Just slip the ring core onto the step that fits best, make sure it's properly seated, then lightly tighten with the allen key. The smallest size ring may require a small squeeze on the mandrel to allow the ring to pop on.
This will cause the mandrel to expand slightly to produce a solid grip on the ring core.
Made from mild steel
Includes a 1/2" diameter shank for use in a collet, 4 jaw chuck or drill chuck
Mandrel Fits USA ring sizes 4-8.5, whole and half sizes
