Cutting Polycarbonate for Offset Router Base
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| Posted in Jigs, Fixtures, Tips & Tricks on
I would like to make some offset bases for my fixed base routers using 1/4″ thick polycarbonate. Can this material be safely cut on a tablesaw? If so, what type of sawblade is best?
Also, is it safe to trim this material with a router? If so, what type of bit works best?
Any other suggestions would be appreciated.
Replies
Yes, a cross cut blade with high tooth count such as 80 tooth blade will do fine and a trim bit will work. A slow steady cut without stopping to prevent the plastic from melting.
They make special drill bits to drill plastics cleanly. Check with a company that sells plastic fabrications.
One more tip- drill bits intended for metal can dig in to polycarbonate aggressively resulting in very bad holes. A drill press with stops and the piece well clamped down will result in better cutting, especially where you are making non-through holes or counter-boring for screw heads.
TBH Polycarbonate looks nice but I've never found it better as a router base than MDF which is far easier to work and cheaper.
Setting your blade height so that it just cuts through by only 1/8" or so will cause the teeth to cut at a shallow angle, keep more teeth in contact, and result in a smoother cut. I have an old "plywood" blade, not carbide with about 100 teeth, and it works great.
Just take light passes with the router. However, I rarely bother. I just use a sanding block. I'm usually not looking for a polished edge.
One more suggestion...there are lots of different type of clear plastic that will work for this purpose...buy the "scratch, uv and impact resistant" variety --McMaster Carr has all sizes and specs. Also, McMaster sells drill bits that are designed especially for this material (drilling with Brad Points or twist gave me fits) and a match-size piloted countersink is a huge help for those holes when mounting the new offset plate to your router. (1/4" polycarbonate cutting bit is item #27465A84 and through-hole piloted countersink #2739A64)
One more thing...yes you can route polycarbonate, but it is very fussy! Make sure you take very light passes...if the bits flutes clog (melting plastic doesn't help this) it can grab and want to kick back. Light, light cuts...no more that a light 1/16". Makes a wicked mess. The little plastic shavings seem to have a static charge and stick to everything.
Excellent suggestions from everyone who responded. I now have a clear path forward and know what pitfalls I can avoid with the right drill bits, router technique, etc. Thanks to all who responded!
I have no experience with routing plastic. But for drilling, it really works better if you modify a regular drill bit to give it a slight negative rake on the cutting edges. You can do this either with a small sharpening stone with the drill stationary, or you can bring the drill to a larger stone (or grinder). On each cutting edge, just make a small flat that is either parallel to the main axis of the drill, or (better) leans slightly back, away from the direction of the cutting motion. By small I mean with a width of 1/32 inch or less; it doesn't take long. Do it on both cutting flutes, trying to get them similar in size and angle.
With such a drill at moderate speed you'll find that you get twisty chips rising out of the plastic as you cut, and the drill will cut smoothly and won't grab or crack the plastic. A modified drill like this also works great in brass. (Vic Tesolin didn't mention this in his article on making brass hardware in FWW a year or so ago, but he did complain that regular drills could be "grabby", which is true.)
Tablesaw blades made for plastic also have this slight negative rake on the teeth. They work great.
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