Description

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Product Overview

An SFU ball screw uses a flanged single nut and recirculating steel balls to convert rotary motion into linear travel, replacing the sliding friction of a lead screw with rolling contact. The flange bolts directly to the moving table or nut housing. DLY manufactures the series as standard stock items and as machined assemblies made to your drawing.

Technical Advantages

· Shaft: S55C steel, induction hardened.

· Nut: 20CrMo, carburized to a hardness of HRC 58–62.

· Balls: G10-grade steel balls.

· Accuracy: cold-rolled C7 and C10 are the standard grades, manufactured to GB/T 17587. C5 ground versions are available on request, subject to diameter, lead and length.

· Circuits: 3-, 4- and 6-circuit nuts, matched to the load requirement.

Hardness must stay inside the specified range, because values outside it increase the risk of shaft fracture. DLY engineers name quenching and tempering as the process they take most pride in.

Specifications

Nominal diameters: 12, 16, 20, 25, 32, 40, 50, 63 and 80 mm. Dimensions are in mm, Ca and Coa in kgf, and stiffness K in kgf/μm.

Model	d	Lead	Da	D	A	L	W	N	Ca	Coa	K
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
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

Symbols: d = nominal diameter; Lead = lead per revolution; Da = ball diameter; D = nut outside diameter; A = flange outside diameter; L = nut length; W = flange width; N = number of circuits; Ca = basic dynamic load rating; Coa = basic static load rating; K = stiffness.

Models with the same diameter and lead can differ in ball diameter, nut length and circuits, which changes the dimensions, load ratings and rigidity. Always quote the complete model number.

Model code: SFU 20 05 - 4

· SFU: flanged single-nut series

· 20: nominal diameter, 20 mm

· 05: lead, 5 mm per revolution

· 4: number of ball circuits

Some models carry an extra suffix such as 3/2 or 4/2. It identifies the circulation configuration and must be kept in the model code when checking nut dimensions.

Selection and Replacement

1. Diameter relates to axial load, rigidity, unsupported length and critical speed.

2. Lead sets the linear travel per revolution. A larger lead does not mean a higher usable speed, which also depends on screw length, support method, ball circulation and lubrication.

3. Circuits: more circuits give a longer nut with a higher load rating.

The two most common selection mistakes are choosing the wrong lead and the wrong support arrangement.

Replacing an existing screw: DLY mounting dimensions match the original model. Check three items: outside diameter, length and mounting-hole positions. Send the old model number, drawing, old part or photos, plus the equipment type and working condition.

Custom Machining and OEM

Standard customization: screw length and shaft ends are machined to your drawing. End forms include BK/BF, FK/FF and EK/EF support ends, keyways, flats, internal threads and hex ends. Shaft-end machining typically takes 5–15 days, depending on quantity.

Non-standard products: non-standard leads and nuts are made at a minimum order of 100 pieces, in 20–30 days, with pricing based on the drawing.

OEM: laser-marked logos, custom packaging, colors and labels.

Applications

· CNC engraving machines

· Woodworking machinery

· Packaging equipment

· Automatic loading and unloading

· Laser equipment

For axes where positioning accuracy is critical, ask about the C5 ground option.

Why Choose DLY

Stock and samples.
Standard models are supplied from stock, typically in 7–30 days depending on order quantity. Orders start from 1 piece, and free samples are available.

Direct replacement.
Mounting dimensions follow the original model, and DLY engineers confirm the match from an old model number, drawing or photos.

Long and custom screws.
Screws up to 9 m long can be machined to your shaft-end drawing, and physical custom samples are available for review.
Verifiable quality.
Factory inspection covers lead error, travel variation, thread and raceway, runout and concentricity, straightness, hardness, axial clearance, appearance and dimensions, using a lead measuring instrument, coordinate measuring machine and hardness tester. Inspection is first-article plus patrol, reports include a dimension table, and life, noise and temperature-rise tests run on an in-house test bench.

About the Manufacturer

Zhejiang DLY Automation Manufacturing Co., Ltd. is a manufacturer, not a trading company, founded in 2005 with 20+ years of manufacturing experience. The plant in Lishui, Zhejiang covers 30,000 m²+ and employs 200+ people, including 20 in R&D and 25 in quality inspection. DLY holds 60+ patents and produces 40,000 m of ball screws and 40,000 nuts per month. The company is a National High-Tech Enterprise.

The quality management system is certified to ISO 9001 (valid until 25 September 2027) for the production of ball screw assemblies, linear guideways and cylindrical linear shafts.

Most key processes are in-house: cold rolling, screw heat treatment, thread grinding, nut raceway and internal thread grinding, ball selection, assembly and inspection. Nut heat treatment is outsourced and steel balls are purchased.

Address: No.12, Baixian Road, Shuige Industrial Zone, Lishui, Zhejiang, China.

Packaging, Shipping and Terms

· Packaging: shaft ends protected with sleeves, surface wrapped, nut secured; long or heavy items in wooden cases. Products ship greased and rust-protected, with grease nipples and end plugs included.

· Shipping: sea freight (LCL) is common; FOB Ningbo or Shanghai.

· Payment: T/T, 30% deposit and 70% before shipment, in USD or RMB.

· Warranty: 12 months.

FAQ

Q: Should I choose C7 or C5 for an SFU ball screw?

A: C7 cold-rolled is the standard grade for general power transmission. C5 ground is intended for positioning duty where tighter lead accuracy is required, and DLY confirms feasibility by diameter, lead and length. Accuracy grade describes lead accuracy only. Final positioning performance also depends on bearing arrangement, axial clearance, thermal expansion, alignment, coupling accuracy and machine rigidity.

Q: Which support arrangement should I use?

A: Fixed–fixed, fixed–supported and fixed–free arrangements are used. Fixed–fixed gives the highest rigidity and the longest unsupported length, fixed–free suits only short screws at low speed, and fixed–supported falls between. The final choice depends on screw length, speed, load and bearing layout.

Q: How should I store and handle a long SFU ball screw?

A: A long screw bends under its own length when unsupported. Support it along its length on wooden boards, and use a wooden case for transport, as DLY does when shipping long screws.

Q: What do I need to send for shaft-end machining?

A: Send a complete shaft-end drawing with dimensions, tolerances and thread specifications for bearing seats, coupling diameter, flats, keyways, internal threads or hex ends. When copying an old screw, measure every stepped diameter, length, thread and keyway. Overall length alone is not enough.

Q: How can I check quality before shipment?

A: Product photos, packing photos or a short inspection video can be provided on request, and the packing list can include an inspection certificate.

Q: What happens if there is a problem after delivery?

A: Keep the product, packaging and labels, and send photos or video, the order number and a description of the problem. DLY engineers assess whether the cause lies in selection, installation alignment, lubrication, overload or contamination.