Glen2 --The following short essay about quickly centering work with a 4-jaw chuck was originally posted on Usenet by a gentleman (now deceased) named Robert Bastow: Quick tip for setting work true in a 4 jaw in two revolutions! (I learned this, setting up roll turning lathes with 108" swing and a jogging speed of two to four MINUTES per revolution.) 1. Revolve the work through one revolution..noting the TOTAL swing of the indicator needle. Bring the spindle to a halt at the MIDPOINT of the swing and ZERO the dial to the needle. 2. Revolve spindle to bring jaw one to be "on the plunger". Adjust jaw one and jaw three to ZERO the needle again. 3 Rotate 1/4 turn and adjust jaws two and four to re-zero needle. Job is done! Robert Bastow
I'll only add a couple of things:
1. Set your indicator as near the chuck jaws as clearance allows. (A rubber hammer applied judiciously to the free end of a loosely-chucked shaft is the ticket to centering the tailstock end of the shaft.) 2. Using two chuck keys, one in each of two diametrically-opposite adjustment worms, operated simultaneously by turning both in the same direction the same amount so that one jaw moves toward center while the other moves away from center, will make it easier to coordinate your movements while struggling to master the 4-jaw. A skilled operator can center a normal-size workpiece in a 4-jaw in a minute or two, and that particular skill can be developed with just a bit of practice. John
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