4 Jaw Chuck



The Four Jaw chuck is a precise tool that can be used in-conjunction with an indicator to accurately center a piece of stock to within a thousandth of an inch. Each of the four jaws is moved independently of the rest. On the face of the chuck are concentric circles which help with the rough alignment of the stock when first putting it in the jaws. The indicator is then placed in the tool post holder, and put in place so that it rides up against the stock and is free to move both in and out without disturbance. As the stock is rotated the indictor shows the variation of concentricity. Stock is centered by lightly tightening and loosing apposing sides of the chuck until the indicator reads variation to within a couple thousandths of an inch. Near the end of centering, it is best to only tighten, to ensure that when you reach center the stock is securely held. Tightening at the end may be only gently tapping the chuck wrench, which can move the stock by several thousandths, with practice this will become a quick procedure.