A hole saw is a tubular tool with teeth filed on the lower end of the tube. The teeth have a set to cut a groove wider than the thickness of the tool wall. A shaft is fastened to the top of the tube so that it can be mounted in a drill press to drive the saw. Usually a pilot drill and guide are provided to locate and center the hole saw. Knockout holes are located in the top of the saw to allow removal of the discs. Hole saws are stocked in sizes from 5/16" to 4" diameter. Large diameter hole saws may be made by inserting a piece of band saw blade in a groove machined in a steel disc and holding it with set screws. Coarse tooth saws should be used for cutting Vical acrylic.

The Vical acrylic should be cut half way through, turned over, and the finishing cut made from the other side. When cutting Vical acrylic greater than ¼" thick, a detergent­water lubricant and coolant should be used.

ROUTERS

Portable and overarm routers are used for trimming the edges of flat or formed parts, particularly when the part is too large or awkward to use a band saw or stationary router.

Routers should have a minimum no­load spindle speed of 10,000 rpm. Two­flute straight cutters less than 1 ½" in diameter will produce the smoothest cut at this speed. Cutters should be kept sharp and should have a back clearance angle of approximately 10 degrees and a positive rake angle of 15 to 30 degrees. Jigs should be provided to guide the router.

Cutting  Vical Sheet