On 2012-02-25, Ed Huntress wrote:
On 25 Feb 2012 05:55:43 GMT, "DoN. Nichols"
wrote:
On 2012-02-24, Paul Drahn wrote:
On 2/23/2012 8:18 PM, Richard wrote:
On 2/23/2012 9:54 PM, Karl Townsend wrote:
I need to make a pin .25" long by .096" diameter with a 0.109 by 0.117
head. It needs to be hard so I'll make it out of a 7/64 drill bit, the
size of the head.
Note that most drill bits have a soft shank and a HSS blade, so
the shank won't do much for you. I don't think that it has enough
carbon to harden well at all. (If you only need the surface hardened,
you can get some Kasenite or other case hardening pack material for heat
treating it.
Don't case-harden HSS. The shank has plenty of carbon -- and chromium,
and probably molybdenum, to harden it up to over Rc 60.
Are you saying that the shank of a typical drill bit is also
HSS? I've always understood them to be mild steel welded to the HSS
which implements the flutes and other cutting surfaces.
I was assuming that if he used the shank, and had to harden it,
it would be mild steel, not HSS, so I was not advising case-hardening
HSS.
However, it's not a good idea to do so. There are too many other
things going on with HSS alloys; you risk winding up with a weak part
unless you have good temperature control.
And it is likely that *if* the shank is really HSS, you won't be
able to machine it anyway, unless with a toolpost grinder. :-)
Note that a heat-and-quench hardening will harden HSS, but it won't
make it "high-speed." HSS requires a two-stage heat treatment in order
to develop red hardness, and the second stage is a
solution/precipitation hardening that is a real challenge in a home
shop. It can be done, but you have to know what alloy you're dealing
with and you have to know just what you're doing. You also need *very*
good temperature control.
Not at all what I was advising.
Music wire or oil-hardening drill rod would be much preferred. They
can be easily and reliably hardened and tempered.
Agreed. Much better choices than old drill bit shanks.
Enjoy,
DoN.
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