On 05/29/2010 10:58 PM, Existential Angst wrote:
lid wrote in message
...
Sorry for a bunch of posts at once. I worked all day long (almost) and
gave 1500 lbs of old junk to a scrapper.

Never had this problem before and I REALLY do not want to screw up.

The head of the Bridgeport CNC mill is attached to the turret with
four socket head cap screws, probably 1/2". They have a 3/8" hex hole.

All my attempts to unscrew them failed. I used a nice Unbrako L shaped
key.

Cannot do it without leverage.

With leverage (pipe) the key twists so much, that I really do not want
to push my luck.

I made a tool today from one 3/8" L shaped key: I drilled a
perpendicular hole close to the end of a pipe, and welded the straight
end of the key into that hole. So I can use the pipe as a lever to
turn the key without as much length to twist.

-. (L key)
pipe |
============|=

^ this end will go into the SHCS

I have no idea how will the key behave after having been welded.

I also have hex keys that are driven with a 1/2" breaker bar or an
impact. I am really afraid that it may somehow break the SHCS, which
would be terrible considering its job (holding the mill head).

Any comments?

Kroil, PB Blaster.
Build a little dam around the head to form a resevoir, let it soak
overnight.
Can make a big diff.
Also heat.

Thumping the head of the bolt with a hammer may help to break the rust
-- this is trying to achieve the same thing that Gunner is recommending
with his suggestion to tighten with an impact wrench and then back it out.

I'd thump it hard with a little hammer -- 1 or 2 pounds -- not a big
hammer. If you want to move a bit of metal a long way, thump it hard
with a little hammer. If you want to move a lot of metal a little bit,
thump it softly with a big hammer. You've got a little bit of metal
that you want to make sure to move...

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com