BK Ball Screw Support Unit – Fixed Side Square Type

The BK Ball Screw Support Unit is a square-type fixed-side bearing support used to locate and support the fixed end of a ball screw shaft. In a typical ball screw installation, the BK unit is installed at the fixed end, while a BF support unit is normally used at the opposite supported end.

DLY supplies BK10, BK12, BK15, BK17, BK20, BK25, BK30, BK35 and BK40 models, covering fixed-end shaft diameters from 10 mm to 40 mm. The appropriate BK model should be selected according to the machined shaft-end dimensions rather than only the nominal diameter of the ball screw.

For customers purchasing a complete ball screw assembly, DLY can also help confirm the matching ball screw, fixed-side support, supported-side support and shaft-end machining requirements before production.

BK Ball Screw Support Unit Models

The BK series includes nine commonly used sizes from BK10 to BK40. The number in the BK model corresponds to the fixed-end shaft diameter d1 used for support-unit matching.

All dimensions are in millimeters. The dimensional data above is intended for model identification and preliminary selection. Please confirm the complete dimensions or drawing before ordering.

What Is a BK Fixed-Side Support Unit?

A ball screw normally requires support at both ends of the screw shaft, but the two ends do not perform exactly the same function. The BK support unit is installed on the fixed side, where the screw shaft needs stable axial positioning during rotation.

The opposite end normally uses a BF supported-side unit. This BK/BF arrangement allows the fixed end to establish the axial position of the screw while the other end provides additional shaft support.

For this reason, BK and BF should not simply be selected as two interchangeable bearing blocks. The shaft-end machining and installation position must correspond to the fixed-side and supported-side structure.

How to Select the Correct BK Model

The first dimension to check is the machined fixed-end diameter d1. For example, BK12 corresponds to a 12 mm fixed-end shaft diameter, while BK20 corresponds to a 20 mm fixed-end shaft diameter.

However, selecting a support unit only from the model number is not sufficient for a custom ball screw. The shaft shoulder, threaded section, bearing seat, mounting dimensions and available machine space should also be checked before machining.

If the ball screw has not yet been machined, send DLY the screw diameter, lead, total length and required support arrangement. If an existing shaft has already been machined, a shaft-end drawing with dimensions is the most reliable way to confirm the correct BK support unit.

BK Series Dimensional Notes

DLY BK support units cover fixed-end shaft diameters from 10 mm to 40 mm. As the model size increases, the housing width, height, shaft center height and mounting-hole spacing also increase.

For the supplied dimensional specification, the mounting-related dimensions b and shaft center height h are specified with a tolerance of ±0.02 mm. The mounting holes use four through holes with corresponding counter-bore dimensions according to the individual BK model.

Because the installation dimensions differ between models, machine-base hole positions should be checked against the selected support-unit drawing before machining the mounting surface.

BK and BF: Which Side Should Each Support Be Installed?

BK and BF are commonly used as a matched support arrangement, but their installation positions are different.

If you need both ends of the support system, you can also view DLY's complete Ball Screw Support range.

Ball Screw End Machining and Support Matching

The support unit and ball screw shaft end must match each other. A BK20 support does not mean that every 20 mm nominal-diameter ball screw can be installed directly into a BK20 unit. The relevant dimension is the machined fixed-end bearing seat.

For custom assemblies, DLY can confirm the ball screw and support arrangement before end machining. This is especially useful when customers purchase the ball screw, BK/BF supports, coupling and related installation components together.

When requesting a quotation, providing an existing drawing or sample dimensions can reduce the risk of selecting the wrong support model.

Typical Applications

BK ball screw support units are commonly used in ball screw drive systems where a square fixed-side mounting structure is required. Typical applications include CNC machine axes, automation equipment, linear modules, positioning mechanisms, packaging machinery, woodworking machinery and other industrial linear-motion systems.

The final BK model should be selected according to the ball screw shaft-end design and actual installation dimensions rather than the machine type alone.

Ordering BK Ball Screw Support Units from DLY

DLY supplies BK10–BK40 fixed-side support units for individual replacement, machine assembly and batch purchasing. MOQ starts from 1 piece, and matching or customization can be discussed according to the ball screw and installation requirements.

For faster model confirmation, please send:

• Required BK model, such as BK12, BK20 or BK30
• Ball screw model and diameter
• Fixed-end shaft drawing or dimensions
• Required quantity
• Whether BF supported-side units are also required