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David Billington

wrote:
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.

Maybe in Canada but in the UK A2 and A4 are commonly used for stainless
steel fasteners with no s on the end. The UK designation for the air
hardening tool steel was BA2 according to my link.

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.