Holes in Plexiglass

[Rodney]

I am going to need to cut some different sized holes in some 1/4 plexiglass and wonder what others experience in this is. I have all types of hole saws that are primarily designed for wood. I have not found any other type hole saw. My concern is getting a clean cut hole. Any suggestions?

Thanks in advance!

[Trevor Hale]

I am going to need to cut some different sized holes in some 1/4 plexiglass and wonder what others experience in this is. I have all types of hole saws that are primarily designed for wood. I have not found any other type hole saw. My concern is getting a clean cut hole. Any suggestions?

Thanks in advance!

Honestly the best type of bits I have used to drill holes in Plexi are Masonry bits.

The duller the better, I have never tried a hole saw, but that should be fun. I would suggest testing on some practise peices first.

Trev

[Rodney]

Trev,
Thanks. I actually have a "backed off" drill bit made for plexiglass. The holes I'm speaking of are for gauges.

[Michael Carter]

Spade bits work very well in plexiglass. Though I've never seen one as large as 3".

[blueskydriver]

Rodney,

I drilled some different sized holes into plexi using both wood and metal, as well as hole cutting bits; you know, the type that are made for door knob hole cutting, but in various sizes. Don't use the variable hole cutter bit that has the adjustable cutter tip. That type of bit flexes ever so slightly, which is okay for wood, but will cause splintering in the plexi Additionally, I've used the wood spade bits that Michael has used without any problems.

My best advice is to use a drill press to drill the holes and start by drilling pilot holes first. The drill press should be set to a slower speed. Not to slow, but not fast either. Too slow will cause cracking and too fast causes melting of the plexi which will cause cracking as well.

However, before you start, place some masking or boxing tape on the plexi (before making you measuring marks) to absorb the initial contact of the bits to the surface and thereby, reducing the splintering which causes cracking to occurr.

Finally, place the plexi onto a piece of plywood (not press or chip board, but a good grade of plywood) that you don't mind wasting and then clamp it all down to the drill press work plate (the plate just below the bit). By the way, dont remove the protective covering until you're ready to use the plexi (the last step in whatever it is your making).

I hope this helps,

John

[AndyT]

Just to restate what John said:

Cover the area you are going to cut with masking tape first. It prevents many problems as you cut.

Cut slightly smaller than you need and sand back to your exact measurement. For plex, use a wet sandpaper and go slow with tape on BOTH sides. That will protect your surface as you cut and sand.

[Rodney]

Thanks Gentlemen. I will try with spade and hole saw bits on some scrap this weekend and let you know how it turns out.

[warvet]

Rodney,
I have cut tons of plexiglass and my experience is keep water on it where your cutting so heat doesn't build up and thats what causes it to crack. JMO

Tim

[Rodney]

Well I achieved the desired results using what others said here. Clamp to good plywood, use spade bit, light pressure and mask the hole before drilling. Because I am using a sheet 26" X 25" I could not use a drill press yet with the sheet clamped tight I had no issues. Now to get busy cutting some annunciator holes. Thanks to all of you!

[Michael Carter]

I was going to mention that if you're not using a drill press because the size of the piece, clamp it as close to the hole you are drilling as is possible.

When I have to drill on the bench, I use a backing piece then the plexi, and then another piece of plywood very close the the hole all clamped to the wood bench.

Those spade bits do cut a nice hole, especially for switches.