(EE because "making stuff" is part of engineering :P )

This has been annoying me since about 8PM.

I'm building a case for the night-vision tube using a couple of lengths=20
of PVC pipe. One 90mm dia. length holds the tube proper, and a 50mm-dia.=20
length serves as a spacer to keep the focal-plane distance (distance=20
from the lens to the input coupler) correct. There's a 90mm pipe cap on=20
either end -- one to hold the eyepiece, the other to hold the lens mount=20
and spacer.

What I need to do is knock a ~45mm hole in the front of one of the pipe=20
caps.

Problem 1: these are EXTREMELY thick pipe caps. The plastic walls are=20
about 15mm thick!

Problem 2: I don't have a hole-saw suitable for PVC (actually, I don't=20
have a hole-saw at all: the one in the toolbox has a broken setscrew so=20
the drill bit won't pass any motion onto the saw-blade).

I've tried using the hot-knife bit on an Antex GasCat, which sort-of=20
worked... apart from the fact that it filled my kitchen with acrid smoke=20
and I had to give up part-way through. Turning the heat down only served=20
to completely stop the PVC from melting. Lovely.

The Dremel won't work either -- the router bit gets clogged with bits of=20
PVC very, VERY quickly and just plain stops cutting. I suspect my PCB=20
router bit isn't geared up for uPVC, or the Dremel is moving too fast=20
and melting the plastic (not surprising).

Short of "buy a new holesaw" (apparently *not* stocked by the local=20
B&Q), does anyone have any ideas how I might be able to cut these holes?

Thanks,
--=20
Phil.
piclist@philpem.me.uk
http://www.philpem.me.uk/
--=20
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