SFA Ball Screw Nut
DLY SFA series ball screw nuts are single-flange A-type nuts using an end-cap ball circulation system. This configuration is designed for ball screw assemblies where high feed speed, smooth ball return and a stable flange mounting interface are required.
The series includes standard-lead and large-lead models in multiple screw sizes. SFA dimensions follow the DIN 69051 Form B flange format, while the mounting-hole arrangement changes between smaller and larger nominal screw sizes.
SFA nuts can be supplied separately for confirmed replacement requirements or together with a matching ball screw shaft. For custom assemblies, screw length and shaft-end machining can be produced according to the customer's drawing or machine installation dimensions.
SFA End-Cap Circulation Design
The SFA series uses an end-cap circulation structure. During operation, the steel balls roll between the screw raceway and the nut raceway to transmit axial load. At the end of the loaded path, the balls are guided through the return structure and circulated back into the working raceway.
This circulation method is suitable for high-speed positioning and is also used in SFA models with relatively large leads. Compared with internal-circulation nut structures, the SFA configuration uses a different ball-return arrangement and therefore has its own nut body, flange and dimensional characteristics.
The circulation type should be considered together with screw diameter, lead, required feed speed, axial load, nut dimensions and available installation space when selecting a new assembly or replacement nut.
High-Speed A-Type Nut with Dust Protection
The SFA configuration belongs to the A-type ball nut family, intended for applications requiring high-speed motion and improved protection around the screw raceway. Dust-protection components at the ends of the nut provide a wiping effect around the screw surface and help limit the entry of external particles into the circulation area.
These components are part of the nut protection system, but they do not replace external machine protection. In environments with heavy chips, cutting fluid, wood dust or other contaminants, suitable covers or bellows should still be used together with correct lubrication and regular maintenance.
SFA DIN 69051 Form B Dimensions
SFA nuts use a flange mounting interface, but the flange-hole arrangement is not identical across the complete series. Models with nominal screw diameters up to 32 mm and models from 40 mm upward use different mounting-hole layouts. The drawing below should therefore be checked together with the dimensional table when confirming installation or replacement.
SFA DIN 69051 Form B Series Specifications
The table lists the main dimensional and load data for the DLY SFA series. Dimensions are in millimeters unless otherwise stated. Models with the same basic screw size can have different circulation specifications, nut lengths, load ratings and rigidity values, so the complete model should be confirmed before ordering.
| Model | Shaft Diameter d | Lead | Ball Diameter Da | D | A | E | B | L | W | H | X | Q | n | Ca | C0a | Rigidity kgf/μm |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| SFA1205-2.8 | 12 | 5 | 2.5 | 24 | 40 | 5 | 10 | 30 | 32 | 30 | 4.5 | - | 2.8x1 | 661 | 1316 | 19 |
| SFA1210-2.8 | 12 | 10 | 2.5 | 24 | 40 | 5 | 10 | 42 | 32 | 30 | 4.5 | - | 2.8x1 | 642 | 1287 | 19 |
| SFA1605-3.8 | 15 | 5 | 2.778 | 28 | 48 | 5 | 10 | 31 | 38 | 40 | 5.5 | M6 | 3.8x1 | 1112 | 2507 | 30 |
| SFA1610-2.8 | 15 | 10 | 2.778 | 28 | 48 | 5 | 10 | 42 | 38 | 40 | 5.5 | M6 | 2.8x1 | 839 | 1821 | 23 |
| SFA1616-1.8 | 15 | 16 | 2.778 | 28 | 48 | 5 | 10 | 43 | 38 | 40 | 5.5 | M6 | 1.8x1 | 552 | 1137 | 14 |
| SFA1616-2.8 | 15 | 16 | 2.778 | 28 | 48 | 5 | 10 | 59 | 38 | 40 | 5.5 | M6 | 2.8x1 | 808 | 1769 | 22 |
| SFA1620-1.8 | 15 | 20 | 2.778 | 28 | 48 | 5 | 10 | 50 | 38 | 40 | 5.5 | M6 | 1.8x1 | 554 | 1170 | 14 |
| SFA2005-3.8 | 20 | 5 | 3.175 | 36 | 58 | 7 | 10 | 33 | 47 | 44 | 6.6 | M6 | 3.8x1 | 1484 | 3681 | 37 |
| SFA2010-3.8 | 20 | 10 | 3.175 | 36 | 58 | 7 | 10 | 52 | 47 | 44 | 6.6 | M6 | 3.8x1 | 1516 | 3833 | 40 |
| SFA2020-1.8 | 20 | 20 | 3.175 | 36 | 58 | 7 | 10 | 52 | 47 | 44 | 6.6 | M6 | 1.8x1 | 764 | 1758 | 19 |
| SFA2020-2.8 | 20 | 20 | 3.175 | 36 | 58 | 7 | 10 | 72 | 47 | 44 | 6.6 | M6 | 2.8x1 | 1118 | 2734 | 29 |
| SFA2505-3.8 | 25 | 5 | 3.175 | 40 | 62 | 7 | 10 | 33 | 51 | 48 | 6.6 | M6 | 3.8x1 | 1650 | 4658 | 43 |
| SFA2510-3.8 | 25 | 10 | 3.175 | 40 | 62 | 7 | 12 | 52 | 51 | 48 | 6.6 | M6 | 3.8x1 | 1638 | 4633 | 45 |
| SFA2525-1.8 | 25 | 25 | 3.175 | 40 | 62 | 7 | 12 | 60 | 51 | 48 | 6.6 | M6 | 1.8x1 | 843 | 2199 | 22 |
| SFA2525-2.8 | 25 | 25 | 3.175 | 40 | 62 | 7 | 12 | 85 | 51 | 48 | 6.6 | M6 | 2.8x1 | 1232 | 3421 | 34 |
| SFA3205-3.8 | 32 | 5 | 3.175 | 50 | 80 | 9 | 12 | 35 | 65 | 62 | 9 | M6 | 3.8x1 | 1839 | 6026 | 51 |
| SFA3210-3.8 | 31 | 10 | 3.969 | 50 | 80 | 9 | 12 | 53 | 65 | 62 | 9 | M6 | 3.8x1 | 2460 | 7255 | 55 |
| SFA3220-2.8 | 31 | 20 | 3.969 | 50 | 80 | 9 | 12 | 72 | 65 | 62 | 9 | M6 | 2.8x1 | 1907 | 5482 | 43 |
| SFA3232-1.8 | 31 | 32 | 3.969 | 50 | 80 | 9 | 12 | 78 | 65 | 62 | 9 | M6 | 1.8x1 | 1257 | 3426 | 27 |
| SFA3232-2.8 | 31 | 32 | 3.969 | 50 | 80 | 9 | 12 | 110 | 65 | 62 | 9 | M6 | 2.8x1 | 1838 | 5329 | 42 |
| SFA4005-3.8 | 40 | 5 | 3.175 | 63 | 93 | 9 | 14 | 39 | 78 | 70 | 9 | M8 | 3.8x1 | 2018 | 7589 | 60 |
| SFA4010-3.8 | 38 | 10 | 6.35 | 63 | 93 | 9 | 14 | 57 | 78 | 70 | 9 | M8 | 3.8x1 | 5035 | 13943 | 67 |
| SFA4020-2.8 | 38 | 20 | 6.35 | 63 | 93 | 9 | 14 | 78 | 78 | 70 | 9 | M8 | 2.8x1 | 3959 | 10715 | 54 |
| SFA4040-1.8 | 38 | 40 | 6.35 | 63 | 93 | 9 | 14 | 96 | 78 | 70 | 9 | M8 | 1.8x1 | 2585 | 6648 | 34 |
| SFA4040-2.8 | 38 | 40 | 6.35 | 63 | 93 | 9 | 14 | 136 | 78 | 70 | 9 | M8 | 2.8x1 | 3780 | 10341 | 52 |
| SFA5005-3.8 | 50 | 5 | 3.175 | 75 | 110 | 10.5 | 15 | 42 | 93 | 85 | 11 | M8 | 3.8x1 | 2207 | 9542 | 68 |
| SFA5010-3.8 | 48 | 10 | 6.35 | 75 | 110 | 10.5 | 18 | 57 | 93 | 85 | 11 | M8 | 3.8x1 | 5638 | 17852 | 79 |
| SFA5020-3.8 | 48 | 20 | 6.35 | 75 | 110 | 10.5 | 18 | 98 | 93 | 85 | 11 | M8 | 3.8x1 | 5749 | 18485 | 87 |
| SFA5050-1.8 | 48 | 50 | 6.35 | 75 | 110 | 10.5 | 18 | 117 | 93 | 85 | 11 | M8 | 1.8x1 | 2946 | 8749 | 42 |
| SFA5050-2.8 | 48 | 50 | 6.35 | 75 | 110 | 10.5 | 18 | 167 | 93 | 85 | 11 | M8 | 2.8x1 | 4308 | 13610 | 65 |
Model availability and special specifications should be confirmed before ordering. For replacement projects, dimensions can be checked according to the existing drawing, sample or measured installation data.
How to Read an SFA Model
The complete SFA designation contains more information than the basic screw diameter and lead. For example, in a model such as SFA1605-3.8, SFA identifies the nut series, 1605 identifies the nominal screw size and lead group, and the suffix identifies the circulation turn-and-row specification used for that nut configuration.
Different circulation specifications within the same nominal size can have different nut lengths, dynamic load ratings, static load ratings and rigidity values. For replacement projects, the complete model and dimensional data should therefore be checked instead of selecting only by a simplified designation such as 1605 or 2020.
How to Select an SFA Ball Screw Nut
Start with the required screw diameter and lead, then check the complete nut dimensions, flange mounting-hole layout, circulation specification, load rating and rigidity against the machine design. For high-speed axes, screw length, rotational speed and support arrangement must also be evaluated together.
Large-lead SFA models provide more linear travel per screw revolution, but a larger lead should not be selected only for speed. Axial load, required acceleration, rigidity, critical speed, positioning requirement and the complete support structure should be considered before confirming the assembly.
Replacing an Existing SFA Nut
For replacement projects, the nominal diameter and lead alone are not enough to guarantee interchangeability. Nuts with similar basic size markings can still differ in nut length, flange dimensions, mounting-hole positions, circulation specification and the matching screw raceway.
If the complete original model is available, send the model marking together with clear photos of the nut and screw shaft. If the model cannot be identified, measure the nut overall length, flange dimensions, mounting-hole layout, screw diameter and lead and provide a drawing whenever possible.
Where compatibility is uncertain, confirming the drawing, measured dimensions or physical sample before production is safer than assuming that two nuts with the same nominal size can be installed directly on the same screw shaft.
SFA, SFU and SFY Nut Configurations
SFA, SFU and SFY are different ball nut configurations rather than interchangeable names for the same product. The circulation system, nut body and mounting dimensions should be matched to the machine design.
| Series | Nut Configuration | Selection Focus |
|---|---|---|
| SFA | A-type flange with end-cap circulation | High-speed positioning, large-lead options and SFA flange dimensions |
| SFU | Standard flange nut with internal circulation | Standard compact ball screw assemblies and common machine-axis layouts |
| SFY | Y-type nut with end-cap circulation | High-speed applications using the corresponding Y-type mounting dimensions |
SFA Nut and Matching Ball Screw Supply
DLY can supply an SFA nut separately when the required model and matching screw specification have been confirmed. For new machine builds or complete replacement projects, the nut can also be supplied together with a matching ball screw shaft.
Screw length and shaft-end machining can be produced according to the customer's drawing. Support units, nut housings and couplings can also be confirmed together when the customer requires a complete mechanical transmission package.
What to Send for Model Confirmation
New ball screw assembly: screw diameter, lead, required length or stroke, operating speed, axial load, accuracy requirement and shaft-end drawing.
Replacement nut: complete original model, screw diameter and lead, nut dimensions, flange-hole layout and clear product photos.
Unknown model: provide measured dimensions, an existing drawing or a physical sample so the required configuration can be checked before quotation.
Need Help Confirming an SFA Nut?
Send DLY the SFA model, screw diameter, lead, quantity and drawing. For replacement projects, include photos and key dimensions of the existing nut and screw shaft so that compatibility can be checked before quotation.
Hot Tags: sfa nuts, China sfa nuts manufacturers, suppliers, factory, ball nut, DFU Nuts, recirculating ball screw and nut assembly, rotating ball nut design, SCM Nut, ball nuts climbing gear
