On Tue, 27 Sep 2011 19:47:54 -0400, "Phil Kangas"
wrote:


wrote in message
.. .
On Tue, 27 Sep 2011 17:16:20 +0100, David
Billington
wrote:

Harold & Susan Vordos wrote:

wrote in message
...
On Sun, 25 Sep 2011 18:43:04 +0930,
"Kevin(Bluey)"
wrote:

On 9/25/2011 6:00 PM, Harold & Susan Vordos
wrote:

wrote in message
...
snip--
Many set screws actually harden with
heating - from my experience

I'm having more than a little trouble
believing that. I'm not aware of
any set screws being made from
precipitation hardening steels,
although
I do suppose they could be. Beyond that,
the only way the screw
would be
harder is if it was heated rapidly, heating
only the screw, so the
surrounding material behaved as a heat sink
and quenched the material
while the carbon was still converted. Sort
of like a chilled iron
casting. I'm having a problem with the idea
that that happens,
especially when heating by torch.

I'd suggest that a fast heating to a dull
red heat would anneal the
screw. Once annealed, whether it backs out
or not (it may, for the
heat
will have also disrupted the rust that has
formed), it will be dead
simple to drill out. Drilling to the minor
diameter of the screw
should
result in a clean hole with threads
entrapped, like half a heli-coil.

Harold


Im with you Harold . Never had a set screw
harden when heated .

The vast majority of cup end set screws are
either A2 or A4 steel -
which is by definition an air hardening
steel - and WILL harden when
heated. Just like most exhaust studs. They
are hard enough to start
with, but if you heat them trying to get them
out they end up as hard
as glass. Very hard to anneal, particularly
when jammed into a
casting.
The advice regarding spot heating the screw
is good advice , I have
used
this procedure a number of times and it
works .
Works particularly well in maleable iron
pullies etc, as it enlarges
(in) the hole, then shrinks back, leaving a
looser fit

Soaking in a good penetrating agent is also
good , in conjuction with
the spot heating

If you can get a left hand drill the minor
diameter of the screw thread
, some times the drill will grab and screw
the screw out for you .


Both A2 and A4 are considered
stainless---which, to my knowledge, is
not the screw in question. I would fully
expect that most socket
sets are made of high carbon steel (which is,
in fact, an *alloy*),
which readily anneals. Could be wrong, but I
can't find anything
online to support the notion that they aren't.

No, A2s and A4s are stainless.

I welcome anything you can provide to support
your claim that they are
precipitation hardening.

Harold
I know of A2 and A4, IIRC 304 and 316
respectively so wouldn't be
hardenable by heat treatment but I was wondering
if he was referring to
A2 air hardening tool steel. Not seen a mention
of A4 tool steel.
http://www.westyorkssteel.com/tool_s...fications.html

That's what I'm talking about. And I've run
across MANY setscrews over
the decades that could barely be touched by a
normal drill, and could
NOT be touched by ANY drill after heating.

Before being heated, a good cobalt drill, at low
speed, in a positive
drive drill press, will handle most - but pretty
hard to mount the
garden tractor in the drill-press vice. If the
drill spins instead of
biting, the heat hardens the screw and you are
DONE.

Same kind of steel as used on grader blades.

The set screw of interest in this thread is
obviously not stainless! It is
rusted in place. Stainless set screws are _not_
common, they will
work harden if touched with a dull cutter. As far
as annealing a high
carbon set screw it definately can be done! I've
used quite a few
to make stripped thread repairs. I line them up on
the bench vise
on wire butts and heat them with a propane torch
and let them cool
naturally. They will then be capable of machining.
No problem.
They can be re-hardened after too..........if you
want.....
Grader blades are a manganese alloy steel, work
hardening, but
can also be annealed, if treated properly. Why
would set screws
be made of a manganese alloy? I don't think
so.....;)}


You could likely anneal it if it was out of the casting - but it will
likely cool too quickly in the casting.