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.
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.
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
: "Andrew Barss" wrote:
<I have had bad times trying to drill Lexan>>:
: Time to visit your local plastics distributor.
: They will have the tooling to handle plastics.
: Drill bits require special relief angles.
Thanks, Lew (& Larry, and the others downthread) -- very useful
tip, and I'll give it a go with these --
On Thu, 01 Sep 2011 23:36:15 +0000, Andrew Barss wrote:
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:
Intelligence is an experiment that failed - G. B. Shaw
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
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
This flat needs to be in line with the axis of the bit.
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.
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.
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