Ball Screw Interchange Guide: SFU, DFU, SFE and SFK Against Global Brands

October 2026 10 min read Selection Guide

Ball screws are the opposite of linear guides on standardisation. There is no industry-wide nut flange or thread-end convention to match the way guide footprints are copied, so a model-for-model substitution table for SFU, DFU, SFE or SFK simply cannot be honest. The rolled-screw codes themselves circulate widely, but the nut, the flange and the end machining behind the same code vary from maker to maker.

That is why this page is a method, not a chart. Two screws with the same shaft diameter and lead can still be different products once preload, accuracy grade and journal machining are fixed. The seven checks below are what our engineers actually verify when a customer sends an old part number.

Our range at a glance

The table below states, for every RFU Motion family, whether the designation itself is shared across the industry or is our own house code. That single distinction decides how the rest of the page applies to you.

What carries over between makers — and what does not

The 7-point check before you substitute

Seven checks, every time. Send us the old part number and, if you have it, the drawing — we will run this list and reply with the nearest standard RFU Motion screw or a machining proposal.

1. Shaft nominal diameter and lead — the starting point, but never the finish: two screws can share both and still not swap.
2. Nut flange type, bolt circle and flange thickness — round, square or kama flange; hole circle and thickness are the dimensions that stop a nut dropping in.
3. Shaft end machining — finished journals (bearings, coupling seats already turned) or blank ends machined by you; this decides the support units and coupling too.
4. Axial clearance and preload method — free, single-nut oversized-ball, or double-nut spacer preload; the behaviour of your axis depends on this more than on the brand.
5. Accuracy grade — C3 / C5 / C7 / C10 (or the equivalent JIS grade); rolled and ground screws live in different grades entirely.
6. Dynamic load rating Ca and static Coa — compare with your load and required life in revolutions, not just with the old number.
7. Critical speed, buckling and support arrangement — length, end fixity and rpm decide whether the substitute actually survives in your machine.

When you should not substitute

• Ground screw replaced by a rolled screw. Positioning accuracy is built into the thread, not into the mounting dimensions; a C7 rolled part will not do a C3 ground part’s job.
• Preloaded double nut for a clearance single nut (or the reverse) without re-checking drive torque, heat and life.
• Substituting the nut while keeping the old shaft, or vice versa: nut and shaft are ground as a set, and mixing them is not a repair, it is a new failure mode.
• High-speed spindles and vertical axes, where critical speed, lubrication and end-fixity requirements leave little room for substitution.

Why ball screws rarely have a model equivalent

A linear guide is standardised from the outside in: the footprint is the product, and the rolling elements are sealed inside. A ball screw is the reverse — the performance lives in the thread geometry, the preload and the end machining, which are exactly the parts each maker does differently. Two SFU-size screws from two makers can share a shaft diameter and a lead and still differ in flange bolt circle, journal steps and grade. Treat any ball screw substitution as a small engineering project, not a lookup.

Back to the cross reference overview

HIWIN, THK, PMI, TBI MOTION, ABBA, CPC, NSK, IKO, NB, SBC and Bosch Rexroth are trademarks of their respective owners. Brand names on this page identify dimension families only and do not imply endorsement, affiliation or authorised replacement status.