BK Fixed End Bearing Unit

What happens at the fixed end when feed reverses?

When a ball screw changes feed direction, the axial force acting through its supports also changes direction. Movement at the fixed end can contribute to lost motion even when the screw and nut are correctly matched. The BK Fixed End Bearing Unit provides axial location through a preloaded bearing arrangement while allowing the shaft to rotate.

This preload belongs to the support bearings. It does not preload the ball nut, correct screw lead error or establish a positioning accuracy for the entire axis. Keeping those functions separate helps identify which component needs attention when a machine develops reversal error.

The product photograph shows two different housings. The covered fixed-side unit and the exposed-bearing supported-side unit perform different jobs; they are not two views of an identical component. The loose locknut and retaining ring also belong to different parts of the shaft-retention arrangement.

The shaft-end drawing connects the bearing unit to the screw

A BK Fixed End Bearing Unit fits the machined journal, not the threaded working diameter of the ball screw. A request containing only the screw diameter therefore leaves an essential interface undefined. The journal diameter establishes the bearing fit; the shoulder and locking section establish where the shaft sits axially.

Journal length matters as well. The retaining components must secure the intended bearing stack rather than bottom against an unrelated step or thread limit. A replacement housing that looks correct externally can still be unsuitable if these shaft-end details differ.

The mounting interface completes the connection. Centre height places the screw axis relative to the nut housing, while the mounting-hole pattern determines how the support attaches to the bed. These dimensions should be checked together with the shaft profile, especially when retaining an existing screw.

The BK Fixed End Bearing Unit is therefore specified as part of the fixed-end assembly. The corresponding BF support, locknut and other accessories should be identified individually so that the photograph, drawing and supplied parts describe the same configuration.

FAQ

Q: Is BK the fixed side or supported side?
A: BK is the fixed side. BF is normally installed at the opposite supported end.

Q: Can BK and BF be exchanged?
A: No. Their bearing arrangements and installation functions are different.

Q: Does BK12 automatically fit every 12 mm ball screw?
A: No. The machined fixed-end dimensions must match the BK12 specification.

Q: Is a locknut part of the fixed-end arrangement?
A: Yes. The shaft's locking section and the corresponding securing components establish the fixed-end position.

Q: What should be provided when ordering the ball screw and BK unit together?
A: Send the screw model, complete fixed-end drawing, supported-end drawing and required BK/BF sizes.

About Us

Guangyuan supplies ball screws and their fixed- and supported-end units. Screw ends can be machined to confirmed drawings, allowing the journal, shoulder and threaded section to be prepared for the selected support. Drawing-based OEM/ODM enquiries are welcome. The minimum order quantity for BK supports is 20 pieces. Quotations should state whether the requirement is for BK units alone or includes matching BF supports and shaft-retention accessories.

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