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Precision lock nuts with locking pins

Precision lock nuts with locking pins

SKF precision lock nuts were originally developed for use with precision bearings (fig 1) and their dimensions were chosen accordingly.

SKF precision lock nuts are available in two designs:

  • KMT lock nuts (fig 2) are designed as slotted nuts and the smaller sizes up to and including size 15 are also produced with two diametrically opposed flats to take spanners. They are intended for applications where high precision, simple assembly and reliable locking are required.
  • KMTA lock nuts (fig 3) have a different external shape from that of KMT nuts and in part a different thread pitch. They have a cylindrical outside surface and are primarily intended for applications where space is limited. As the outside surface is cylindrical the nut can also be used to form part of a gap-type seal. Holes around the circumference and in one side face facilitate mounting.

Precision lock nuts have three locking pins equally spaced around the circumference. These pins are pressed against the shaft by grub screws and prevent the nut from turning. The locking pins and grub screws are arranged at the same angle to the shaft as that of the thread flanks (fig 4). The ends of the pins are machined with the nut thread and as a result also have a threaded profile. As the locking pins are not deformed, the nuts retain their high precision irrespective of the frequency with which they are mounted and dismounted. Additional locking washers or keyways in the shaft are not needed.

Precision lock nuts are adjustable. The three equally spaced locking pins enable the nut to be accurately positioned at right angles to the shaft or they can be used to adjust for inaccuracies or deviations of other components which are to be located on the shaft.


Bearing accessories | Adapter sleeves | Withdrawal sleeves | Lock nuts | Lock nuts with locking washer or clip | Lock nuts with locking screw | Lock nuts with integral locking device | Precision lock nuts with locking pins | Hydraulic nuts