After machining to the correct size, these internal expanding collets are used to hold different size piston blanks. At this point the internal piston skirt; the piston bosses; & the wrist pin hole have been completed. The wrist pin groove can be cut now or cut last, after finish machining of the piston crown & OD. Measure carefully to insure the correct dimension between the wrist pin grooves. The wrist pins should have no more than .005 end play. A very slightly tapered arbor is used for this process. The piston is wrung on to this arbor for machining of the groove. A special diamond coated tool cuts this .020 wide groove.
