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I'm building a router bit box to store all my router bits of various sizes (¼ and ½). I want to have a see-through closing lid. In order to do so, I will frame a sheet of Plexiglas (1/8" thick) in wood. I couldn't find a sheet with dimensions close to what I need, so I bought a bigger one. I now need to cut it to length. I wonder how should I do it on a table saw. I don't need a perfect cut. All four edges will be hidden by the wood frame.

I've searched a bit online and people are suggesting a high teeth count blade. I'm thinking of using a cheap circular saw blade of 7¼" with 100 teeth or so. Will that give me an appropriate cut?

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Although you do want a high tooth count for a higher-quality cut, an ultra-high tooth count can be detrimental. With a 100T 7-1/4" blade, you'll have to cut more slowly and may burn the plastic.

If using a 7-1/4" circular saw blade, use a high-quality 50-60 tooth blade, which will perform similarly to the 10" 80T blade that Aloysius Defenestrate's local plastics company recommended.

To help protect against chipout at the edges, you can either tape the cut line or you can sandwich your Plexiglas between two thin pieces of sacrificial plywood or MDF.

Assuming your plastic is, indeed, Plexiglas (acrylic), you can polish the edges with a torch. Do NOT use a torch on the edges of Lexan (polycarbonate), because you'll just melt it. If you aren't sure which type of plastic you have, acrylic is bright when you look directly at the edge, while polycarbonate is dark when you look directly at the edge.

  • If you go this route, definitely use the sacrificial wood to sandwich it. The 1/8" is so thin that it will "bounce" in the gap between the blade and the insert causing a really poor edge and possibly cracking of the sheet outside the cut area. At least that's been my experience. – Colin Young May 22 '15 at 17:33
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Plexiglass works well with a craft knife too. If you score it a couple of times with a straight rule, it should snap cleanly along the break.

  • Yea, this would be infinitely less mess and is the typical way to cut plexi-glass. What I do is give it a good score (2 or 3 swipes with the knife), then I clamp the side I'm breaking between some 1x1 stock (to act a a press break) then put the score just over the edge of the workbench and snap down. It usually breaks cleanly. – DA. May 22 '15 at 16:02
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    +1 Using a tablesaw for this is overkill, messy, and may gum up your blade if the plexi melts. An acryllic scoring tool costs only a few dollars (or euros, or whatever) and can produce great results. – Gretchen May 22 '15 at 18:00
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The people at my local plastics place would say yes. (Their specific suggestion was 10", 80T.) They also said feed fast, though not so fast as to be unsafe.

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If you bought the Plexiglas at a brick-and-mortar home improvement store, most will cut the material for you for free, or for at most a nominal fee.

Our neighborhood Lowe's has a score-and-break rig all set up for this purpose.

  • True, but getting someone else to do it sort of defeats the purpose of this site :) – Steven May 22 '15 at 18:59
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    <nitpick>It's called Woodworking.SE, not Plexiglasworking.SE.</nitpick> Point taken. :-) Still, it points toward doing it the @slartibartfast way. – hBy2Py May 22 '15 at 19:20
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Just to add in at least a little something. It is possible to have the best of both worlds of Rob's answer and slartibartfast's.

At less risk of tear out and flying shards you can use the table saw at an angle in the area of 45 degrees to score the material. How deep you go would obviously depend on the thickness of your stock but you don't need much when you are scoring.

You still might need to have a board there to help move the piece allow the blade and something like a push stick would still be recommended. With a good fence this makes it easier to do a straight line (assuming you are terrible scoring other-wise.)

This would also reduce the risk of damage due to heat to the material.

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There are two basic types of plexiglass - extruded/rolled and cast.

The cast plexi cuts like a dream. Extruded/rolled plexi (which is what you get from a big box store) can be quite brittle and difficult to cut without shattering the edge.

I would recommend making a shallow cut less than half the thickness of the plexi on one side, then flipping it and doing the other, the breaking it along the cut and cleaning up the edge with a knife or file.

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