FOR 1 1/2 HP 4 SPLINE MACHINES (3EGEA) Spindles Fits 4 spline drive shafts. Spindle arbors have standard 5/8" 11 threaded shaft to accommodate 5/8" threaded insert cup type and 5/8" bushed hole edge type grinding wheels or 3/4" pilot thread to accommodate 3/4" bushed hole cup and edge type grinding .