Re: [CAD_CAM_EDM_DRO] Looking for spindles [cutters]

RichD wrote:

>CL,
>Speaking of engraving bits. Last week I finally discovered the answer to why,
>after several sharpenings, the edges on Antares "solid micrograin carbide" cutters
>would instantly break down when touched to metal in the usual operation.
>After many repeated resharpenings and microscopic examination, the evidence struck
>me. What I noticed was a difference in color between the unground surface flat, dark,
>and the core metal, much lighter. These cutters are case hardened. Once you grind back
>to the core material, they chip and crumble very easily. Trash!
>A new cutter performs as expected, even with their crude sharpening. It appears as
>tho they are case hardened after sharpening.
>
>

Can't be. Case hardening works for steel, but is meaningless on real
carbide. There is
no heat treatment or other process for hardening or annealing carbide.
What I suspect
is these things are not SOLID carbide, but some sort of compound
construction with
a softer steel core and a carbide exterior.

Another possible explanation is they are made by powder mettalurgy, and
either the
process creates a tougher carbide on the exterior, or they actually make
it with a
different composition or crystal configuration on the exterior.

Jon