Q: I need to drill a 2-inch-diameter hole through a sheet of ¾-inch Lexan. Do you have any suggestions about how to do this?

— Alan, Pine Brook, NJ

A: Tom Silva replies: Lexan is a polycarbonate plastic with high-impact strength and unusual clarity, which make it useful for security glazing, power-tool guards, and the like. But drilling holes larger than an inch into Lexan dramatically reduces its strength. If that's not a problem on your project, here's how to do it.

The basic strategy in drilling into any plastic is to use a sharp twist bit at a slow speed to minimize heat. (If the bit creates shavings, the speed is okay. If it's gumming up, let it cool, then go slower.)

A 2-inch hole calls for something bigger than a twist bit; I'd use a hole saw with carbide teeth—not just carbide grit. You could easily spend $70 for such a tool—look for it in supply houses that cater to tile setters, countertop fabricators, or plumbers—so it might be cheaper to have someone from those trades drill the hole for you.

If you do tackle the job yourself, run the hole saw at a slow speed and clamp the plastic to a benchtop so it won't spin like a propeller if the saw binds.
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