Chuck setting rings are circular cut grooves in the face of the 4 jaw chuck; their purpose is to enable the turner to correctly set the position of the jaws to suit the job to be gripped in the chuck.
Procedure:
1. Measure the size of the work to be gripped in the chuck (regular or irregular shape). Regular shaped work, e.g. round, measure its diameter, set the two opposite jaws with either point A or B on the circle nearest the diameter of work to be gripped.
2. Measure the difference (engineer's rule) between the jaw settings and work diameter, adjust one jaw +/- half the difference.
3. Adjust opposite jaw to read work diameter.
4. Make a mental note of the jaw positions which should be equi-distant from the setting ring.
5. Set the other two jaws to their correct postions. Slacken off two adjacent jaws to enable to work to be mounted in the chuck, then finally tightened up to secure the workpiece in position.