Chisel-Ground Blades and Cutting Ability

James Y · Nov 7, 1999

I have some chisel-ground blades (I'm not referring to serrations necessarily, but knives with one whole flat side).

Does anyone else find these blades tend not to cut straight, or is it operator error on my part? Does anyone use a chisel-ground knife as their main or only carry, and what used does it get?

Currently I have a chisel-grind as an extra, or back-up knife, but my main blade is always double-ground for easier cutting.

Also: Has anyone here used a chisel-grind for outdoor work, i.e., fishing, hunting, etc., and what are the results? Just curious.
Jim

BARRY JONES · Nov 7, 1999

James,
My brother (Phillip) and I use the chisel grind on some of our knives. We use it on fighters and self-defense knives only. The chisel grind that we use goes all the way to an edge (no secondary bevel). This type of edge does not cut straight and is not for doing utility work (heavy use). We feel that it makes for an outstanding self-defense knife because you want to inflict the most damage with the least amount of effort. These knives, when done properly, are EXTREMELY SHARP.

The chisel ground knife, IMO, is for cutting FLESH only.

Hope this helps you.

Stay Sharp,

Barry Jones
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Corduroy · Nov 7, 1999

In my opinion and experience (take that as you will):

All that makes chisel ground knives so "sharp" is an incredibly narrow edge angle. Most knives are sharpened to 15-20 degrees per side, for an included angle of 30-40 degrees. Many chisel-ground blades have the samee angle on one side, but on one side only, the other is flat. This gives a total angle of 15-20 degrees. of course taht's sharp - it's also ridiculously brittle! I could sharpen a double-ground knife to a 20-degree included-angle edge, too, but I won't because it will chip like crazy.

A knife is simply a wedge. Normally this wedge is double-ground to make it cut straight when the user pushes naturally on the handle. In a chisel-ground knife this wedge is not in-line with the handle. Want to model the cutting action of a chisel-ground blade? take your favorite double ground knife and hold it rotated 3-5 degrees off of straight (so one of the grinds is perfectly vertical, like the flat side of the chisel-grind), then try to cut with it. Do you think it will cut straight?

I'm not saying that chisel-grinds have no advantages. For one thing, their ability to peel material away has made them suitable for kitchen use (right-side grind for "righties)) and the ability to lay the flat against the stem makes them popular grafting knives for gardeners (left-side grind for righties).
They also have one major advantage - they're easy to make, as there is no concern about keeping two grinds parallel and uniform, and meeting in a uniformly thick edge. This means chisel-ground knives can be made more cheaply and quickly than double-ground knives, and for some applications (e.g. a pure thrusting knife) the performance loss is negligible. The time/cost savings should be passed on to the customer, of course.

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johno · Nov 7, 1999

Almost all serrated knives are 'chisel ground' as the serrations are usually ground on just one side. They don't cut straight either.

David1967 · Nov 8, 1999

I have only one chisel ground knife -BM CQC7. I found it useful only for sharpening wooden sticks.

David

Scarman · Nov 8, 1999

I have the BM 975 and have hardly ever put it to any use. Not because I don't think they can cut(as they can be extremely sharp) but because I know the limitations of the chisel grind and what it was developed for.

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Gary W. Graley · Nov 9, 1999

I like the Chisel ground edge, even made a Tanto with that style of edge, and as Drew stated, Very sharp edge. Mine is out of A2 steel, heat treated to about 58 by Paul Bos and it doesn't seem to have any problems in the chipping area. I've chopped through some tree branches quite cleanly, RJ Martin, when I told him of this, took a second look down the edge of my knife to look for wrinkles or chips and found none. But I agree with the others that there is a control problem when cutting through stuff as it tend so curve away, but boy does it cut! I sit around the kitchen and slice stuff up all the time, might get a job as a confetti maker?, and the one that really slices almost anything is the chisel ground blades, leather is cut like it wasn't even there.
I put the picture of my Tanto on my web page, down near the bottom of the page.

G2

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Chiro75 · Nov 9, 1999

I have three chisel ground knives that I use on a fairly regular basis: two are Sean Perkins old Scythe Grind (convex grind on one side) and the other is a Running Dog Knives Little Pup, which has a concave chisel grind. All three cut very well, and they are a little harder to control than a standard grind, but I think once you get used to they way they cut it gets easy to make nice cuts. I can make as straight a cut with my Perkins knives in a continuous slice of four feet of cardboard (against the grain) as I can with a flat ground knife.

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SDouglas · Nov 8, 1999

Corduroy,

A Chisel Grind will not chip as much as a Double Bevel at the same angle all other things being equal. So they do tend to be sharper.

The Chisel Grind will inherently drift toward one side when cutting. This can be compensated for but it is there.

Are Chisel Grinds as good as or better than conventional Double Bevels?

It depends on the use.

I could go into a lot of physics, geometry and Trigonometry to explain why chisel grind and convention double bevel have these characteristics but it gets boring.

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AKTI Member No. A000370

Corduroy · Nov 8, 1999

"A Chisel Grind will not chip as much as a Double Bevel at the same angle all other things being equal."

Why?

The metal does not know what sort of knife it's attached to. An edge at a ceratin angle is identical regardless of how it was formed, by one grind or by two. I do not agee with your statement, please explain.

-Drew

Longden · Nov 8, 1999

Maybe the asymmetric nature of the chisel grind reduces stresses at the edge somewhat when the blade is deflected.

Just supposition ... I'd like to hear this explanation too.

SDouglas · Nov 8, 1999

Drew,

The difference in the geometries affect the force distribution. A Chisel Grind looks like a single Right Triangle while the traditional double bevel behaves like two back to back right triangles. I will have to take some time to refresh and work the Trig formulas but I recall that the key to the analysis was to look the double bevel as two back to back right triangles each with half the angle of the Chisel Grind and to prove that with a lateral force the contribution of the two triangles to resisting that force is unequal.

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AKTI Member No. A000370

Roger Blake · Nov 8, 1999

Logic is with Corduroy. Stress in blade is the force divided by the area. Since the area of the chisel grind is half its much more likely to bend or chip. I don't think you can find any physics to refute this.

Me, I don't like chisel grinds strictly because they don't cut straight.

JoHnYKwSt · Nov 8, 1999

I'd have to side with Drew on this one. Chisel grind, less metal behind the edge, thinner edge = more prone to chip.

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Johnny
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Chisel-Ground Blades and Cutting Ability

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