Rockler - Rockler- Center Finder/Caliper Gauge
Small steps, graduated in 1/8-in. increments, make setting calipers a breeze.
Rockler’s Center Finder/Caliper Gauge makes quick work of setting dial calipers and finding the centers of spindles. I commonly adjust my calipers by sight using a ruler or vernier caliper, which can be imprecise, especially if you’ve rounded the tips of the calipers to prevent them from marring or catching the workpiece. But the caliper gauge turns the process of setting the calipers into a function of feel rather than one of sight. Because the caliper tips seat squarely at each measurement increment (from 1/8 in. to 5 in.), the gauge can be real handy for beginning turners.
The center finder is a breeze to use, too, and it works for square or round spindle stock.