edge dimension needed to prevent 'melt'

M

muntag451

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Jan 4, 2008
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presently working on a tactical knife design and need your help: how thick (thin) should the edge of the knife be PRIOR heat treating it?? I KNOW that I can't bring it to a sharp edge prior cause it will get damaged while heat treating (or so I am told)
Can I dare go as thin as 0.0325 inches??? Thinner? How much? The blade stock is 4 mm thick (0.18 inches) at the spine.

any info is appreciated. I am in the process of cutting from the stock stuff, and I will cut 3 knives, each with different edge thicknesses. Your info will be greatly appreciated as it will allow me to prepare the edges and shorten my learning curve.

as far as the heat treatment recipes, I think I got plenty of suggestions just by reading prior posts!!!
 
It depends on the steel and how you're heat treating it. For example, if you're using an air hardening steel which requires a long soak at high temp and you're not using any kind of protection from oxygen, you should leave it .060" so you can grind about .020 from each side to remove steel with carbon loss.

Or, if you're water quenching W1, you'll need to leave it thick so it doesn't warp. Or oil hardening should be kept 1/16" or more so the edge doesn't get waves, then ground thinner after HT.

An air quench steel in foil with plate quench you can go down pretty thin without problem. .020 shouldn't be a problem.

What kind of steel is it, and how are you going to HT it?
 
I usually recommend .030 to .040 ,so you seem fine. Like muntang said, it does depend on how you are doing the HT, what the quench is, and what the steel is.
Stacy
 
I shoot for .010 lately without issue, and some I did today, I took to a zero edge.
CPM154, 1/8"

A lot of it has to do with how you removed the metal too.

You can leave it thick, and still have warp if you removed the steel unevenly.
 
i have found if you have no way to control temp and you need a long soak a very thin edge will burn off and worp. leave it thicker and your good to go.
 
JTknives said:
i have found if you have no way to control temp and you need a long soak a very thin edge will burn off and worp. leave it thicker and your good to go.
Click to expand...
True enough...
I forget everyone doesn't have a decent oven.

Another thing to consider is what angle you will sharpen at.
If you are going to have a shallow angle for the edge, you need to grind thinner than if you are going to have a relatively steep angle.

Say you are bringing your grind up 3/4 of an inch from the edge on 1/8" material.
Sharpening to 20 Degrees.
.020" edge thickness will give you a primary bevel of .094" HUGE

30 Degrees = .050" Better

Now .010" edge thickness gives you
@ 20 Degrees = .050"
and 30 Degrees = .026"

This edge thickness only matters before sharpening of course.
I know a lot of people do a substantial amount of grinding after heat treat.
I don't like to do that, all I do after heat treat is clean up the blade.
They are basically finished before they go in the oven.
 
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