Description

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An SFU ball screw uses a standard flanged single nut to convert rotary motion into accurate and efficient linear travel. The flange provides a practical connection between the nut and the moving table, while the recirculating steel balls reduce sliding friction between the screw shaft and nut.

DLY supplies C7 rolled SFU ball screws for general CNC and automation applications, with C5 ground versions available when higher positioning accuracy is required. Standard components use an S55C screw shaft, a 20CrMo nut and hardened raceway surfaces of HRC 58–62.

The available range covers nominal diameters from 12 to 100 mm and leads from 4 to 20 mm. Screw length, shaft-end machining, thread direction and support-unit configuration can be produced according to the installation drawing. More structural options are available in the DLY ball screw range.

Standard Process： C7 cold rolled

Precision Option： C5 ground

Diameter Range： 12–100 mm

Lead Range： 4–20 mm

Nut Structure： Flanged single nut

SFU Structure

The SFU series combines a threaded screw shaft with a flanged recirculating ball nut. As the shaft or nut rotates, the balls roll through the loaded raceway and return through the circulation path inside the nut assembly. This rolling contact reduces friction and required drive torque compared with a sliding screw mechanism.

The nut flange connects directly to the moving component through its mounting holes. Because the flange dimensions, nut length and circuit configuration vary by model, the complete model number should be confirmed instead of selecting only by nominal diameter and lead.

Efficient Transmission：Rolling contact reduces friction and helps convert motor rotation into smooth linear travel.

Standard Flange： The nut flange provides a straightforward mounting interface for machine tables and nut housings.

Multiple Circuits： Three-, four- and selected six-circuit configurations are available according to model and load requirement.

Custom Assembly： Screw length and both shaft ends can be machined to match bearings, motor couplings and support units.

Technical Data

Item	Specification
Product series	SFU ball screw
Nut structure	Standard flanged single nut
Screw shaft material	S55C
Ball nut material	20CrMo
Raceway hardness	HRC 58–62
Standard manufacturing process	Cold rolled ball screw
Accuracy	C7 standard; C5 ground version optional
Nominal diameter	12, 16, 20, 25, 32, 40, 50, 63, 80 and 100 mm
Lead	4, 5, 6, 10 and 20 mm, depending on diameter
Thread direction	Right-hand standard; left-hand optional
End machining	Machined according to drawing or matching support-unit dimensions
Matching support units	BK/BF, FK/FF and EK/EF series; large sizes confirmed by shaft-end drawing
Supply format	Screw and nut assembly, machined assembly or component supply
Warranty	12 months

Dimensions

The drawing defines the principal SFU nut dimensions used in the specification table. All dimensions are in millimetres. Ca and Coa are listed in kgf, while stiffness K is expressed in kgf/μm.

Dimension symbols: d = nominal screw diameter; l = lead; Da = ball diameter; D = nut outside diameter; A = flange outside diameter; B = flange thickness; L = nut length; W = flange width; X = mounting-hole diameter; H = mounting-hole centre distance; Q = mounting thread; N = number of circuits.

Models with the same diameter and lead may use different ball diameters, nut lengths or numbers of circuits. These differences affect the nut dimensions, dynamic load, static load and rigidity. Confirm the complete suffix when replacing an existing ball screw.

Model	d (mm)	Lead (mm)	Da (mm)	D (mm)	A (mm)	L (mm)	W (mm)	N	Ca (kgf)	Coa (kgf)	K (kgf/μm)
SFU1204-4	12	4	2.381	24/22	40	40	32	4	593	1129	12.5
SFU1604-4	16	4	2.381	28	48	40	38	4	629	1270	35
SFU1605-3	16	5	3.175	28	48	43	38	3	765	1240	17
SFU1605-4	16	5	3.175	28	48	50	38	4	780	1790	20
SFU1610-3/2	16	10	3.175	28	48	47	38	3	721	1249	15
SFU2005-3	20	5	3.175	36	58	43	47	3	860	1710	22
SFU2005-4	20	5	3.175	36	58	51	47	4	1130	2380	25
SFU2010-3/2	20	10	3.175	36	58	47	47	3	830	1680	20
SFU2505-3	25	5	3.175	40	63	43	51	3	980	2300	32
SFU2505-4	25	5	3.175	40	63	51	51	4	1280	3110	35
SFU2510-4	25	10	4.762	40	63	85	51	4	1944	3877	33
SFU2510-4/2	25	10	3.175	40	63	54	51	4	1150	2950	30
SFU3205-4	32	5	3.175	50	81	52	65	4	1450	4150	40
SFU3206-4	32	6	3.175	50	81	57	65	4	1720	4298	43
SFU3210-4	32	10	6.35	50	81	90	65	4	3390	7170	45
SFU4005-4	40	5	3.175	63	93	55	78	4	1610	5330	49
SFU4010-4	40	10	6.35	63	93	93	78	4	3910	9520	55
SFU5005-4	50	5	5.175	75	110	55	93	4	1730	6763	60
SFU5010-4	50	10	6.35	75	110	93	93	4	4450	12500	65
SFU5020-4	50	20	7.144	75	110	138	93	4	4644	14327	59.5
SFU6310-4	63	10	6.35	90	125	98	108	4	5070	16600	80
SFU6320-4	63	20	9.525	95	135	149	115	4	7573	23860	84.1
SFU8010-4	80	10	6.35	105	145	98	125	4	5620	21300	90
SFU8010-6	80	10	6.35	105	145	118	125	6	7810	31800	106
SFU8020-4	80	20	9.525	125	165	154	145	4	8485	30895	108
SFU10020-4	100	20	9.525	150	202	180	170	4	9420	39183	134

Load ratings and stiffness values vary with ball diameter, number of circuits and nut configuration. Final selection should also consider working load, acceleration, speed, stroke, mounting orientation, expected service life and screw-shaft critical speed.

Model Code

SFU 20 05 - 4

Series | Nominal diameter | Lead | Number of circuits

SFU: standard flanged single-nut series.
20: nominal screw diameter of 20 mm.
05: lead of 5 mm per screw revolution.
4: four ball circulation circuits.

Some models include an additional designation such as "3/2" or "4/2". The complete suffix identifies the specific ball and circulation configuration and should not be omitted when checking nut dimensions or replacing an existing assembly.

Diameter and Lead

Diameter and lead perform different functions in selection. The nominal diameter is mainly related to axial load, rigidity, unsupported length and critical speed. The lead determines the linear distance travelled for each screw revolution.

Selection Item	Smaller Value	Larger Value
Screw diameter	Lower moving mass and smaller installation envelope	Greater axial rigidity and improved resistance to buckling
Lead	More motor revolutions for the same travel; finer mechanical movement per revolution	More linear travel per revolution and potentially higher linear speed
Number of circuits	Shorter nut and lower load capacity within comparable designs	Longer nut with increased load capacity and rigidity

A high lead does not automatically mean that the assembly can run at any required speed. Maximum operating speed must still be checked against shaft length, support method, critical speed, ball circulation and lubrication conditions.

Accuracy Options

C7 Rolled SFU Ball Screw Suitable for general CNC auxiliary axes, automation equipment, packaging machines, handling systems and linear modules where reliable transmission and repeatable travel are required.

C5 Ground SFU Ball Screw Available for applications with higher lead-accuracy requirements. Manufacturing feasibility should be confirmed according to diameter, lead, length and shaft-end drawing.

Accuracy grade describes the lead accuracy of the screw assembly. It does not by itself determine positioning performance. Bearing arrangement, axial clearance, nut preload, thermal expansion, mounting alignment, coupling accuracy and machine rigidity also affect the final result.

End Machining

SFU screw shafts can be supplied without end machining or machined according to the customer's drawing. A complete shaft-end drawing defines the bearing seats, retaining features and motor connection more reliably than specifying only the overall screw length.

Bearing Seats：Fixed-side and supported-side bearing diameters and tolerances.

Retaining Threads：External threads for locknuts and bearing retention.

Motor Connection：Coupling diameter, flat, keyway or other drive-end feature.

Centre Holes：Machining and inspection features when required by the drawing.

When an existing ball screw is being replaced, provide the complete shaft drawing or measure every stepped diameter, length, thread and keyway. Overall length alone is not sufficient for direct installation.

Support Units

The machined shaft ends can be matched with standard fixed-side and supported-side bearing units. The support-unit series should be selected together with the shaft-end dimensions rather than added after the screw has been machined.

Support Pair	Mounting Form	Typical Use
BK / BF	Square fixed and supported units	Machine frames, CNC axes and general automation structures
FK / FF	Round flange fixed and supported units	Flange-mounted structures and compact bearing-seat arrangements
EK / EF	Compact square fixed and supported units	Smaller screw diameters and space-controlled assemblies

For 50–100 mm screw diameters, the required bearing arrangement and support housing should be confirmed from the actual axial load, shaft-end diameter and installation drawing.

Applications

CNC Machines： Feed axes, auxiliary positioning axes, drilling equipment and machining fixtures.

Automation Equipment： Assembly stations, transfer units, lifting mechanisms and positioning tables.

Packaging Machinery： Filling, sealing, labelling, cutting and format-adjustment mechanisms.

Linear Modules： Motor-driven linear axes combined with guide rails, support units and couplings.

Selection Information

For model confirmation and shaft-end design, provide the following operating information:

Nominal diameter and lead, or the current complete model number
Required screw length, effective thread length and travel
Horizontal, vertical or inclined mounting orientation
Working load, peak load, speed and acceleration
Required accuracy grade and axial-clearance requirement
Fixed-side and supported-side bearing arrangement
Motor coupling dimensions and complete shaft-end drawing
Operating environment, lubrication and contamination conditions

FAQ

Q: What does SFU1605 mean?

A: SFU identifies the flanged single-nut series. The number 16 indicates a nominal screw diameter of 16 mm, while 05 indicates a lead of 5 mm per revolution. The circuit suffix should also be confirmed because SFU1605-3 and SFU1605-4 have different nut lengths and load ratings.

Q: Is the SFU ball screw supplied in C5 or C7 accuracy?

A: C7 cold-rolled construction is the standard option for the SFU series. A C5 ground ball screw can be produced when higher lead accuracy is required, subject to confirmation of diameter, lead, length and production feasibility.

Q: Can DLY machine both ends of the screw shaft?

A: Yes. Both shaft ends can be machined according to a drawing, including bearing seats, retaining threads, coupling diameters, flats and keyways. The drawing should include dimensions, tolerances and thread specifications.

Q: Can SFU ball screws be supplied with BK and BF supports?

A: Yes. BK/BF, FK/FF and EK/EF support-unit configurations are available for suitable shaft diameters. The screw ends must be machined to match the selected bearing units.

Q: Is a larger lead always better for high-speed movement?

A: A larger lead produces more linear travel per motor revolution, but maximum speed also depends on screw length, rotational speed, support method, critical speed, lubrication and ball circulation. Lead should be selected together with the complete drive design.

Q: Can a left-hand SFU ball screw be produced?

A: Right-hand thread is the standard configuration. A left-hand screw can be produced for suitable specifications when the thread direction is clearly marked on the drawing and confirmed before production.