What's the best way to cut acrylics and plastics?
I've been asked to make several wood-frame display cases with acrylic (Plexiglas) panels. The acrylic I purchased comes in large sheets. What's the best way to cut it down to size?
—Richard Barerra, Little Rock, Ark.
Cutting acrylic or other plastics (such as polycarbonate and phenolic) isn't a whole lot different than cutting wood, Richard. In fact, you use many of the same tools. However, follow a few finer points for best results.
A tablesaw is the most efficient tool for cutting sheets of acrylic down to size. Most manufacturers offer blades made specifically for cutting acrylic and plastics, so if you'll be working with these materials on a regular basis, you may want to invest in a dedicated blade. For occasional use, however, an 80-tooth, triple-chip-grind (TCG) blade for cutting laminate or plywood works fine. Even a 60- or 80-tooth alternate-top-bevel (ATB) crosscut blade will get the job done (although you may experience some chipping).
Equipped with an appropriate blade, next consider your feed rate. If you feed the acrylic into the blade too quickly, you may experience chipping. Feed it too slowly and friction from the blade may melt the acrylic, resulting in a poor-quality cut. Finding the right feed rate requires a bit of trial and error, but in general, use a slightly slower feed rate than you normally do when cutting wood.
Thin (less than 1⁄8 "-thick) pieces of plastic can vibrate or bounce up and down on the saw table as you cut. Counteract this by sandwiching the plastic between two pieces of plywood or hardboard.
For curved cuts, use a bandsaw. To minimize chipping, match the bandsaw blade to the thickness of the plastic you're cutting. For cutting 1⁄4 " or thinner acrylic, use a 10–14-tpi (teeth per inch) blade. With thicker plastics, a 6–8-tpi blade works well.
Remove saw-blade marks by filing or scraping, and then sanding with progressively finer grits. Or as an alternative, cut pieces slightly oversize initally, then use a template to bring the piece to final size and create smooth edges, shown below.