From the Archives
Here is a handy machining trick for quickly truing any thin disk- or washer-like shape in the lathe chuck. I have used it many times, and like many good tricks it is simple and quick. I am sure thousands know about it, but other thousands probably do not.
Lightly mount the disk in the chuck, tight enough to keep it from flying out but light enough that it can be moved with a little pressure. With the lathe running fairly fast, a strip of about 1/8″ thick fiber-board or plastic, approximately 1/2″ to 3/4″ wide and 4″ and 6″ long is hand held at one end. The other end acts as a buffer, or spacer, between the end of the rotating work and any tool rigidly clamped in the toolholder. The operator manually advances the carriage and uses the tool to lightly push the board to contact the workpiece near its outer diameter. One or two light touches with the board will true up the work quite nicely. Once the work is trued and spinning smoothly against the board, the chuck can be tightened for machining.
Of course, as with any operation that involves holding something near the turning jaws of the lathe, use caution. Hold the board loosely and somewhat down on the face of the work so that any contact with the jaws will push the end of the board down and not back at the operator. Bring the carriage towards the work slowly, pay attention and don’t rush things. Used properly, this trick can really speed things up in the shop.