What Is The Difference between A Single-nut And A Double-nut Ball Screw?

What is the difference between a single-nut and a double-nut ball screw?

Ball screw single nut and double nut have the following differences:

1. Structure and Installation

Single nut: consists of one nut, simple structure, relatively small installation dimensions, short total length of the nut. 

Double nut: consists of two nuts, preload is applied by rotating the two nuts in opposite directions.

2. Preload

The nut is secured by pins installed between them. The installation dimensions are the same as those of a single nut, except that the length is twice as long.

3. Performance features

Load capacity: The load-bearing capacity of double nuts is greater than that of single nuts, usually more than twice that of single nuts, capable of withstanding larger axial and radial forces.

Stiffness: Double nuts can increase stiffness through preload, better resisting deformation and maintaining motion stability; single nuts have relatively lower stiffness.

Accuracy: Double nuts can eliminate axial clearance, improving positioning accuracy and repeatability, making them suitable for high-precision applications; single nuts may have slight axial clearance in practical use, but can still meet certain precision requirements through strict control and preload.

Lifespan: The lifespan of double nuts is typically longer than that of single nuts because they can better withstand loads and reduce wear.

4. Application scenario

Single nut: suitable for small equipment, fast transmission speed, and occasions where precision requirements are not high, such as small CNC machining equipment, semiconductor production equipment, assembly robots, and measuring instruments.

Double nut: suitable for machinery requiring high stiffness and precise positioning under moderate or heavy loads, such as large CNC machines, industrial robots, aerospace equipment, etc.

5. Cost and maintenance

Cost: The single nut structure is simple, so the cost is relatively low; the double nut, due to its complex structure, usually has a higher price than the single nut.

Maintenance: Dual nuts are more convenient for later maintenance, as the clearance can be controlled by adjusting the thickness of the shims to regulate the preload of the lead screw, eliminating lead screw clearance; single nuts tend to develop clearance after several years of use, and it is difficult to eliminate the clearance through adjustment.

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