Separate fixed side and support side first
BK, FK, and EK are usually fixed-side supports with bearing and locking structures for axial positioning. BF, FF, and EF are usually support-side units. The pair affects end machining dimensions.
| Comparison | BK (fixed side) | BF (support side) |
|---|---|---|
| Position | Drive end of the screw, holds axial position | Other end of the screw, supports only |
| Structure | Internal bearing plus locking | Plain support, no axial lock |
| Pairing | Used with BF | Used with BK |
| Effect on end machining | Needs journal, thread, and lock fit | Needs journal and bearing fit |
| When to choose | Drive end | Non-drive end |
Support model is not the same as screw model
Models such as BK12, BK15, and BK20 often relate to bearing bore and mounting dimensions, not directly to screw diameter. Confirm screw diameter, end journal, bearing length, and lock thread together.
Different brands may have different details
Even when the name is the same, dimensions can vary by brand. For end machining, use the real support unit, brand drawing, or customer-confirmed drawing as the reference.
The three things selection actually checks
| What to check | Where it comes from | What is lost without it |
|---|---|---|
| Bearing bore and mounting dimensions | Real unit, brand drawing | Ordering a unit that does not match |
| End machining dimensions | Support unit drawing plus screw end sizes | Screw will not enter the unit, or the bearing will not seat |
| Mounting direction and space | Machine layout, coupling model | Flange interference, coupling cannot be fitted |
Checking all three before releasing end machining is the order that saves the most rework. For the individual end items, see the BK/BF end machining guide.
RFQ checklist
- Fixed-side model such as BK12, FK15, or EK10.
- Support-side model such as BF12, FF15, or EF10.
- Screw diameter, lead, and thread length.
- End journal diameter, bearing length, and lock thread spec for both ends.
- Coupling end diameter, length, and keyway requirement.
- Installation space, overall length, and working travel.
FAQ
Do you supply BK and BF support units to traders? Yes. Traders ordering BK or BF support units receive the same confirmation as direct buyers: support model and brand, screw diameter, end journal, bearing length, lock thread, coupling end, and export packing. This avoids mismatches when the unit is resold with a matched ball screw.
Does BK12 mean the screw diameter is 12 mm? Not necessarily. BK12 usually relates to bearing bore and support unit mounting dimensions, not the full screw model. Confirm screw diameter, end machining, and coupling-end dimensions together.
Can the fixed side and support side be swapped? No. The fixed side carries bearings and a locking structure for axial location; the support side provides radial support only, so the two ends are machined differently.
Next step
Turn this guide into an RFQ
When the specification direction is clear, send the details below together with quantity, lead time, and packing requirements.
Include these details
- Support-unit model, end drawing, or old-part end photos.
- Bearing journal, shoulder, lock thread, keyway, and coupling-end dimensions.
- Overall length, thread length, quantity, inspection, and packing requirements.
Category
Related Technical Guides
Continue with similar buyer questions
BK/BF Ball Screw End Machining: Support Unit Drawing Guide
Confirm the BK/BF support model before machining the shaft ends, then verify the drawing, bearing seats, threads, coupling end, and assembly length.
Send end machining drawing
BF Ball Screw Support Unit Suppliers: Buying Guide
For a BF support-unit RFQ, state the model, shaft journal, lock thread, coupling end, and installation space.
Send support unit RFQ
Ball Screw End Machining Drawing Checklist
Before sending an end-machining drawing, check the fixed side, support side, datum, and tolerances.
Send end machining drawing