How To Cut Plexiglas?

A

Allan

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Fellow Metalheads.
I need to cut some 6-7" diameter plexiglas discs 1/8" thick. What is the best way to do so without them chipping, cracking or otherwise mutilating them? Not sure if they are Lexan or Arcrylic or whatever. I was going to use my adjustable, one legged cutting tool that is a ground bar 5/16" or so square. It goes into the drill press. Can't remember the correct name for it. Lee Valley calls it a "Wheel and Circle Cutter". It is really a wood working tool. I have used it in the past to cut thin brass circles by turning the tool by hand so that it doesn't grab. Would that work here? What has worked best for you? Looking forward the many approaches to this.

Al
 
hi Alan
I'd mark your shape with a permanent marker (in the uk a staedtler felt tip) and use as fine a tooth band saw blade that you have.
1/8 inch is thin so you could back it up with a thin sheet of plywood to support the sheet and stop it shattering the sheet
the problem with plexiglas and other acrylic sheet is that they have a low melting point and gum up tools very quickly so a dremel is out of the question to cut it out. Once you've roughed out the shape, sand against a sanding belt or wheel and slowly sand to the line. Once done leave a few seconds for the plastic to harden, turn over the disc and peel back the flash and it will fall off.
If you don't own a sanding disc take the roughed out disc and with a dremel and a sanding mandrel mounted grind to the line. but please use safety glasses the shavings are very very painful if you get them in your eyes.
Graham
 
Plexiglas (Acrylic) is nasty stuff to work with. It chips easily, expands a lot when heated, has a low melting point, and low thermal conductivity. I avoid it when possible. Lexan (polycarbonate) on the other hand is tough, strong, and machines beautifully. For what you are doing, you are probably going to have it pretty easy because the material is thin. The tool you describe sounds like a trepanning cutter, and it should be just the ticket. I would recommend a tool with no back rake, or negative back rake, kind of like you would use for brass or cast iron. Depending on the accuracy you need on the outside, I might go halfway through, flip it over, then finish it, so you have cleaner edges. Mainly that last part applies if it really is acrylic. If it's lexan, just go straight through.

I would also recommend clamping the sheet to the table... both materials are SHARP, and you don't want them to helicopter. Also, run a deburring tool over them once cut, as I have cut myself numerous times on the stuff ;)
 
Thank you all. I bought a sheet at the local harware emporium from a rack of various sizes and no labels. I guess the safe thing to do is treat it like arcrylic and all should go well.
Al
 
if you want to now what material you got
look at the sidecut plexy is white transparant and lexan is blue
plexy is a pain to work with (like mentiont in a previus posts )
lexan is way better but way more expencive if you need to buy it
they make bulletproof stuff out of lexan

if you want to cut plexy wit a bandsaw ore simular powertools do not cut o fast it melts very quick
and use some wd 40 ore other fine lube to spray nearly continius on the blade so the cut is greacy
and the two halfs you just cut tru do not melt back together
i also do the same for lexan it gives a better finish cut
on a strait cut i use a wood planer to debur
 
Allan said:
Fellow Metalheads.
I need to cut some 6-7" diameter plexiglas discs 1/8" thick. What is the best way to do so without them chipping, cracking or otherwise mutilating them? Not sure if they are Lexan or Arcrylic or whatever. I was going to use my adjustable, one legged cutting tool that is a ground bar 5/16" or so square. It goes into the drill press. Can't remember the correct name for it. Lee Valley calls it a "Wheel and Circle Cutter". It is really a wood working tool. I have used it in the past to cut thin brass circles by turning the tool by hand so that it doesn't grab. Would that work here? What has worked best for you? Looking forward the many approaches to this.

Al
Click to expand...

the best way is to cut them out on the band saw with a 1/8 or better left on the diameter. Next make two pieces of plywood out the diameter you want to finish the plexiglass or lexan to with the bandsaw. Make a center drill hole in one of the plywood pieces for the tail stock center to support. Take them to the lathe and using the 2 pieces of plywood cut to the diameter sandwich the plexiglass. Press together between the chuck or faceplate with the tail stock center. Turn the plexiglass/lexan to the diameter.

cliff
 
If you can clamp it a hole saw without the center drill and slow speed, but will be some burning at the edge a lube of water with soap might help.

Or a fly cutter used it wood but don't remember if they go that large also a Router would do it with a Circle jig.


Jeff
 
Allan said:
Fellow Metalheads.
I need to cut some 6-7" diameter plexiglas discs 1/8" thick. What is the best way to do so without them chipping, cracking or otherwise mutilating them? Not sure if they are Lexan or Arcrylic or whatever. I was going to use my adjustable, one legged cutting tool that is a ground bar 5/16" or so square. It goes into the drill press. Can't remember the correct name for it. Lee Valley calls it a "Wheel and Circle Cutter". It is really a wood working tool. I have used it in the past to cut thin brass circles by turning the tool by hand so that it doesn't grab. Would that work here? What has worked best for you? Looking forward the many approaches to this.

Al
Click to expand...


I'm sorry Al, I missed that you needed discs in my prior response (which I will delete since it is inapplicable).

I use a circle cutting tool in a drill press (or mounted on a hand held power drill if the sheet is too large for a drill press).

It's adjustable for any diameter up to 12" and the bit on the end cuts through plastic like butter.
Two caveats- you will get a phenolic smell so don't inhale or wear a mask, and you will get some plastic "swarf".

I am looking for a photo of the tool as I type this. Here it is.

Sears-25293-Circle-Cutter-300x3001.jpg

Sears-25293-Circle-Cutter-300x3001.jpg
 

WARNING!

Cutting acrylic with power tools is very risky business because it has a low melting point and has a tendency to weld itself to the tool when you least expect it. If you are holding the part when that happens, get ready for a world of hurt. I once saw a guy nearly lose his thumb sawing plexiglass sheet on a table saw. The blade grabbed the sheet and kicked it back, taking his hand with it. It wasn't pretty. Drilling, sawing (except bandsawing) and trepanning all fall into this risky category. I always choose polycarbonate over acrylic because it's much easier and safer to use. An option to consider if it has to be acrylic is to cut the stuff by scoring (both sides), then finish the edge. I never tried it on a circle, but it works great on straight cuts.

Tom
 
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