BK/BF Support Unit Selection Guide

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.

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.

Fixed-side model such as BK12, FK15, or EK10.
Support-side model such as BF12, FF15, or EF10.
Coupling end diameter, length, and keyway requirement.
Installation space, overall length, and working travel.

Typical buyer situations

This topic usually appears in distributor stocking, repair replacement, machine retrofit, automation projects, and drawing-based purchasing. If a buyer sends only one model number, the supplier cannot judge the real use, packing risk, or whether machining upgrades are needed.

Details to confirm before quotation

To reduce repeated questions, the RFQ should cover product specification, use case, and delivery expectations together. The following points can be copied into the RFQ form or email.

Purchase purpose: distributor stock, repair replacement, machine project, or sample testing.
Specification: diameter, lead, overall length, thread length, nut type, and quantity.
Machining: cut-to-length, end machining, and whether BK/BF, FK/FF, EK/EF, or other supports must be matched.
Delivery: target quantity, expected lead time, packing, labels, shipping method, and whether shipment photos are required.

Common mistakes

A common mistake is asking only for unit price without application, quantity, or packing details. Another is sending photos without dimensions. This turns quotation into guesswork and can create errors in end machining, nut matching, or long-part shipping.

Next step

If the specification is clear, submit an RFQ directly. If the model or accuracy grade is still uncertain, describe the machine use and old part details so the supplier can recommend a standard part, bar stock, cut-to-length, or end machining route.