"DoN. Nichols" wrote in message
...
In article ,
Harold & Susan Vordos wrote:

"DoN. Nichols" wrote in message
...
big snip---

I'm not sure, but I *think* that drill bits may even be two
part, with the flutes being HSS, and the shank mild steel.

They have that appearance, but they are induction hardened, so there is a
very distinguishing line where heating and hardening ends due to the
rapid
heating. The entire drill should be the same material.

O.K. That explains the differing hardness. I wasn't sure how
soft HSS could be made, which is why I was speculating the two-piece
construction.

Thanks,
DoN.

While I'm not privy to the exact speed at which the shanks get heated, I
can relate one personal experience, that of watching a splined shaft for an
armored personnel carrier getting heat treated by induction heating. The
shaft, about 1-1/4" diameter, was placed within the induction coil and went
from ambient temp to quench temperature in something like 20 seconds. That
is, of course, a function of the power of the induction power supply. The
larger (more powerful) the unit, the faster the heating. Typically, the
heating occurs at such a fast rate that there is precious little travel of
the heated area(s). It's not uncommon for heating coils to heat specific
areas of items, leaving the balance of the article it its original state.
Induction heating is really a great way to go, although rather expensive to
set up initially.

Harold