Epoxy resist?

[_]

I'm modifying a cheap plastic film camera to do 'B' shots (star trails) and
I need to fix a pivot to the case; a small blade passes though a slit to
push against the original shutter so it'll stay open. I would like to
solder a shaft to the blade and epoxy blobs to the ends of the shaft so
they are held but free to turn. Grease? bakers parchment paper?

[sta...@prolynx.com]

On Feb 15, 9:39 am, _ <jtayNOSPAM...@hfDONTSENDMESPAMx.andara.com>
wrote:

Scotch Magic tape is what I use on woodworking projects, you have to
time it just right so the glue is set, but not too set to get it out
of the corners. For your application, you could probably let it set
up hard before pulling the tape. You might want to check first to see
that the backing doesn't dissolve in the epoxy.

Stan

[IanM]

Its going to be *fun* getting scotch tape out of the pivots. Trouble is
*most* hydrocarbon lubricants have poor compatibility with many plastics
and you need something that will stay put and not contaminate the glue
joint. The other problem is thermal expansion of epoxy is way different
from that of metal, Ideally fabricate metal pivots, lube the shaft with
a very little silicone grease in case any epoxy gets where it shoudn't
then glue the pivots down. Otherwise the 'gold standard' mould release
for fibreglass work is PVA (PolyVinyl Alcohol - NOT white glue!) and if
you know anyone in the trade you may be able to beg a little bottle
full. I'd apply that to the shaft over a layer of paraffin wax (applied
hot) if I was going to try and wash the wax out for a free action or
bees wax if I wanted to leave the wax in for lubrication and controlled
friction. If you canrt get PVA, try bees wax on its own. Some
experimenting is called for. Are you sure epoxy will stick reliably to
the camera body? Aluminium or brass bearings fixed with minature self
tapping screws may work better.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL:

[Mark Rand]

On Mon, 15 Feb 2010 22:53:01 +0000, IanM <look.in...@totally.invalid>
wrote:

>PVA (PolyVinyl Alcohol - NOT white glue!)

Had a row with my woodwork teacher at the age of 12. He was bigger than me and
won. But I was right!

:-)

Mark Rand
RTFM

[Don Foreman]

The term you want is "release agent". Petrolatum (Vaseline) works.
Kiwi neutral shoe polish is the preferred release agent of at least
one guy who beds rifle actions in epoxy for high accuracy.

[Richard J Kinch]

IanM writes:

> Otherwise the 'gold standard' mould release
> for fibreglass work is PVA (PolyVinyl Alcohol - NOT white glue!) and if
> you know anyone in the trade you may be able to beg a little bottle
> full.

Polyvinyl alcohol used to be sold as a hard contact lens wetting solution.

[Doug Miller]

No, not really. PVA was one ingredient, but by no means the entire solution.

[Richard J Kinch]

Doug Miller writes:

> No, not really. PVA was one ingredient, but by no means the entire
> solution.

Your usual useless comment.

You are entirely correct, the product is mostly water, not pure PVA, with a
bit of preservative. Which has nothing to do with the application.

Now tells how atoms are mostly empty space.