SFU & DFU Series - 4mm to 10mm Lead, for CNC, 3D Printing, and Light-to-Medium Automation

DLY's 16mm diameter ball screw is available across multiple series to suit different installation and performance requirements. The most widely specified options are the SFU series (single nut, flanged) and DFU series (double nut, flanged, zero-backlash) - covering 4mm, 5mm, and 10mm lead configurations for CNC routers, 3D printers, engraving machines, and general automation axes.

SFU1605 / SFU1604 / SFU1610-Single Nut, Flanged, 16mm Diameter

The SFU series uses a single nut with end-cap ball recirculation and a flanged mounting interface. It is the standard configuration for most 16mm ball screw applications where backlash within normal tolerance is acceptable.

SFU Specification table for ball screw set

Model	Lead	Ball Dia.	Circuits	Ca (kgf)	Coa (kgf)	Stiffness K (kgf/μm)
SFU1604-4	4mm	2.381mm	4	629	1,270	35
SFU1605-3	5mm	3.175mm	3	765	1,240	17
SFU1605-4	5mm	3.175mm	4	780	1,790	20
SFU1610-3/2	10mm	3.175mm	3	721	1,249	15

How to choose between these four:

SFU1605-4 has the highest dynamic load rating, 780 kgf, and the highest stiffness among the standard-circuit options. It is the default recommendation for most 16mm axes unless a specific lead or budget constraint applies.
SFU1604-4 offers the finest lead, 4mm, for applications prioritizing positioning resolution over speed, though its dynamic load rating, 629 kgf, is the lowest in this diameter.
SFU1605-3 is a lighter-duty, lower-cost option at the same 5mm lead, suited to applications where SFU1605-4's full load capacity is not required.
SFU1610-3/2 provides double the linear speed of SFU1605 for the same motor RPM, at a moderately lower load rating, 721 kgf. It is the choice when axis speed is the priority.

DFU1605 / DFU1604 / DFU1610- Double Nut, Flanged, Zero Backlash

The DFU series uses the same lead and load rating specifications as SFU at each configuration, but with a double-nut preloaded design that eliminates axial backlash. This is the choice when direction-reversal accuracy matters - CNC machining axes, precision positioning systems, or any application where the SFU's standard backlash would affect part quality or repeatability.

DFU Specification table for ball screw set

Model	Lead	Ball Dia.	Circuits	Ca (kgf)	Coa (kgf)	Stiffness K (kgf/μm)
DFU1604-4	4mm	2.381mm	4	629	1,270	42
DFU1605-3	5mm	3.175mm	3	765	1,240	30
DFU1605-4	5mm	3.175mm	4	780	1,790	43
DFU1610-3/2	10mm	3.175mm	3	721	1,249	28

The key difference from SFU is not load capacity - it's stiffness and backlash. At every matching lead and circuit configuration, DFU's Ca and Coa ratings are identical to SFU. What changes is the K value. DFU1605-4 reaches 43 kgf/μm compared to SFU1605-4's 20 kgf/μm, because the double-nut preload removes internal clearance and increases axial rigidity.

The dynamic load rating measures how much load the ball circuit can sustain over its rated life. It does not capture backlash or stiffness, which is why these figures are the same across SFU and DFU at the same configuration. Choose DFU over SFU when the axis reverses direction frequently and positioning accuracy at the reversal point matters, or when maximum axial stiffness is required. The trade-off is higher running friction and a longer nut body compared to the equivalent SFU configuration.

SFU vs DFU at a Glance

Item	SFU Single Nut	DFU Double Nut
Backlash	Standard clearance present	Eliminated through preload
Stiffness	Standard	Up to 2× higher, depending on configuration
Nut Length	Shorter	Longer
Running Friction	Lower	Slightly higher
Cost	Lower	Higher
Best For	General CNC, 3D printing, automation	Precision CNC, reversing axes, high-rigidity requirements

Other 16mm-Compatible Series

Beyond SFU and DFU, DLY produces several other 16mm diameter ball screw series for applications with specific installation, circulation, or speed requirements. These share similar load ratings to SFU/DFU at matching lead configurations, with the key differences summarized below.

SFI - Single Nut, Internal Circulation, Flanged
Uses an internal ball return path instead of an external end cap, producing a more compact nut body. Suited to installations where radial space around the nut is limited. Load ratings match SFU at equivalent lead and circuit configuration.

DFI - Double Nut, Internal Circulation, Flanged
The internal-circulation equivalent of DFU - zero backlash with a compact nut profile. Choose this over DFU when both zero backlash and reduced installation diameter are required simultaneously.

SCI - Internal Circulation, No Flange
A non-flanged version using internal circulation, for installations where the nut is secured by a separate housing rather than a direct flange mount. Useful in custom nut housing designs or where flange bolt access is restricted.

SCM - No Flange, External Thread Mount
Mounts via an external thread on the nut body, such as M27×1.5P for the 5mm-lead version, rather than a flange. This series has a notably lower load rating in its lightest configuration - SCM1604-3 rates at only 435 kgf Ca - making it suited to lighter-duty applications where simpler thread-mount installation is preferred over flange mounting. Standard DLY nuts in this series ship without seals unless specified.

SFE - Large Lead Series
SFE is not a direct alternative to SFU/DFU for standard applications. At 16mm diameter, it is built around 16mm and 32mm leads, not 4–10mm, and is designed for high-speed axes where rapid linear travel matters more than fine positioning resolution. Available in 3-circuit and 6-circuit versions, such as SFE1616-3 at 650 kgf Ca and SFE1616-6 at 1,180 kgf Ca. Consider SFE only when the application specifically requires high-speed operation beyond what a 10mm-lead SFU1610 provides.

Material and Precision

All DLY 16mm ball screws are manufactured from GCr15 bearing steel, with the shaft raceway induction hardened for wear resistance and load capacity. Standard precision is C7 rolled; C5 ground is available on request for applications requiring tighter positioning accuracy.

Typical Applications

CNC routers and engraving machines, especially X/Y axis drive
3D printer Z-axis and gantry drives
Small-format laser cutting machines
Light-to-medium duty pick-and-place automation
General workshop and woodworking machinery

For Z-axis or vertical installations, confirm whether your selected lead requires a motor brake. Leads above approximately 10mm can back-drive under load when the motor is de-energized.

Custom Lengths and End Machining

Standard and custom shaft lengths are available, with end machining to your drawing or DLY's standard configurations, including threaded end, stepped end for bearing mounting, flat, or keyway as required.

If you do not have a formal drawing, share your required length and end specifications, and DLY will confirm before production.

FAQ

Q1: What are the common lead options for a 16mm ball screw?

For standard SFU and DFU 16mm ball screws, common lead options include 4mm, 5mm, and 10mm. A 4mm lead is suitable for finer positioning resolution, 5mm is a balanced choice for many CNC and automation axes, and 10mm is selected when higher linear speed is required.

Q2: What is the difference between SFU and DFU 16mm ball screws?

SFU is a single-nut flanged ball screw for general motion applications. DFU uses a double-nut preloaded structure to reduce axial backlash and increase stiffness, making it more suitable for reversing axes, precision CNC equipment, and applications where positioning repeatability is more important.

Q3: Should I choose SFU1605, SFU1604, or SFU1610?

SFU1605 is the most common balanced option for many 16mm axes. SFU1604 is better when positioning resolution is more important than speed. SFU1610 provides faster linear movement at the same motor speed and is suitable when axis speed is the priority.

Q4: When should I choose DFU instead of SFU?

Choose DFU when the axis changes direction frequently and backlash at the reversal point may affect accuracy. DFU is also suitable when higher axial stiffness is required. Compared with SFU, DFU has a longer nut body and slightly higher running friction.

Q5: Can DLY supply other 16mm ball screw series besides SFU and DFU?

Yes. DLY can supply SFI, DFI, SCI, SCM, and SFE series for different installation and speed requirements. SFI and DFI are suitable for more compact internal-circulation structures, SCI is used without a flange, SCM uses external thread mounting, and SFE is designed for large-lead high-speed applications.

Q6: What precision grades are available for DLY 16mm ball screws?

DLY can supply C7 rolled ball screws for most CNC routers, 3D printers, engraving machines, and general automation systems. C5 ground ball screws are available on request for applications requiring tighter positioning accuracy.

Q7: Can the ball screw length and end machining be customized?

Yes. DLY can provide standard or custom shaft lengths with end machining according to your drawing. Common end machining includes threaded ends, stepped bearing seats, flats, keyways, and motor connection ends.

Q8: Is a 16mm ball screw suitable for vertical Z-axis use?

Yes, but the lead and load should be checked carefully. For vertical axes, especially when using larger leads such as 10mm or above, confirm whether a motor brake is needed to prevent back-driving when the motor is de-energized.

Q9: What information is needed for a 16mm ball screw quotation?

Please provide the series, lead, total length, end machining drawing, precision grade, quantity, and application. If you are replacing an existing screw, photos or the original model number can help confirm the specification faster.