That just made me think of something. If the bottom of the countersunk
hole doesn't match the profile of the fastener where the head meets the
shank then there's is your problem. The fastener has a bit of an
interference fit at the transition point, and right away the bearing surface
under the fastener head isn't fully making contact because of it. However,
the aluminum "flows" from the stress and lets the bearing surfaces bear down
on each other. Add in a little galling from dissimilar metals, finish
differences, and you have a bind.
Apply a bit of oil or something on the fastener then run a couple in and
back out just once in the time frame you have the issue with. Compare the
bottoms of the holes with and without the fastener and look at the bottom of
the hole at the transition point I mentioned above. If you see any profile
changes, you likely have this issue.


"Tom Gardner" wrote in message
. com...
| How about doctoring the countersink bit to a slightly off-angle to create
| less surface area contact. Try counterboring the threaded holes a few
| thousandths to allow for a little deformation before it jams. How about a
| bigger tap drill. Are you alligning the length of the screw with the
| magnetic pole?
|
| "Joe" wrote in message
| ...
| We use some decent flat head screws on our units and I've run into a
| strange problem. When we tighten them into the aluminum housings, they
| hold a galvanized plate in place. After about 10 minutes of being on
| there, they are almost impossible to get off.
|
| We have turned the highest quality allen keys we can find into pretzels
| and have stripped many using impact and a shorter length. Sometimes we
| have success by using a chisel to "spin" the flat head loose but that's
| the Neanderthal method I'd like to avoid... Even that fails 50% of the
| time. We can't use heat because there is a rubber seal in the aluminum
| very close.
|
| The flat head actually grabs onto the galv. plate so well that our
| customers (and us!) have to drill them out 8 out of 10 times we need to
| remove them...
|
| Anyone know of a super allen key or some other method of removing these
| that might work? We know that when we use painted plates, we have less
of
| a problem and have considered painting the countersink of each flat head
| hole, but that's crazy in the big scheme of things...
|
| Thoughts, wisdom and random visits from friends welcome.
|
| Regards,
| Joe Agro, Jr.
| http://www.autodrill.com
| http://www.multi-spindle-heads.com
|
| V8013
|
| My eBay: http://tinyurl.com/4hpnc
|
|
|
|