Re: [CAD_CAM_EDM_DRO] Looking for spindles [cutters]

Jon,
Well, you can see the "case" surface layer along the ground edge and
examining a new cutter has the same dark color all over the sharpened end
and edge. It really looks as tho a post treatment has occured.
There is the usual brazed joint at the steel shank interface.
I'm mad and puzzled! I got stuck for what was advertized.
The long shank cutters are hard to find.
Has anyone used "Crown" brand engraving cutters?
RichD

Jon Elson wrote:

>
> 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