Cutting quarter-inch plastic (Saber/jig/scroll) saw

[Hoosierpopi]

One issue with cutting templates (for my router, etc.) out of plastic is the heat generated by the blade and the resulting melting (and, then fusing) of the material behind the cut.

I had a paper pattern spay-glued to the sheet of salvaged 3/16" plastic (from an old Staples Display Rack - great dumpster for "finds") and I tried spraying a lubricant ahead of the cut line. The paper pattern absorbed the oily/waxy spray and the cut material fell away leaving a clean cut behind. I had switched to a blade with fewer teeth (as I didn't have one of those plastic slicing blades on hand and thought reducing the number of teeth might do the trick before I thought of the oil spray).

THe stuff I used was foamy/waxy as opposed to the fine clear spray of a WD-40, say. I cannot say if WD-40 would have worked as well and cannot recall what the stuff I used was called. But The difference was so impressive that I thought to post it here FYI.

[Gerald Ross]

That is a keeper. If only we could find some of that foamy/waxy stuff. Now, where did I put that saber saw? I know I had one somewhere.

[Ray]

[Twayne]

I still use the score & snap method unless it's not straight lines. I never had much luck with jig-saws but my bandsaw with a fine-tooth design works well as long as you keep the speed of the feed constant and fast enough to avoid the heat buildup. For longish cuts, I'll sandwich the plexi between two pieces of 1/8" Luan and cut away. Another little trick on the table saw is to install a non-carbide blade backwards & make the feed rate fairly fast. Takes a little practice to get the feed speed right but it'll work well for long cuts. The main thing is to simply not allow the heat to build up durinig the cut. The Luan sandwich works best for that. For me, anyway. I don't know about WD-40, and had never considered anything like that, but cuttinng oil along the cut path might work well to pull heat away too. I'll have to play with that & see what happens.

Luck,

Twayne`

[BobF]

I have a "carborumdum wire" abrasive blade for my jigsaw, but it melts the plastic as well.

I use a foaming metal-cutting oil and it works quite well.

[Andrew Barss]

I've cut lexan and plexiglass fairly well on a TS, but what gets me is drilling the damn stuff. I built a tablesaw guard out of Lexan, and wanted to drill and tap the pieces together. No luck -- got several drill bits stuck, two broke off.

-- Andy Barss

[Lew Hodgett]

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Time to visit your local plastics distributor.

They will have the tooling to handle plastics.

Drill bits require special relief angles.

Lew

[Larry Blanchard]

I've had pretty good luck by sandwiching the plastic between two layers of plywood (or scrap wood). I used brad point bits at the lowest speed.

I've heard of these special bits but haven't used them:

[CW]

Negative rake on the drill bit and plenty of kerosene. Drills easily.

[Artemus]

It's the positive rake angle on standard metal cutting bits that is the culprit. It makes the bit want to dig in, and for steel that's good. A zero rake angle is needed for plastic to keep it from digging in. A drill bit made for brass has the needed zero angle. You can modify a standard metal bit by grinding a small flat, 1/16" is sufficient, on the inside (in the flute) of the cutting edge. This flat needs to be in line with the axis of the bit. Art

[Morgans]

"CW" wrote

Negative rake on the drill bit and plenty of kerosene. Drills easily.

What he said. You can modify a regular bit with a dremmel with a cut-off wheel. It only needs to be a couple degrees negative, which you can do by grinding the leading edge of the cutting edge straight up and down, or a couple degrees backwards from what the angle is now.

-- Jim in NC

[Andrew Barss]

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: Time to visit your local plastics distributor.

: They will have the tooling to handle plastics.

: Drill bits require special relief angles.

: Lew

Thanks, Lew (& Larry, and the others downthread) -- very useful tip, and I'll give it a go with these --

Andy Barss

[Doug White]

"Artemus" wrote in news:j3p8je$r1u$ [e-mail]:

They aren't true zero-rake, but you can buy "slow twist" drill bits that come close. They are available in a much wider range of sizes than the special "plastic" drill bits. They work very nicely on all plastics, as well as brass. Mcmaster Carr sells them.

Doug White

[kaylward]

If anyone is nearby in the Maryland area, I'd be glad to make some custom plexiglass patterns for them with my Laser engraver. It is capable of anything up to 24"x18", and I can create whatever shape you may need. Feel free to contact me to work out the details. Kevin