"Tim Wescott" wrote in message
...
I'm looking for product names to look for.

I'm working on an instrument for a customer, and he's having me do the
whole-system design. This means I'm out of my comfort zone and playing
with mechanical issues.

It needs a big outer case (well, four feet long, by nine inches by two).
I'm thinking of doing the outer case from fiberglass for a number of
reasons, not least of which because I'm familiar with its
characteristics, and the instrument is going to be used on or near bodies
of water including salt water.

I'll need to attach things to this outer case. My current thinking is to
used buried studs and/or nuts, and use thumb-nuts and thumb-screws to
actually attach the bits. I'm assuming I want to use brass or stainless
hardware for corrosion resistance, and I probably want to take some pains
to match alloys.

McMaster is failing me for appropriate hardware. I'm finding thumbscrews
and thumb-nuts, but I'm not coming up with good candidates for nuts that
I can bury in the fiberglass. I'm assuming that the case will be a two-
part assembly that's glued together; nuts that can be buried in one side
and then captured in the gluing-up process seem to be the best notion to
me, but if someone with actual experience has alternate suggestions, I'll
listen (I may not _take_ your suggestion, but I'll certainly _listen_ and
_think_ about it).

So -- suggestions? I'm probably wanting some 4-40 or 6-32-ish sized
ones, and some 10-24 (or 1/4-20). The bigger ones may work better as
studs, with thumb nuts. I'm pretty sure that I want nuts for the little
ones, unless that presents severe difficulties.

5052 aluminum is fair for a marine environment, and it welds easily. It
doesn't machine as well, but it is possible to machine it too. That might
be an alternative for your shell. It can be drilled and tapped, but again
it can be a little finicky. 6-32 into 5052 would scare me, but I have done
it. 10-24 and 1/4-20 should be fine. I have heard 4-40 is easier than
6-32, but I have not done it.

I'm not sure about embedded nuts in glass, but stainless t-nuts are
available. Usually they are used in wood by driving them into the opposite
side as you are bolting from. If you do an encapsulated wood and fiberglass
design I am sure It would work, but I am not sure how long it would hold up
in your environment. In boat building they usually bolt through rather than
into glass or glass composite. The holes are sealed during the bolt through
assembly process. Occasionally screws are shot into glass, but they are
very low load applications, and the holes are sealed from one or both sides
as applicable.

Is your fiberglass plan for a sprayed or laid up shell in a mold, or do you
plan to use some form of a core? Or both? Fiberglass boats for example use
all of the above. A shell is sprayed into a mold, a core is added for
strength, and additional glass is sprayed and/or hand laid. I imagine if
your layup is heavy enough to handle any loads you probably can embed t-nuts
with a stuf already in them to provide a hole for your machine screw later,
(if you can find the right sizes) but it might be a tricky process. I am
sure a mold release would be needed on the stud.