On Dec 15, 5:30*pm, spaco wrote:
We had a job recently to install plexiglas shields over a forged steel
gate/railing to keep people from reaching through the ballisters and
unlocking the gate. * We'd have to drill many holes in 3'8" thick
plexiglas, on-site, to mount the several pieces that had been
professionally precut to various shapes. *Not a good place to fail.
* *Having had some bad previous experiences cracking the plexiglas when
the drill breaks through, I convinced the boss to stop by a glass shop
on the way to the job and ask them how to prevent problems.

S000000000 simple! *When I asked the guy, and used the word "drill", he
said no no no. * Juat take the size drill you need, heat the SHANK end
with a propane torch and push that end *through. * As the drill melts
its way through, it leaves a little hump of melted and resolidified
material at the edge of the hole. *Just take a razor blade and carve it off.

Pracitce one or two holes first, to get the feel of the drill bit
wanting to slide as it makes the puddle.

A plexiglass drill works great too... especially after you get to
holes where the hole size is bigger than the plexiglass thickness.
What happens if the hole is bigger than the plexiglass thickness and
you try to melt your way through, is that you distort the plastic.

And a recommendation: polycarbonate is the most wonderful step up from
plexiglass for machineability. It never cracks like plexiglass wants
to.

All the news reports badmouth biphenols, but polycarbonate is an
amazingly versatile material. More expensive than plexiglass, but such
a joy to machine.

Tim.