Axial Holding Power – Clamp-Type Shaft Collars

• Axial Holding Power of a Clamp-Type Shaft Collar is defined as the amount of axial load required to initiate slippage of a properly installed collar on a compatible shaft.
• It is dependent on the shaft and collar being wiped clean of all debris and excess oils prior to assembly.
• It is due to the force provided by the clamp screw(s), which depends on:
  • Screw size, threads-per-inch and resultant recommended seating torque.
  • Friction factor between screw and screw threads in collar
  • Screw and collar material

These results should be used as a guide only– Because there are so many variables involved in determining the actual axial holding power between a specific collar and shaft, it is not possible for Stafford to certify a single value for all situations. Instead, we can provide results that have been obtained from testing under a controlled set of conditions that represent a typical operating environment. They are to be used voluntarily and as an aid for estimating shaft collar performance. They should not, under any circumstances, be used as guaranteed values. The user must determine the product suitability in a particular application
 

AXIAL HOLD FOR ALLOY SCREWS IN STEEL COLLARS

AXIAL HOLD FOR STAINLESS SCREWS IN STAINLESS COLLARS

AXIAL HOLD FOR ALLOY METRIC SCREWS IN 1215 COLLARS

AXIAL HOLD FOR STAINLESS METRIC SCREWS IN STAINLESS COLLARS

USEFUL APPLICATION INFORMATION

• Aluminum Collars: 2024 aluminum is a strong alloy, but it is softer than the 1215 steel shown in the above examples. For both Alloy and Stainless screws in aluminum couplings, the screw torque should be 50% of that shown for alloy screws in 1215 collars and the resulting torsional hold will also be 50% of that shown for the 1215 collars.
• Shaft and Collar Prep: At a minimum, the shafts and coupling bores should be wiped clean of any foreign matter or excess oils. The clamping screws have an oil coating, which should remain.
• Installation: Wipe the shaft, then mount the collar and position as wanted. Tighten the screw to the recommended seating torque. For two piece collars, tighten the screws in small steps, (keeping the slot width the same on both sides), and sequentially, until the screws are at the recommended seating torque.
• Additional Axial and Torsional Hold
  • Keyways: Stafford offers many collars with keyways. These can allow for use over keyed shafts and can also provide additional torsional hold as well as positive radial orientation.
  • Larger Screws: Special collars (or our Heavy-Duty Clamp-Type Collars), with larger screws will offer added axial and torsional hold.
  • More Screws: Special collars with more screws will offer added axial and torsional hold.
• All examples are for static loads. We cannot provide data for loads with sudden impacts.
• Galling: Galling can be an issue with excessive tightening torque in stainless fasteners when installed in stainless collars. If this occurs, the screw and collar can weld together and both become unusable. The above results were obtained with screw torques that are reduced to minimize the possibility of galling. If appropriate to the application, the user may opt to apply a high pressure lubricant to the screws to allow for higher screw torque and thus higher collar axial and torsional hold.
• Very high axial loads can be exhibited by machining a groove in the shaft 0.001” wider than a two-piece collar sized to clamp on the diameter at the base of the groove.This then acts as a positive locator (like a shoulder), except with the added convenience that it is removable.