For Linear actuators, a common mechanism is to use ballscrews with ballnuts.

The ballscrew is supported at the two sides by a set of bearings which permit the rotation of the screw while keeping the axial reaction force to the ballnut movement.

Looking for those ballscrew supports, I found there are several categories:

  • Floating (identified by F)
  • Fixed (Identified by K)

An other letter indicate several types/shapes of supports: E, B, F, etc.

Those pieces are usually sold in a set of one fixed and one floating support:






I could not find understandable information about this.

What types of ballscrew/leadscrew supports exits? What is the difference between them?


2 Answers 2


As you see, you use one fixed and one floating bearing to compensate for stress due to thermal expansion of the rod, manufacturing or assembly tolerances.

Floating bearing can’t take axial loads, where fixed bearings take both axial and radial loads.

I guess the letters e, b, f specify the mounting type, for example

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But to be sure you have to provide a datasheet or link

  • $\begingroup$ What about the first letter? B/E/F? $\endgroup$ Nov 15, 2017 at 7:45

BK, BF refer to the mount format - in this case a rectangular face mounted block with one (BF) or two (BK) bearings and mount holes.

1st Letter == mount format; 2nd letter == bearing set ; numeric == ID of the bearings in mm;

A quick internet search will identify all of these bearing types and specifications. F series face mounted

E series base mount

B series heavy duty


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