|Tip: Plastic Decking for Vacuum Chuck|
Plastic Decking for a Vacuum Chuck
I use threaded plastic decking planks and plastic pipe for my airtight vacuum chucks. Other turners have used MDF and then coated the threads with CA glue and coated the edges and flat surfaces with shellac or varnish in an attempt to achieve an airtight seal, with varying degrees of success. Plastic decking is already airtight and holds threads well, is durable, readily available (scraps at construction sites are usually free), and easily shaped with woodworking tools.
Mark out the blanks about ½" (13mm) oversized, cut them out with a bandsaw, drill a hole in the center, and tap with a wood tap the appropriate size for your lathe. Then screw the blank onto the lathe headstock, turn the blank round, and true up any wobble. Next, measure the inside of the piece of plastic pipe you are using for a chuck and carefully turn a friction fit rabbet on the edge of the blank. Use silicone adhesive sealant to glue the pipe to the blank. After the sealant has cured, true up the pipe on the lathe and glue ethylene plastic foam (used for packing) to the edge with 3M Super 77 spray adhesive. The thickness of the foam doesn’t matter. I have used 1⁄16"–¼" (2mm–6mm) thick with equal success.
An alternate method is to mount the blanks between centers and turn a tenon for a four-jaw chuck. Mount into the four-jaw chuck, drill and tap on the lathe, and then screw onto the headstock threads. Proceed as for the first method.
~ Doug Turner