Shielded Set-Screw Shaft Collar: The Screw Head Sunk in a Groove, a Sprung Brass Band Snapped Over It (Rich, 1904)

"The collar is used in the ordinary way on the shaft, and when locked in place the spring-shield is snapped over it, as illustrated, and covers the projecting set-screw and furnishes a smooth outer surface, upon which it is impossible for the clothing of a workman to be caught."

Grip 55 mm round bar in the 3-jaw chuck. Face it, turn it to 52 mm for 30 mm, centre-drill, drill through 15 mm and ream 16 mm. With the parting tool, cut the groove A1 18 mm wide between two 4 mm flanges, down to a 30 mm hub A2. Turn a seat 2 mm wide and 0.6 mm deep on the inner rim of each flange, at the outside, for the shield. Chamfer the bore and part off 26 mm long; face the parted side.

Centre-punch the hub in the middle of the groove. In the machine vice on the drill press, drill through the hub into the bore with 6.8 mm and tap M8 with cutting oil. Opposite the hole, file a notch 3 mm wide through the seat and 4 mm deep in each flange, in line, for the shield's ends. Deburr the bore where the drill came through.

Cut a strip of 0.5 mm brass 22 mm wide and 169 mm long with the snips. Bend 4 mm at each end square to the strip with the pliers, the same way. Roll it by hand round the collar itself until the ends meet, the bent ends pointing in. File a small nick in one edge of the band beside the ends, for a screwdriver. Spring it open over the collar: it must snap into the seats with the ends down the notch and stay put.

Run an M8 x 10 hex screw into the hub until it just shows in the bore. Slide the collar along the shaft to its place, turn it so the screw is easy to reach, and tighten the screw onto the shaft with the spanner. Spring the shield over the groove with its ends into the notch. To move the collar, put a screwdriver in the nick, spring the shield off and slacken the screw.

**George H. Rich and Robert C. Rich** of Chicago, Illinois, US 774,199, dated 8 November 1904, filed 14 March 1904. They claimed a collar with a peripheral depression, a set screw whose head lies in it, and a cylindrical shield outside the screw in continuous contact with the collar; the flanges countersunk for it; and a single strip of spring sheet metal with its ends turned in and abutting, in notches in the flanges. Their hub has a boss A3 for the screw; a lathe cannot leave a boss in a turned groove, so our hub is thick all round. They say spring steel or brass; ours is brass. The patent gives no sizes; every size here is ours.