Cutting Clear Acrylic

Advice on blades, bits, and procedures for cutting sheet acrylic. January 12, 2009

I'm guessing there are plenty of you using plexiglas in various architectural projects. We're faced with cutting 40 - 11 x 14 pieces from 4' x 8' sheets. We'd like to machine-cut these and can use a table saw and/or a vertical panel saw. We have a few triple chip blades around we used for solid surface cutting at one time. So I'm wondering how to cut with the least aggravation and the most consistency. Any thoughts?

Forum Responses
(Architectural Woodworking Forum)
From contributor P:
We use a Freud rip blade for all plex cutting above 3/8" thick. It doesn't melt the edge of the plex, probably because of the fewer teeth = less friction. We regularly cut up to 1" thick with that blade, both on our table saw and panel saw.

From contributor D:
Don't try cutting them on a miter saw.

From contributor R:
I think you have the plan. I use a triple chip, no problem. If there are any good techniques on cutting, they are:
Use a sharp one.

Use a zero clearance insert.
Don't cut slowly (can lead to melting of edge), cut at same speed you would on a sheet of ply.

From contributor K:
A friend of mine runs a CNC router and we just happened to be talking about cutting plexi and what he was told and applied to his cutting practices, was there are (at least) two types of plexi - extruded and cast. The plexi with the paper covering is extruded and machines far better than the cast, which has the thin blue plastic film over the sheet. Questions to an industrial plastics supply house might also provide info.

From contributor S:
The masking has nothing to due with the type of plexi under it. Cast plexi cuts and machines better than extruded, but the cast costs more. Use the triple chip blades to cut, and try Onsrud "O" flute bits for routering and machining. If you are cutting on the saw and don't like the edge finish, leave the parts a hair big and take a light pass over the jointer.

From contributor C:
10" 80 tooth TCG. Have been cutting plexi for 30 years with that setup. Cut like you would any other material on the table saw. I can hold a +/- tolerance of less than .010" and achieve an acceptable finish on the table saw. If you need a machined edge, cut a bit over and clean up on the router table with a carbide spiral bit. Stay away from the film masked acrylic window glazing that they sell at places like HD. It is a little softer and does have a tendency to melt a bit and the masking is horrible to work with. Do yourself a favor and pay the extra for the paper masked material. The paper will stay on for all the fabrication you could possibly do with acrylic. Not so with the cheaper film masked material.

From contributor L:
We've gotten away from cutting plastics on a saw, especially acrylics. Any little chip can lead to later cracking. Much better to cut on a CNC with an Onsrud "O" flute bit. Unless someone is really into cheap, we try to use a more durable plastic - PETG or polycarbonate. Neither seems nearly as subject to cracking and both can be cold formed to a surprising extent. If we have to use acrylic we will order the cast. Going to CNC cutting allows us to cut in pulls and notches that used to be either bonded on or had problems with finished inside corners from jig routing. We just heat the pulls and turn them up. Never had a failure, as opposed to the bonded on ones. We are now doing a chain of grocery stores because the plastic fabricator before us had so many failures with cracking and pull bond failure. And we are higher priced but cheaper in the long run for the vendor. (It took a free sample and letting them abuse it for awhile to get the job.)