How to Choose a One Way Bearing for High-Torque Applications: Torque Guide

For high-torque applications, choose a one way bearing with a rated TKN comfortably above the drive torque, remembering that peak torque is about 2 × TKN, and accept that high-torque models are larger and allow lower overrunning speed. Match bore, width and race hardness so the clutch carries the load without slipping. Torque margin, not price, protects the machine from shock and sudden reversal.

Why This Selection Goes Wrong

Mining, cement and crusher drives combine high torque with heavy shock loads. A clutch rated only at steady torque can slip at start-up or stall. Extra margin and a correctly hardened race keep the sprags locked under shock, which is why high-torque selection starts with the peak load rather than the running load.

How a Sprag One Way Clutch Works

A sprag clutch is a cage of small, precisely angled sprags running between an inner and an outer race. Turning one way, the sprags tilt and jam, locking the races together so torque is transmitted; turning the other way, they release and freewheel. SUMA DC series cages are GCr15 bearing steel at HRC 60–62 surface hardness (0.6 mm minimum) with HRC 35–45 cores, supplied without races so the customer's shaft and housing become the raceways.

Key Parameters and Why They Matter

Real SUMA Selection Data

Selection Advice: Overrunning, Indexing or Backstopping

The three duties are not interchangeable. Overrunning freewheels in one direction and locks in the other, so its overrunning speed limit governs the choice. Indexing produces accurate intermittent motion and is limited mainly by torque and indexing accuracy. Backstopping only holds against reverse rotation, so holding torque matters most and freewheel speed is low. Choosing the wrong duty is one of the most common causes of premature clutch failure.

How to Select, Step by Step

• Rate TKN above peak drive torque including shock.
• Check the lower overrunning speed of large models.
• Harden the shaft and housing to HRC 60–62.
• Confirm bore and width for the required load.
• Verify lubrication for the slow, heavy duty.

Typical Applications

• Mining equipment — heavy slow drives.
• Cement equipment — continuous high torque.
• Crushers — shock-resistant backstopping.

Installation and Maintenance Notes

• Harden the shaft and housing races to HRC 60–62 over at least 0.6 mm depth.
• Keep the race plain width free of recess within the sprag-space tolerance.
• Select lubrication and sealing to suit the operating temperature and speed.
• Confirm the locking direction matches the machine before installation.

FAQ

Q1: How much margin should I add?
A: Choose TKN above drive torque because peak is about 2 × TKN.

Q2: Do bigger clutches run faster?
A: No, high-torque models allow lower overrunning speed.

Q3: What material is used?
A: GCr15 bearing steel at HRC 60–62 surface hardness.

Q4: Can a small clutch be used with a shock load?
A: Only if its TKN exceeds the peak, or it will slip.