# Ball screw

A ball screw's shaft, or its flanged single ball nut, from TBI MOTION's SFU and SFNU series. The nut's flange follows DIN 69051 Form B: a round flange with two flats and six bolt holes.

- **Screw** (`part = "screw"`): the shaft, a plain cylinder at the screw's outside diameter d, `length` long, standing on the XY plane along +Z. The ball groove isn't drawn.
- **Nut** (`part = "nut"`): the flange, A across and B thick, with its face on the XY plane and its flats H apart, parallel to Y. Six X holes sit on the bolt circle W. The body, D across, rises from the flange to the nut's length L. The bore is the screw's outside diameter d.

| Model | d x lead | Ball Da | D | A | B | L | W | H | X | Nut weight | Shaft weight |
|---|---|---|---|---|---|---|---|---|---|---|---|
| SFU01204-4 | 12 x 4 | 2.5 | 24 | 40 | 10 | 40 | 32 | 30 | 4.5 | 0.13 kg | 0.87 kg/m |
| SFNU01605-4 | 16 x 5 | 3.175 | 28 | 48 | 10 | 45 | 38 | 40 | 5.5 | 0.183 kg | 1.56 kg/m |
| SFNU01610-3 | 16 x 10 | 3.175 | 28 | 48 | 10 | 57 | 38 | 40 | 5.5 | 0.215 kg | 1.56 kg/m |
| SFNU02005-4 | 20 x 5 | 3.175 | 36 | 58 | 10 | 51 | 47 | 44 | 6.6 | 0.306 kg | 2.45 kg/m |
| SFNU02505-4 | 25 x 5 | 3.175 | 40 | 62 | 10 | 51 | 51 | 48 | 6.6 | 0.336 kg | 3.83 kg/m |

## Source

TBI MOTION's ball screw catalogue, from a copy hosted by the distributor Anaheim Automation (document L011848, PDF of 2025-03-12): <https://anaheimautomation.com/media/anaheim/files/manuals/forms/L011848_-_Catalog.pdf>.

- "SFNU/SFU (DIN 69051 FORM B) Series Specifications", page C76 (rolled ball screws), with the same rows on page C48 (precision ground): d, lead I, ball Da, and the nut's D, A, B, L, W, H and X. The drawing for d ≤ 32 shows six X holes on the bolt circle W, 45° apart either side of the axis between the flats, at 45°, 90°, 135°, 225°, 270° and 315° measured from the flats' normal (the X axis here). It also places the flange at one end of the nut.
- "2-5 Ball Screw Weight List", page C85: the nut and shaft weights above.
- "2-1 Nominal Model Code of Ball Screw", page C35: S is a single nut, F a flange, and NU the NU-type nut.

**The names.** The old catalogue names these sfu1204, sfu1605, sfu1610, sfu2005 and sfu2505. The names carry no maker: in the market they mean a ball screw of that diameter and lead with a DIN 69051 Form B flanged nut. Each is mapped to TBI MOTION's model with that standard, diameter and lead. For 12 x 4 that is TBI's SFU01204-4. For the others it is TBI's SFNU type, a single flanged nut with TBI's NU-type nut inside, in the same DIN 69051 Form B table. TBI's SFU (U-type nut) rows don't have 16 x 5, 16 x 10, 20 x 5 or 25 x 5.

**Proportions, stated plainly.** The catalogue doesn't dimension the nut's inside, so the bore is the screw's outside diameter d, with no ball track drawn. The oil hole Q and the wiper aren't drawn. The shaft is a plain cylinder at d, which is what the old catalogue's "simple" shafts are.

**Mass.** The material is steel (`steel-generic`). The shafts come out at 0.888 kg/m (12) and 1.578 kg/m (16), against TBI's 0.87 and 1.56: within 2 %. The nuts are solid between the bore and the outside, without the ball track and return channels, so they come out heavier than TBI's weights: SFU01204-4 148 g against 130 g, and SFNU01605-4 218 g against 183 g.

## Catalogue models

The old catalogue's ball-screw entries have no models to measure. Each `<name> ball screw L<n> simple` entry maps to that model's shaft preset of that length. `<name> ball nut` and `<name> flange ball nut` both map to the model's nut, which has a flange. The `<name> nut housing` entries are left out: a nut housing isn't part of TBI MOTION's ball screw series, and the entries name no maker of one.