SFE Ball Screw — Large Lead, Single Nut | HLTNC

DFU: two nuts that take the play out

A single-nut screw has to have a little clearance for the balls to run. On an axis that always pushes the same way this never shows; on an axis that reverses under load it shows up as lost position at every reversal, and no amount of tuning the controller removes it.

DFU answers that with a second nut. The two nuts are set against each other on the shaft, so the balls are loaded in both directions and axial play goes to zero. The screw itself is the same as the SFU series - same diameters, same leads, same journals - so a DFU screw drops into a carriage that already takes SFU.

What it costs is length. Two nuts need twice the room: DFU2005-3 is 82 mm long where SFU2005-3 is 42 mm. On a short-travel axis that difference decides whether the series is usable at all, so measure the free length on the screw before specifying it.

Reading the DFU code, and the "/" in the table

The numbers in a DFU code describe one nut, not the pair. DFU3205-3 is a 32 mm shaft with a 5 mm lead, and each of its two nuts has three circuits. The length column is what doubles.

In the table below you will see "/" in some cells where the SFU table has a number. That is the catalogue marking the dimensions where the two nuts are not identical - the front nut and the rear nut have different diameters. Where a single figure is printed, both nuts are the same size and the figure applies to the whole assembly.

The L1 column is the one to read first. A DFU1605-3 is 80 mm of nut on a 16 mm screw, so the nut alone occupies more length than the entire travel of many small axes.

DFU double nut dimensions

DFU models, 16–80 mm (mm)

Reproduced from the manufacturer catalogue, page 26. "/" marks a dimension where the two nuts differ. Load ratings are in kN, per nut, as printed.

Questions we are asked about the DFU series

Is there a preload figure I can design to? The manufacturer does not publish a preload value per model - the nuts are adjusted against each other when they are built. Give us the axial stiffness your axis needs and we will set the pair to suit it.

Will a DFU fit where an SFU already fits? Only the nut length changes. The journals, the bolt pattern and the flange are the same, so if you have the spare length on the screw it is a straight swap.

Does the double nut reduce the load rating? No. Each nut keeps its own rating, and because the pair shares the load in both directions the assembly is stiffer than a single nut. The catalogue lists Ca and Coa per nut.

Which of the five series do you need?

• SFU ball screw - single nut, 12–80 mm
• DFU - double nut, backlash-free - you are on this page
• SFE ball screw - large lead, fast traverse
• SFS ball screw - 12–100 mm, widest range
• SFH / SFA ball screw - precision ground

The question that separates these five is almost always whether the axis reverses under a load. If it does, you want DFU or a preloaded nut; if it does not, the cheapest series that clears the load is the correct answer.

Send us the axis, not just the part number

For a double-nut screw the nut length is the constraint, so tell us the free screw length you have and which direction the axis reverses under load. With that we can confirm whether DFU fits or whether a preloaded single nut would do the same job in less space.

Send an enquiry

Hot Tags: sfe ball screw — large lead, single nut | hltnc, China sfe ball screw — large lead, single nut | hltnc manufacturers, suppliers, factory, hgh linear rail, linear guide for mining equipment, linear guide for rectifier operation, linear guide systems, linear roller way, staf linear guide