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.

---Works GREAT!!! ---Every time!!!

Pete Stanaitis
------------------

Heat distorts the flatness of the plastic. A forstner drill bit works better
and a sacrificial piece of wood under the plastic is always cheap insurance.
What problem.
Steve

"spaco" wrote in message
...
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.

---Works GREAT!!! ---Every time!!!

Pete Stanaitis
------------------

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.

I'd be using lexan in the first place.

Wes

"Wes" wrote in message
...
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.

I'd be using lexan in the first place.

Wes

Yep - since "discovering" lexan/polycarbonate I've not used acrylic for
much.

IIRC, the local Plexiglas shop has some drill bits intended for
Plexiglas. They look like high speed steel bits, but they have a smaller
tip angle (sharper point).

Backing the piece with a block of wood is still a good idea.

--
Paul Hovnanian
------------------------------------------------------------------
Karate is a form of martial arts in which people who have had
years and years of training can, using only their hands and feet,
make some of the worst movies in the history of the world.
-- Dave Barry

In article , says...

IIRC, the local Plexiglas shop has some drill bits intended for
Plexiglas. They look like high speed steel bits, but they have a smaller
tip angle (sharper point).

Backing the piece with a block of wood is still a good idea.


Having drilled hundreds of holes in Plexiglas over the years, this is the best
way. We used to resharpen our own bits to a much 'pointier' configuration. They
do not take a very big bite and are very controllable and do not grab as they
come through the back.

--
MacD

On 2008-12-15 14:30:11 -0800, spaco said:

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.

---Works GREAT!!! ---Every time!!!

Pete Stanaitis
------------------

I don't know how this would work for holes as big as yours or in the
thickness of the material you're using. For holes in the 1/8" realm,
in material about 1/8" thick, just run the drill fast and backwards.
The friction creates heat and the drill pokes right through in the time
you'd expect it to take to cut through if you were using the drill
properly.

--
=-=-=-=-=-=-=-=-=-=
Rob Skinner
La Habra, CA
www.rustyiron.com

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.

The right way to do this, particularly if tolerances are high, is to
use a drill bit ground specifically for acrylic and other plastics.
It has a much steeper tip angle, usually 90 degrees, zero rake, and is
kept razor sharp. You can get them at a plastics supplier for a few
bucks, or make them yourself if you can grind drill bits.

In article , woodworker88 wrote:
The right way to do this, particularly if tolerances are high, is to
use a drill bit ground specifically for acrylic and other plastics.
It has a much steeper tip angle, usually 90 degrees, zero rake, and is
kept razor sharp. You can get them at a plastics supplier for a few
bucks, or make them yourself if you can grind drill bits.

I use "slow twist" drill bits. I have a whole index full. They aren't
quite 90 degrees, but they are close enough that I've never had a
problem with a variety of "grabby" plastics.

The key thing to watch out for is heat. You either want as little as
possible, or lots, enough to throughly melt the stuff. In between, and
the plsstic swells into the hole, grabbing the bit, frequently with nasty
(and sometimes dangerous) results.

Doug White

On Mon, 15 Dec 2008 17:48:10 -0500, the infamous Steve Ackman
scrawled the following:

In , on Mon, 15 Dec 2008
16:30:11 -0600, spaco, wrote:

We'd have to drill many holes in 3'8" thick plexiglas, on-site,

Double take... triple take. Oh!!!! He meant 3/8"

Otherwise, that man needs transparent aluminum. Scotty will fix him up
with the formula.


I know I've drilled plexiglass, but it's been so
many years, I don't recall the trick. I *think* we
just put a block of wood under it.

Forstner bits work OK, but brad point billdrits are the best I've
found for plexi. Yes, back it up and hold it down on the backup
board!

--
It is pretty hard to tell what does bring happiness;
poverty and wealth have both failed.
-- Kin Hubbard

Woodworker has the only answer. Grind the cutting edge to 90 degrees
and the drill scrapes out the material. Super easy.
I've even done it on large drills for drilling cast iron when the
drill tries to screw itself through the material.
You get the gold star.

Doug White wrote:

The key thing to watch out for is heat. You either want as little as
possible, or lots, enough to throughly melt the stuff.
Doug White

Use some soapy water as a cutting fluid/coolant. And, Agreed, use a
pointy drill bit. I also would stone the "corners" where the shank meets
the point rounding them a little....more of a reamer finish.
RR

On Dec 19, 9:29*pm, Dan@ (Pirateer guy) wrote:
Woodworker has the only answer. Grind the cutting edge to 90 degrees
and the drill scrapes out the material. Super easy.
I've even done it on large drills for drilling cast iron when the
drill tries to screw itself through the material.
You get the gold star.

That's what he means by the zero rake. What he means by the 90 tip
angle is the included angle of the tip, instead of the 118 or 135 of a
regular jobber bit...

That's what he means by the zero rake. What he means by the 90 tip
angle is the included angle of the tip, instead of the 118 or 135 of a
regular jobber bit...


a 10 penny nail flatened on the end with a hammer and put a 90 degree
tip on it works fine, same as above, for plastic. Always drill an
oversize hole because the plastic will move around quite a bit with
tempature changes. The common thing to do is to drill a hole oversize
and put a piece of rubber hose on the screw that will go into the hole
and stick slightly outside of the plastic. The rubber is soft against
the plastic and also allows the plastic to move.


John