"Rick Hughes" wrote in message
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"Dave Baker" wrote in message
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"Rick Hughes" wrote in message
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I have an expensive item that is manufactured from Billet Aluminum.
It is assembled with 316 stainless steel csk hex head screws.

I need to disassemble and the screws are stuck fast.


The heads are 7/32" hex imperials (yep 100% sure - It's a US
manufactured product)

I have tried encouraging Allen key with mallet - no good.
Applied releasing oil - no good (happy to try a specific product if
there is a particularly good one)

So far only one of the 8 have come out !


Now one way to approach this would be to use an impact driver ... I have
a compressed air 1/2" square drive impact driver, and assorted sockets
... but would need a 7/32" hex insert ............ anybody know where I
can get one

First off you might want to read this.

http://www.pumaracing.co.uk/ToolUse.htm

Countersunk fittings do tend to lock on very tight because of the angle
and area of the underside of the head. You need to shock these loose with
something other than an unmodified right angled allen key which can't
really be hit directly on the end very easily. A small brass or bronze
drift is ideal, especially if you can machine a pip on the end in a lathe
to keep it centred inside the allen screw so it doesn't jump about and
mangle the aluminium around it. Or just cut a bit off an old 5.5mm allen
key and hammer that. By mallet I assume you mean a wooden one. You *must*
use a steel hammer to get a proper shock loading on the drift. Hitting
something with wood will achieve three fifths of FA. If they still won't
come out hit them harder! You won't hurt anything. It's like training a
dog. Once it really knows who's boss it'll give in and stop dicking
about.

To use an allen key in your impact driver simply cut a length off the
long end with an angle grinder disc and use it in a 7/32" socket.

Absolutely no point using releasing oil. The joint will be fluid tight.

You also must tighten back up each screw you loosen to take the load off
the others and when all are free remove them one at a time.

If the screws are loctited in then applying heat for a while will soften
it.

Car engine oil pumps are often held together with csk allen screws and
I've had to remove god knows how many ultra tight ones over the years but
nothing has ever failed to succumb to the right technique.

I'll bet you a pound to a pint if you cut a bit off an old 5.5mm allen
key, belt that firmly with a claw hammer a few times and then just use a
good tight fitting 7/32" key they'll pop out as easy as anything.
--


Tried some heat ... no difference (don't want to apply too much)

Bought new set of metric Allen keys to make sure it's a good fit ... still
no go.

I have now ordered a socket driven allen key .... I'll give that a go with
my pneumatic impact wrench .. on lowest setting and low air pressure.

My worry is it it rounded off the screws .... be a major issue to solve.

Not really. You just drill the heads off and you're left with a bunch of
easily removeable threaded stubs after the cover is removed. Just use a
drill a gnat's bigger than the screw shank and drill until the head spins
off.
--
Dave Baker