Use a drill first. Drill all the way. Then use a round file
to file out the plastic into circle.... Not pretty but it will work
well. You will need a round file and half round ring file.

John



--- On Fri, 2/11/11, Philip Pemberton <piclist@philpem.me.uk> wrote:

> From: Philip Pemberton <piclist@philpem.me.uk>
> Subject: [EE] Cutting holes in thick uPVC pipe caps
> To: "Microcontroller discussion list - Public." <piclist@mit.edu>
> Date: Friday, February 11, 2011, 6:36 AM
> (EE because "making stuff" is part of
> engineering :P )
>=20
> This has been annoying me since about 8PM.
>=20
> 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.
>=20
> What I need to do is knock a ~45mm hole in the front of one
> of the pipe=20
> caps.
>=20
> Problem 1: these are EXTREMELY thick pipe caps. The plastic
> walls are=20
> about 15mm thick!
>=20
> 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).
>=20
> 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.
>=20
> 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).
>=20
> 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?
>=20
> Thanks,
> --=20
> Phil.
> piclist@philpem.me.uk
> http://www.philpem.me.uk/
> --=20
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>=20


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