Re: [CAD_CAM_EDM_DRO] Re: Leadscrews, PCB router experiment

JanRwl@... wrote:

> In a message dated 24-Jul-01 02:21:40 Central Daylight Time,
> elson@... writes:
>
> > The experts can tap the shank on their fingernail and listen for the ringing
> > of the cantilevered drill bit. If it rings with a very high pitch, close to
> > 10 KHz, then it is carbide for sure. HSS is magnetic, of course, but some
> > other cutter steels are not.
> >
>
> The most OBVIOUS way to tell "in an instant" is to "weigh" the piece in your
> delicate fingers! If it is OBVIOUSLY heavier than steel --- like LEAD would
> be, only even heavier, yet! --- it is solid-carbide! Dull grey, not shiny,
> like HSS.

Unfortunately, the drill bits in question are quite small, and the shanks are
often HSS or similar material, so the tiny drill bit's weight is lost in all
that.

> Carbide is even MORE magnetic than HSS!!! NOT a useful test!

I find this hard to believe. At least, PURE WC (Tungsten Carbide) is not
magnetic at all. The various commercial formulations often have large
amounts of Cobalt and other magnetic metals alloyed in them, which makes
them mildly magnetic. I just went into my shop to check this, and found
most of my "solid carbide" tools to be very slightly magnetic, although the
shanks of many of them were much more strongly magnetic than the
cutting end. I didn't fina any where the cutting end was strongly magnetic
at all, but the HSS tools definitely were.

Jon