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Brand: HIWIN
HIWIN BK/BF Ball Screw Support Units, Fixed and Supported End
Description
The HIWIN BK and BF support units are the square-housing pair used to mount a ball screw: the BK is the fixed end that takes the axial thrust with a pair of angular contact bearings, and the BF is the supported end that carries radial load with a deep groove bearing. Both arrive greased and adjusted, so no extra alignment is needed at assembly.
Fixed and supported ends for ball screw axes
HIWIN support units combine a bearing housing, bearing, holding lid, seal, lock nut and set screws. The compact size helps in narrow spaces and the greased, pre-adjusted bearings cut installation time. The catalog lists 11 types and recommends the WBK series where a higher axial thrust and stiffness are needed.
Match the precision class to the screw: C3 supports with a C3 screw, C5 screws with C3 or C5 supports, and C7 screws only with C7 supports.
Technical specifications
| Parameter | Specification |
|---|---|
| Fixed end (BK) | Angular contact bearing pair, 30 degree standard; 40 degree for 35 and 40 mm |
| Supported end (BF) | Deep groove ball bearing of series 6 with ZZ shields |
| Bore sizes | 10 to 40 mm (BK10 to BK40; BF10 to BF40) |
| Precision classes | C3, C5 and C7 (C3 and C5 use P5 bearings, C7 uses P0) |
| Bearing assembly | DF type with preload between the two bearings |
| Surface treatment | Blackening standard; N for nickel plating, made to order |
| Grease | Pre-packed with #2 Li/Ca soap grease |
| Family types | Fixed AK, BK, EK, FK, LK; supported AF, BF, EF, FF, LF, LFA; heavy load WBK |
| Code example | BK 30 B C3 N: size 30, 40 degree bearing, C3, nickel |
BK fixed-end sizes and ratings
Axial load limit and basic dynamic load rating Ca, per the catalog purchasing guide. The 25 and 30 mm sizes also come as BK25B and BK30B with 40 degree bearings.
| Model | Bore mm | Bearing | Axial limit kN | Ca kN |
|---|---|---|---|---|
| BK10 | 10 | 7000A | 1.9 | 6.4 |
| BK12 | 12 | 7001A | 2.1 | 6.9 |
| BK15 | 15 | 7002A | 2.4 | 7.3 |
| BK17 | 17 | 7203A | 4.1 | 12.9 |
| BK20 | 20 | 7004A | 4.2 | 12.9 |
| BK25 | 25 | 7205A | 7 | 19.3 |
| BK30 | 30 | 7206A | 9.8 | 26.8 |
| BK35 | 35 | 7207B | 14.4 | 37.3 |
| BK40 | 40 | 7208B | 18 | 44 |
BF supported-end sizes and ratings
The BF mounts opposite the fixed end; its bore can be equal to or smaller than the nominal size of the screw, so BF10 holds an 8 mm journal.
| Model | Journal mm | Bearing | C kN | C0 kN |
|---|---|---|---|---|
| BF10 | 8 | 608ZZ | 3.3 | 1.3 |
| BF12 | 10 | 6000ZZ | 4.5 | 1.9 |
| BF15 | 15 | 6002ZZ | 5.6 | 2.8 |
| BF17 | 17 | 6203ZZ | 9.5 | 4.8 |
| BF20 | 20 | 6004ZZ | 9.4 | 5 |
| BF25 | 25 | 6205ZZ | 14 | 7.8 |
| BF30 | 30 | 6206ZZ | 19.5 | 11.3 |
| BF35 | 35 | 6207ZZ | 25.7 | 15.3 |
| BF40 | 40 | 6208ZZ | 29.1 | 17.9 |
Ordering and selection
Handle the fixed-end unit as a sealed assembly. The catalog notes that the housing, seal, angular contact bearing and holding lid are installed and adjusted at the factory, and that taking them apart may affect the precision. Only the lock nut and set screws are meant to be tightened at assembly.
The code lists product type, nominal size, bearing type, precision level and surface treatment. Before ordering, confirm the screw end machining, the bore, the precision class and the bearing type, and use BK with BF only when the screw journal suits both. Use the catalog dimension tables for the housing, hole pattern and lock nut.
Seven Star LLC is an independent supplier in Muscat; send the code, the screw drawing and the quantity with your RFQ. The linked PDF is the full HIWIN support unit catalog, unchanged. More items are in our product range.
Related HIWIN products: HIWIN Super S FSC Precision Ground Ball Screw with Flange Nut, HIWIN Super Z FSZ Miniature Ground Ball Screw with Flange Nut, HIWIN SP-FS Flange Type Linear Ball Spline Nut and Shaft, HIWIN EGH-CA Low Profile Linear Guideway Block and Rail, HIWIN MGN-C Miniature Linear Guideway Block and Rail and HIWIN WEH-CA Wide Rail Linear Guideway Block and Rail.
Datasheets & Documents
- Catalog HIWIN Support Unit Technical Information catalog B03TE03-1907 (34 pages) Download
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About brand
HIWIN Technologies is a Taiwanese manufacturer of motion control and linear transmission components, founded on 11 October 1989 and headquartered in Taichung. It started as a maker of ball screws and linear motion parts, has been listed on the Taiwan Stock Exchange since 2010, and is one of the world's largest ball screw producers.
Seven Star LLC sources and supplies these components for machine builders, fabrication shops and maintenance teams in Oman.
HIWIN company profile
| Founded | 11 October 1989, Taichung, Taiwan |
|---|---|
| Headquarters | Taichung, Taiwan |
| Listing | Taiwan Stock Exchange since 2010 |
| Product families | Ballscrews, linear guideways, linear and torque motors, rotary tables, AC servo motors and drives, single-axis robots and positioning stages, articulated and SCARA robots |
Milestones
- 1989: HIWIN is founded in Taichung.
- 2010: HIWIN Technologies lists on the Taiwan Stock Exchange.
HIWIN products listed here
This page groups the ball and roller linear guideway series such as HG, EG, WE, MG, CG and RG, the quiet QH and QE series with SynchMotion technology, crossed roller bearings, ball splines and ball screws. The catalog chapter for each series is linked on its product page.
Where linear guideways and ball screws are used
Typical uses are machine tools, packaging and assembly automation, gantry and pick-and-place axes, measuring equipment and semiconductor handling. Ball screws convert rotation to linear motion, guideways carry and guide the moving mass, and crossed roller bearings carry combined loads in rotary tables and robot joints.
What to send with an enquiry
Send the series and size, block or nut type, accuracy class, preload class, rail or shaft length and the quantity. For a replacement, copy the full model number from the label of the part in service.
HIWIN products we list
Facts checked against HIWIN company profiles and Taiwanese press, October 2026.
Related products
Frequently Asked Questions
What is the difference between BK and BF?
BK is the fixed-end unit with angular contact bearings that take axial load. BF is the supported-end unit with a deep groove bearing that carries radial load only.
Which precision class should I pick?
Use C3 with a C3 screw, C3 or C5 with a C5 screw, and C7 only with C7 screws, as the catalog advises.
When is a 40 degree bearing used?
The standard is a 30 degree bearing. Above 20 mm a 40 degree bearing is available, and 35 and 40 mm are only offered with 40 degree.
What surface finish do the units have?
Blackening is standard. Nickel plating, marked N, is made to order.
Is Seven Star LLC a distributor of HIWIN?
No. Seven Star LLC is an independent supplier in Muscat that sources HIWIN products through commercial channels and checks the model against the manufacturer catalog before quoting.
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