Ball Screw
Why choose us
Incoming material and process control:
Shaft material is declared as 20CrMo high-carbon steel, and the thread is formed by cold rolling or precision grinding according to the grade ordered. Each production stage is monitored, and the finished screw and nut are inspected against the size and grade specification before packing.
Tolerance and accuracy verification:
Accuracy grade is a stated positioning error over 300 mm — ±0.01 mm at C5, ±0.02 mm at C7 — so it can be checked rather than trusted. Axial play is taken out by preload, and repeatability is held within ±0.005 mm on the C5 specification.
Matching components and assemblies:
Nut type, grade, lead and end supports are quoted together, because a screw is only as good as what holds its ends. Standard mounting holes at D1/D2/D3 and dimensions interchangeable with mainstream equipment let a replacement drop onto the existing support.
Engineering and quotation response:
Give us the axial load, stroke, speed and whether the axis is vertical, and the reply comes back as a nut, a grade and a size. Enquiries and drawing checks are answered within 24 hours, with urgent requests handled outside that window too.
A ball screw turns motor rotation into straight-line travel with recirculating steel balls rolling between a threaded shaft and the nut, so the axis moves on rolling contact instead of sliding contact. That is what lets a small servo push a heavy table, hold position against a cutting force, and repeat micro-feed moves without stick-slip at reversal. On a CNC router, a press feeder or a pick-and-place head the screw usually sets the positioning accuracy of the whole axis, and two numbers settle most of the argument early: the axial load it has to move, and the tolerance the finished part demands.
How to choose a ball screw: load, accuracy and lead
Nut type and preload
Ball nuts come in single and double versions, and the mounting dimensions are identical apart from length — but a double nut carries more than twice the load of a single one. For medium or heavy load where rigidity and repeatable positioning matter, the double nut is the part to order. Where the application cannot tolerate play at all, the zero-backlash design keeps the balls in full contact with the thread and leaves no gap to open up at reversal.
Accuracy grade, chosen against the work
Grade C7 is enough for general automated equipment, where a positioning error of ±0.02 mm per 300 mm passes inspection. Move up to C5 when the axis is a precision machine tool or a 3C production line: that grade holds ±0.01 mm per 300 mm. C3 is available when the drawing asks for it. Resist buying a higher grade than the part needs — every step up moves the price substantially, and the frame, the feedback system and the assembly routine usually have to follow.
Size from the load
Below about 5 kN, small-lead models such as SFU1605 and SFU2005 do the work. Between 5 and 20 kN, conventional sizes such as SFU2510 and SFU3210 are the sensible pick, and only above 20 kN do large-diameter parts like SFU4010 and SFU5010 start to pay for themselves. The DFU range covers the same ground from DFU1605 up to DFU8010, and the SFE range runs from a 16 mm screw with 16 mm pitch through to 50 mm diameter with 50 mm pitch.
Lead, speed and the vertical axis
High-speed equipment wants a lead of 10 mm or more with a heat dissipation support, because the shaft is turning fast enough for thermal growth to show up in the positioning error. A vertical axis is a separate case: it needs a brake motor plus double-nut preload, so the load cannot fall when the drive is de-energised.
Rolled or ground
Cold rolling forms the thread instead of cutting it, which leaves a smoother surface than a cut thread at a price that suits low and medium load at higher speed — this is what most machines actually run. Precision grinding is the route to the tighter grades, and it is specified for machine tools, semiconductor equipment and measuring axes where the positioning error budget is small.
Ball screw series: SFU, DFU and SFE
| Series | Nut and circulation | Accuracy and load character | Where it fits |
|---|---|---|---|
| SFU | Single-flange nut, internal circulation | C3/C5/C7; C5 holds ±0.01 mm per 300 mm with repeatability within ±0.005 mm; rolling friction about 1/30 of sliding, efficiency above 90%, driving torque about 1/3 of an ordinary screw | CNC machine tools, automation equipment, 3C production lines, laser cutting machines, semiconductor equipment, aerospace positioning axes |
| DFU | Double nut, compact internal circulation | C7 to C5 to C3; double nut carries more than twice the load of a single nut, so it suits medium and heavy load where rigidity and precise positioning are required | High-speed machine tools and machining centres, quick handling systems, general industrial and automation machinery, injection moulding and punching machines, forging machinery |
| SFE | Zero-backlash design, internal and external circulation with end cap and reset hole | No gap between ball and thread, so accuracy and rigidity hold and torque transmits efficiently; screw diameter and pitch from 16 mm to 50 mm | Precision machine tools, robots, aerospace equipment, semiconductor and electronic machinery, laser processing and transfer devices |
Key specs we publish
- ▪C5 grade: positioning error ±0.01 mm over 300 mm with repeatability within ±0.005 mm. On a 1 m axis that accumulates to roughly 0.03 mm of lead error before anything else in the machine contributes.
- ▪C7 grade: ±0.02 mm over 300 mm, the usual starting point for general automated equipment.
- ▪Rolling friction coefficient about 1/30 of a sliding screw, transmission efficiency above 90%, and a driving torque about one third of an ordinary screw at the same thrust — a smaller motor and a cooler nut.
- ▪Shaft material is 20CrMo high-carbon steel; the heavy-duty specification publishes a maximum dynamic load of 662 kN and a static load of 765 kN.
- ▪Supplied with dust-proof seals, and rated for a service life three to five times that of a traditional sliding screw.
- ▪Standard mounting holes (D1/D2/D3) are held to the drawing, so a replacement screw drops onto the support already on the machine.
- ▪Model coverage: SFU1605, SFU2005, SFU2510, SFU3210, SFU4010 and SFU5010; DFU1605 through DFU8010; SFE1616 through SFE5050; a 10 mm ball screw is also listed.
Applications and matching parts
Ball screw axes appear wherever the machine has to reach a position and keep holding it. CNC machine tools and laser cutting machines, 3C electronic production lines with their assembly and test stations, semiconductor equipment, industrial robots, woodworking machines, transfer devices, and the actuator behind an antenna or a valve switch. Heavier duty — all-electric injection moulding machines, punching machines, forging machinery and heavy brakes — goes to the large-diameter ends of the SFU and DFU ranges.
What has to be ordered with the screw
- ▪End supports sized to the shaft journal. A screw is only as straight as what holds its ends, which is why the matching supports are quoted with it.
- ▪The nut version: single nut for light and compact axes, double nut where the axis is vertical or the load is heavy.
- ▪A brake motor for any vertical axis, and a heat dissipation support once the lead goes to 10 mm or more for high-speed duty.
- ▪Dust-proof seals and, on the SFE design, the end cap and reset hole parts that return the balls — these are wear items and worth carrying as spares.
Quality control you can verify
A ball screw is bought on declared numbers, so treat them as something to check rather than something to take on faith. The accuracy grade — C7, C5 or C3 — is a stated positioning error over 300 mm and can be measured on a test bench or on the machine after installation. Shaft material is declared as 20CrMo high-carbon steel, the heavy-duty rating is published at 662 kN dynamic and 765 kN static, and the units leave with dust-proof seals fitted, so the wear path is protected before the first chip arrives. Axial play is removed by preload rather than by hope, and mounting holes are standardised at D1/D2/D3 with nut dimensions interchangeable with mainstream equipment, which is what makes a like-for-like replacement possible without re-machining a bracket.
Send the load, the stroke, the speed and whether the axis stands vertical, and the answer comes back as a nut type, an accuracy grade and a screw size rather than a price for the wrong part. Ordering a ball screw twice from the same drawing should be the easiest item on the purchase list. HLTNC quotes against your duty and keeps the specification on file for the repeat order.