Shaft Collar Types, Performances, and Design Considerations

Release Date : March 18, 2011

Shaft collars are versatile components that have evolved from the basic set-screw collar to the high performing one- and two piece clamp collars. This video explains the differences between shaft collars and wraps up with an axial load comparison test.


Set Screw Shaft Collar: The set screw shaft collars derives its holding power from a single screw as it is tightened onto the shaft. To reach maximum holding power, the shaft must be a softer material than that of the screw. The very nature of the set screw collar is its greatest fault. And as a result, the tightening of the screw causes a deformation of the material around the point resulting in a raised burr on the surface of the shaft. The damage to the shaft makes it difficult to replace or re-position the collar. Removal may require the use of specialized equipment. Due to the shaft damage, I won’t be able to reinstall or re-position the collar without the replacement of the shaft. Here are some examples of shaft damage caused by set screw collars. This type of damage is caused by multiple adjustments of the collar. And this form of damage is caused by axial movement of the collar.

One-Piece Collar: One-piece clamp style shaft collar is an improvement of the set screw collar as they do not destroy the shaft. Unlike the set screw collar, the one-piece collar can be used on a split hub application such as this one. One-piece shaft collars utilize forged socket head cap screw and the use of vac saw cut to achieve maximum clamping force. As you can see removing a clamp style collar is a lot easier than moving a set screw collar. The shaft is undamaged, and the collar can easily be repositioned.

Two-piece Shaft Collar: two-piece shaft collars can be used when its difficult to install a one-piece shaft collar. They offer the same benefits as the one-piece collar with additional versatility and convenience. I can easily install a two-piece collar as a stop on a pillow block without removing any other components. This results in reduced labor costs and down time when adjustment, removal or replacement is necessary. Tightening the screws clamp the collar onto the shaft for uniform distribution of forces around the shaft circumference. To achieve the maximum holding power, the forged socket head cap screws must be tightened in an alternating pattern to maintain an even saw cut gap.

Shaft Collar Axial Load Test: The universal testing machine is a device used to test the tensile and compressive stress of materials, components and assemblies. For this demonstration, we are using the machine to apply compressive force to the shaft collar assembly to simulate an axial load. The force at which the collar begins to slip on the shaft is shown in the dial in pounds. As you can see, single and two-piece shaft collars offer greater axial holding capabilities as compared to the traditional set screw type collar.

Helpful Resources for Curved Jaw Couplings

Getting a Hold on Shaft Collars: Choosing the Correct Shaft Collar for the Job - This product spotlight gives the pros and cons when choosing a shaft collar.

Choose a Shaft Collar - This page will shows you all the variety of Shaft Collars that Ruland offers.

Coupling Comparison Guide -This is a chart that shows the comparison of Ruland servo coupling on critical performance characteristic.

Clamp Style Shaft Collars for Medical Equipment - Ruland clamp style shaft collars are manufactured from select materials with fine finishes, high holding power, and a precise face to bore relationship making them ideal for the demands of medical equipment.

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