Shaft Collar - Set Screw Style

Set Screw Style

The first mass-produced shaft collars were set screw collars and were used primarily on line shafting in early manufacturing mills. These early shaft collars were solid ring types, employing square-head set screws that protruded from the collar. Protruding screws proved to be a problem because they could catch on a worker's clothing while rotating on a shaft, and pull them into the machinery.

Shaft collars saw few improvements until 1910 through 1911, when William G. Allen and Howard T. Hallowell, Sr, working independently, introduced commercially viable hex socket head set screws, and Hallowell patented a shaft collar with this safety-style set screw. His safety set collar was soon copied by others and became an industry standard. The invention of the safety set collar was the beginning of the recessed-socket screw industry.

Set screw collars are best used when the material of the shaft is softer than the set screw. Unfortunately, the set screw causes damage to the shaft – a flare-up of shaft material – which makes the collar harder to adjust or remove. It is common to machine small flats onto the shaft at the set screw locations to eliminate this problem.