Cutting Plexiglass

[RevD]

I am reading through the excellent construction manual that Ron did on the Express. I'm about to start a long build on a Express-esque amp. On page 71 there was something about cutting plexiglass to use as a template for the holes to be drilled in the bottom to bolt down the chassis into the nut inserts on the chassis bottom.

There was some question of squareness you'd get cutting plexi and while I'm sure you could get closer with a table saw and the right blade (which I don't own, hence using this method which I'll use in probably conjunction with the drawer cabinet method for a head cabinet), I thought I'd pass my experience along on 'cutting' the plexi using another method. Now I must say I didn't put a square up to my edges so take it with a grain of salt, but I believe they'd be close enough for government work as they say.

I've cut plexi a number of times to use as amp faceplates (like I'm sure hundreds have here) and I found a tool usually sold in like Homedepot where I got mine right near the plexi bins. Basically with plexi (and I'm talking Plexi only and not other scratch resistent polycarbonites) you cut it like glass. The tool is just a flat dull blade you scrape along the cut line to make a score, a small common screwdriver, awl or probably any number of other things could be used.

As I say, like cutting glass you score an edge. Put it on the edge of a sharp table and with the scored side up you snap it right at the edge of the table. The scored edge then breaks right at the score. Longer cuts can be a chore, but if you get the break started it will usually (or should I say often heh) run the full length if your score is deep enough. To smooth the edge I normally just take a xacto knife and scrape the edge across to take off any burs that remain.

I always buy a bit more than I need, just as glass, plexi has a mind of its own and will sometimes crack in a way you don't want it to. This worked on like 1/8" plexi, thinner, you might just use a xacto knife and continue scoring several times until you go through the stuff, not that it would'nt snap, but its so thin I don't think I'd bother.

I think you'll also find that drilling it with brad points or a uni-bit will do much better for you that trying to use a twist bit. Twist bits tend to make it crack while drilling. On thicker plexi I'm told if you run a flame alone the edge like using a torch it'll smooth the edge, I've not tried this on thinner plexi so I can't comment on it. You can also btw use a dremel to make a hole, although it tends to melt a hole more than cut it, it does work though.

All of this may will have been posted before, and perhaps better, but I thought I'd throw this out here, be nice if it's been discussed to death!

Regards,

Don

[Big Jim]

I use to work in the glass business in my previous life, and Don it sounds like you have done your homework. Good post.

[RevD]

Thanks Jim, I worked in warehousing, did some welding on firedoor frames and doors. We used to cut glass as well for the security windows. Typically clear wire plate. I noted plastic cuts very similar. Thanks for the post.

Regards,

Don

[backpack]

Drying it out cuts down on the cracks. But the static will knock your socks off after a sheet has been a drier for two or three days. A decent sign shop should have one and should be glad to do it for you.

[Gaz]

FWIW, I cut mine (and garolite) with a small wet tile saw. Wouldn't do it any other way.

[Cantplay]

I used to fabricate in plexi making electrophoresis tanks. Cutting, glueing and various machining operations.

You need an extremely sharp blade, and it helps if you have an airgun setup to blow the chips away as they will try to stick.

Leave the paper on as long as possible.

Regular twist drills work well, but they must be HSS name brand, not Chinese or Indian. You can not push the drill at all, you have to let it cut, and raise it frequently to clear chips. If the chips are allowed to build they will rub and heat crack the hole.

For milling we use a water soluable coolant in a mist gun.

John

John

[Bob S]

It's been 40 years since I worked with plexiglass & my memory isn't great.
But...
For gluing plexiglass chloroform works best.
Obviously you have to be careful using it.
Specially if you don't want to fall asleep.
Cutting tools want to snatch at it.
Drill larger holes in small incremental steps.
Or use a good sharp high speed hole saw..
John's right - only use good sharp tools.
And order more material than you need.
This much I remember.