(1) All revolving collars, including split collars, must be cylindrical.

(2) Screws or bolts used in collars must not project beyond the largest periphery of the collar.

(3) Shaft couplings must be constructed to prevent hazard from bolts, nuts, set screws, or revolving surfaces. Bolts, nuts, and set screws are permitted where they are covered with safety sleeves or where they are used parallel with the shafting and are countersunk or where they do not extend beyond the flange of the coupling.