away. Just my .02, others may do it differently.
 
They are stable like any other grind if everything is done correctly. I'd say zero bevel geometry is tough to get perfect but can really excel when done correctly.

Setting your angle before heat treat works well, it all depends on your grinding style.

I do a lot of chisel grinds and have one zero bevel on nearly every knife. It makes sense to me that a straight edge cuts aggressively.

If you imagine an arrow penetrating an object it makes sense to go in straight, not at an angle. In some ways a zero bevel keeps the angle straighter.

Of course there are many ways to make a knife well!
 
A zero'd edge's cutting ability is dictated by the bevel angles. The more acute the angle the better the edge will cut, theoretically. If there is no micro bevel added to the zero'd edge, you will be dealing with an ever disappearing edge as the bevel is sanded to thin it. When you get below a combined angle of 20 degrees at the edge, the edge gets so thin it is easily damaged if worked hard. Less acute say 24 or 30 its not so much a problem. With the addition of a mirco bevel either flat or convex, this can be alleviated.
 
On the blades I zero grind, I take them to about .010 for carbon steel and .005 for stainless, before HT. After HT, I grind to near sharp....carefully avoiding heat....and then switch to flat stones or diamond plates to finish the edge.

Most zero grinds are actually slightly convex ground at the edge. It is very hard not to round into the edge.

That said, there are very few blades that do better with a zero grind than they would with a small secondary bevel. Sashimi blades and microtome blades are OK as true zero grinds. Most all others should have a stroke or two done at about 15 degrees or higher to strengthen the edge.

Just to illustrate how small the edge angle is, a zero ground knife with a 1/8" spine and 1" tall bevel will have a 7 degree edge. That is very thin. Any abuse, even a minor bump, and it will chip instantly. Cut any hard materials and it will dull quickly.
 
I always put a microbevel on my convex knives. It makes them easier to sharpen for the average customer, and it strengthens the edge. I take some heat for it from the zero ground purists, but I write and back my warranty, not them. I am glad of this thread. Its nice to hear that at least my argument makes sense. Thanks guys.
 
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