What is the best way to mount bowl blanks in my four-jaw chuck?
As a new woodturner, I'm looking for the best way to mount bowl blanks in my four-jaw chuck. I like the idea of using a recess rather than a tenon in the bowl bottom because the recess eliminates turning away a tenon as the last step to complete the bowl. But my chuck has dovetailed jaws, and I'm struggling with cutting perfectly matching dovetailed recesses with my bowl gouge. Can you help?
—Steve Jacobs, Sacramento, Calif.
The good news, Steve, is this angle doesn't have to match precisely. The most critical aspects of mounting a blank in a chuck are making sure the wood rests firmly against the face of the jaws rather than the base , and that the inside corner of the shoulder has a clean, crisp transition ["Good Fit," below]. A slightly rounded corner ["Poor Fit"] negates some of the chuck's grip.
Whether making a tenon or recessed socket, begin by cutting it with a shoulder at a right angle to the blank's flat bottom. Then, use a skew chisel or dovetail scraper, shown above, to back-cut at an angle similar to that of your jaws. If you don't already own a dovetail scraper—they sell for $25–$50 each—you can modify an old scraper to the desired shape at your grinder.
Still can't get the hang of cutting dovetailed tenons or sockets? Then leave them with right-angle shoulders ["Acceptable Fit"]. But when turning the project to shape, take lighter cuts than you would when gripping the blank with a dovetailed tenon or socket to help the jaws maintain a strong grip.