To meet those demands, engineers at Royal Products, Hauppage, N.Y. (, designed their Precision ER line of collet chucks out of 5-60 Rockwell-C alloy steel for strength and rigidity. Runout is guaranteed to be less than 0.0001 in. between the OSD taper and collet socket. This accuracy helps evenly distribute chip loads, which increases cutting tool life. The tapered shank is ground to ANSI AT-3 specs for a precise fit with the machine-tool spindle taper, and a specially ground clamping nut ensures near-perfect roundness. These features reduce vibrations, and increase rigidity and clamping forces. The chuck is also balanced to G2.5 at 18,000 rpm for high-speed use.