Screw Seating Torque – Clamp-Type Shaft Collars

2024 aluminum is a strong alloy but softer than 1215 steel. For both alloy and stainless screws in aluminum collars, apply 50% of the seating torque shown for alloy screws in steel collars. The resulting axial and torsional hold will also be approximately 50% of the steel collar values.

At a minimum, wipe the shaft and collar bore clean of any foreign matter or excess oils before assembly. Clamping screws are supplied with a protective oil coating; this coating should remain on the screw.

Mount the collar on the cleaned shaft and position it as required. Tighten the screw(s) to the recommended seating torque using a calibrated torque wrench or torque-limiting hex key. For two-piece collars, tighten screws incrementally and alternately—keeping the gap equal on both sides of the split—until both screws reach the recommended seating torque.

Mount the coupling loosely on the shafts and tighten the screws gently until resistance is felt. Then, further tighten in several steps, tightening all screws in each step, until all screws are at the recommended

Galling can occur when excessive torque is applied to stainless fasteners in stainless collars, potentially welding the screw and collar together. The torque values above are set conservatively to minimize this risk. If the application demands higher torque, applying a high-pressure anti-galling lubricant to the screw threads may allow higher seating torque and correspondingly greater holding performance.

All torque and holding values are based on static load conditions. Stafford cannot provide data for dynamic loads involving sudden impacts or shock loading.