How to cut 1/4" plexiglass??

StephenT · Nov 8, 2015

I've got a 12"x12" piece of 1/4" thick translucent plexiglass. I need to cut out a piece about 4"x 4" to use in pre-flashing exposures. I intend to simply hold the piece in front of the lens and give shots a pre-exposure of about Zone II where necessary. I've been re-reading my Ansel Adams books!

I have never cut plexiglass, and 1/4" seems a bit on the thick side to try to cut like a sheet of glass (scribing and bending).

I have available a tile saw, a table saw, and a band saw. And of course, a hack saw, which I would prefer not to have to use!

Looking for recommendations from your experiences, please.

DannL. · Nov 8, 2015

Here's how I cut plexiglass. It works for me. If you have some to practice on, that is best. I use a hand-held power jig-saw with a fine toothed blade. I tape both sides of the plexiglass, the area where the cut will be, with old fashioned masking-tape (remember, both sides). I draw my cut-line with a sharpie on that tape. And then cut it with the jig saw. Without the tape, the plexiglass will melt, and your saw blade will get caught in the melted plexiglass. And that is not fun.

Note: if your blade feels as though it is beginning to bind, it simply means that the blade is getting too hot. You may need a slightly bigger toothed blade, or slow down to prevent heat from building up within the blade. Take your time, and don't force it.

Sirius Glass · Nov 8, 2015

Plexiglass will not cut like glass; scribing and bending will not work.

The side of the plexiglass that will have the saw on it must be covered with paper or tape so that it will not be scratched or marred. It is even better if both sides of the plexiglass are covered before cutting.

StephenT · Nov 8, 2015

Many thanks for the info folks.

silveror0: Thanks for the link. I've found the Rosco filters on Amazon - do you use the two stop one? Meter the scene, preexpose with the ND/plexi combo, then expose for the metered time without the ND/plexi? My plexi has 57% transmission, so would the two stop ND with the plexi give me the three stops from Zone V to the Zone II preexposure?

trythis · Nov 8, 2015

Table saw with high number if teeth. Jig saw with tape over the plastic

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Mark Fisher · Nov 8, 2015

I've used a table saw and a band saw. Leave the liners on the plex. Taping won't help a lot in my experience. A table saw with a regular wood blade will chip the edges. There are plexiglass blades, though. My choice would be a band saw with a cross cut blade (reasonably fine tooth). The problem on the band saw is melting so you need to keep it moving through the blade reasonably quickly. The best answer is to just go to the glass place or hardware store and have them cut it.

Photo Engineer · Nov 8, 2015

I use a Home Depot plexiglass cutter. Works just like a glass cutter but scores about 5x deeper.

PE

gone · Nov 9, 2015

I use the same technique as PE, but w/ a box cutter sort of knife. It's necessary to have a deep cut. You can scribe plexi and snap it off just like glass, but it helps to hold a piece of wood on the top where the scribe line is, hold or clamp it down firmly, and carefully align the bottom of the scribe line of the plexi w/ the edge of your table. It will snap off cleanly then.

If you don't have a clamp for the top piece of wood, you almost have to have someone hold it down while you use both hands to grasp both ends of your plexi when you snap it down. This technique won't work w/ 1/4" plexi if you have a cut near the egde though. In that case, it will have to be cut w/ a saw.

StephenT · Nov 9, 2015

silveror0: VERY helpful. Thanks!!

paul ron · Nov 9, 2015

plexiglass is cut by score n snap method. using a saw will actually melt the plastic at the saw kerf using a jig saw or sabre saw. band saw is better because it cuts cooler.

I've cut plexi on a 12" table saw but you risk a very serious kickback if you aren't experienced on the tool or the tool is not properly aligned with the fence.

now be aware we are not talking about polycarbonate (lexan). polycarbonate is cut on a table saw like wood. scoring n snap will just be imposable because it's much more flexable n will cold bend.

StephenT · Nov 9, 2015

Thanks everybody for the input. I've learned a lot about this stuff and how to cut it and how not to cut it!

Not having a plywood blade on the table saw, and having a seriously out of date jig saw (50+ years), I got to thinking. What blades do I have with my oscillating tools? I remembered that I had a semi-circular one that I assumed was for drywall (which I always cut by hand). That blade has lots of tiny teeth and has printed on it that it is for thin wood and plastics. Ah ha!

I gave it a try, using all the precautions I learned from the above posts, and voila! It cut great, no melting (used on about medium speed, using several passes on thin cuts), and the corners were smoothed with a bench grinder's fine stone on slow speed. Looks great.

It's certainly not a method that I would use for production speed cuts, but to cut out a 4" x 6" piece, it worked just fine. I hope my experience will be useful to those reading this thread, and again, my thanks for all of your input.

Vaughn · Nov 9, 2015

Photo Engineer said:
I use a Home Depot plexiglass cutter. Works just like a glass cutter but scores about 5x deeper. PE

Same method here...

M Carter · Nov 9, 2015

Jeez, there's a way easier way to do this… take, say a 2" long piece of PVC pipe, and a 2" connector. Cut a circle of matte mylar the same size as the pipe outer diameter, and use the pipe connector to hold it in. Spray the thing black, and you can hold it over the lens so there's no big wash of light. You can even drop a 52mm filter in it. (Unless I'm missing something, but I had all the stuff in the garage and it works like a champ).

Jim Jones · Nov 9, 2015

I've used a table saw with a sharp fine-tooth blade for cutting thick Plexiglass. A sharp blade cuts; a dull blade heats up the Plexiglass.

paul ron · Nov 9, 2015

to finish the edges... flame polish it with a propane torch. it'll look like glass.

OzJohn · Nov 10, 2015

There's nothing special about Plexiglas - it's just one of a number of trade names for acrylic. It is also not that difficult to cut with the right tools. Contrary to what some others have said, it can be cut well either by scoring or using a circular saw/table saw. Many picture framers score and break it on the same device that they use to cut glass - a wall mounted glass cutter. I don't think I'd try to score and break 1/4 inch thick acrylic though - for that I'd use a circular saw and a blade with triple ground teeth. There are blades especially made for cutting plastic but a good compromise can be one with lots of teeth that is designed to cut soft metals. Don't expect to make a clean cut in plastic with any blade designed for timber nor some old blade that has been kicking around on the saw for years. The blade needs to be super sharp for plastic. OzJohn

How to cut 1/4" plexiglass??

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