National Spline-Drive Inverted Spotfacers combine Ruggedness, Positive Driving and Accurate Alignment with long life and easy assembly. Hardened and Ground Alloy Steel Pilots fit snugly in the cutters, while driving is accomplished through splines that are part of the pilot. These splines bear against slots in the cutter, giving an equalized drive with all the advantages of the ordinary spline shaft drive.
The cutter is retained by solid shoulders on the pilot, yet removal of the cutter is very easy. All that is necessary is to turn the cutter backwards on the pilot a small distance, then slide it off. Pilots have a spiral oil groove to facilitate proper lubrication.