Few installation errors are as frustrating as fitting a one way clutch bearing the wrong way round. The machine runs, but it freewheels where it should lock, or locks where it should overrun, and the only fix is to strip the assembly and start again. A two-minute check of the locking direction before installation prevents hours of rework. This guide shows how to verify direction on a roller type one way clutch bearing such as the SUMA AA20.

Problem: The Direction Is Not Always Obvious

Unlike a plain bearing, a one way clutch has a defined driving direction and a defined overrunning direction. Some units have an arrow or a marked face; others do not, and identical-looking parts can be built to opposite hands. Assuming the direction instead of checking it is the most common cause of a clutch that will not lock.

Cause: Why Direction Is Easy to Get Wrong

• Handed parts. The same body size can be supplied in two opposite hands, so appearance alone does not reveal direction.
• Inner and outer race roles. On a roller freewheel, either the inner or the outer race may be the driving member, changing which way the unit must be fitted.
• No orientation mark. Unmarked units leave the installer to determine direction from the ramp geometry.

Solution: Test the Lock Before You Fit

Before installation, hold the non-driving race and turn the other race gently by hand. In the locking direction the clutch grips almost immediately; in the freewheel direction it turns smoothly with only the small drag torque of the design. On the AA20 roller freewheel the drag torque is 8.4 N cm, low enough to feel the difference clearly. Confirm that the race which must overrun matches the machine's motion, then mark the unit so it cannot be reversed during assembly. Because the AA type is non-bearing supported, ensure the supporting bearings, lubrication and sealing are also oriented correctly.

Application: Backstops and Overrunning Drives

Direction checks matter most on backstops, where a mistake lets a conveyor or bucket elevator run backwards, and on overrunning drives, where the wrong hand turns a driven roller into a brake. A simple bench test removes the risk, and it costs nothing more than a minute. Marking the correct hand on the one way clutch bearing before it leaves the bench keeps the next installer from repeating the mistake, and it turns a hidden hazard into a routine check.

Technical Checklist

• Identify the driving member and the overrunning member
• Confirm the locking hand against the machine's required motion
• Check drag torque to feel the freewheel direction
• Mark the unit for correct re-assembly orientation
• Verify the supporting bearing, lubrication and sealing arrangement

FAQ

How do I know which direction locks?

Turn each race gently by hand. The direction in which it grips is the locking direction; the direction in which it turns smoothly is the freewheel direction. Doing this before installation saves the cost of fitting and re-stripping a one way clutch bearing.

Why are there two hands of the same clutch?

The driving and overrunning members can be arranged in opposite ways to suit different machine layouts, so the same size can be supplied built to either hand.

Can I reverse a clutch that has been fitted backwards?

Not by rotating it. A one way clutch cannot be re-handed; it must be replaced with the correct hand for the application.

Get a Recommendation

Tell us the required locking direction, bore size and duty, and we will supply the correct hand from the AA20 one way clutch bearing range.