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Ready to install our FK, FKN, or FKNN ball-bearing sprag clutch units? This guide is designed to walk you through how to do just that.

Keep in mind: Our ball bearing sprag clutch comes with precision ball bearings, so external bearing support is not necessary.

Before Getting Started

Here are a few things to do before you start installation:

  • Clean the area you’ll use for installation – make sure there is no grease anywhere in the area.
  • Don’t apply pressure directly to the balls when installing.

If you have any questions or need assistance during installation, reach us via our contact us form or give us a call at 800.323.5725 and a technical support team member will assist you.

Press-Fit Installation

You can press-fit a ball-bearing sprag clutch on ferrous or nonferrous material. If you’re considering installing it on nonferrous material please contact us before you start.

The Mating Parts

You don’t need to harden and grind the ball bearing sprag clutch mating parts.

Make sure to thoroughly clean the mating parts to ensure they are grease-free.

Clamping Direction

You will see arrows on the inner ring of the ball-bearing sprag clutch that show the clamping direction of the inner ring.


The seals are not suitable to protect against constant high levels of liquid but do reliably protect against grease and dust.

Please note: The FK 6203-RS has one seal only, and it’s located on the freewheel side of the ball-bearing sprag clutch.

Achieve the Right Radial Clearance for Your Installed Ball Bearing Sprag Clutch

A radial clearance between C2 and C5 will be happen after installation.

If you want a clearance of C2, then your shaft needs to be manufactured at the highest allowed n6 tolerances. And your housing needs to be manufactured at the lowest allowed N7 tolerances.

Clutch Engagement Direction

Drawing of a clutch engagement direction

It’s not necessary to specify clutch engagement direction with our sealed (2RS) or open ball bearing sprag clutches.
or the ball-bearing clutches that are sealed on only one side (RS), you must specify the clutch engagement direction.

The single seal is always mounted beside the clutch, not beside the ball bearing.

Engagement direction “right:” Engagement direction of the inner ring, view at the seal Engagement direction “left:” When ordering a sprag Clutch with opposite engagement, the suffix “L” must be placed after the catalog number.

Ball Bearing Sprag Clutch Lubrication

Our open ball bearing sprag clutches are delivered with an oil preservative for rust protection and aren’t lubricated. Our sealed ball-bearing sprag clutches are delivered with grease lubrication that will last the lifespan of the clutch.

  • Outer ring with press-fit hub D = H6
  • Inner ring with press-fit shaft d = h5
  • Inner ring with keyway shaft d = js6 (k5)

Keyway specifications according to DIN 6885 with back clearance.

Misc. Information

Our ball-bearing sprag clutch units don’t need any retainers for axial or radial security.

For sprag clutch units with inner ring keyways (FN and FND series), make sure to secure them in the axial direction if the outer machine part (gear or lever) is not axially secured.

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