In article ,
Doug White wrote:

I need to make some clear front sight apertures for my target rifle.
These have a conical hole bored in the center, which makes a small black
ring when mounted in a hooded sight tube. The commercial ones are
getting scarce, especially in the sizes I need. The OD is ~ 0.86", and
the inner hole will go down as small as 0.095"

I'd like to turn the OD on a short stack of blanks bolted to an arbor
with a 2-56 screw. If I can cut them into rough octagons, I should be
able to turn them to size fairly easily. What I'm wondering about is the
best way to cut out the rough blanks without raising a burr or making a
mess out of the protective plastic/paper film on the back side. I'd
planned on using my bandsaw, but my experience is that the back of
plastic cut on it is pretty rough.

I was thinking I could back up the plastic with scrap masonite to get a
cleaner cut. It might also be time to put a new blade on the saw. I
thought about sticking the plastic down with double stick, but I suspect
the protective film would come off when I try to remove the backer.

Any other tricks or suggestions?

Thanks!

Doug White

It's been quite a few years (I did a lot of round plexiglas things back
in my lab-rat days), but either a sharp holesaw or a flycutter, either
one run slow enough and/or with enough air to keep it cool to limit
chip-melting, might be worth a shot.

Then again, a coping saw or jewelers saw would let you control cut speed
to a fair thee well and might get the job done as well or better than
the bandsaw would. Generally backside roughness == melted and re-welded
chips.

For thin stock shears or tinsnips might work, nipping the corners off -
at some point (of thickness) they stop cutting and start shattering,
though.

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