Bearing Clamping Force

All bearings, angular contact or radial, need to be locked in place. This can be done with a precision nut, bolt pattern on a face/mounting plate, or other application specific means. A few key points of this clamping force are:

  • Proper clamping procedure
  • Not exceeding GMN recommended maximum forces
  • Establishing enough of a clamping force to achieve proper engagement
  • Tight tolerancing

Recommended Clamping Procedure

Lightly oil the precision nut or bolt thread. Thread locker is considered the same as ‘oil’ when applied to thread. Light is key; the thread should not be 100% covered with thread locker. Install by hand and tighten the nut 2-3 times past the goal torque with an accurate torque wrench. Then back the nut off and retighten to the goal torque.

Note that the 2-3 times tightening ensures proper seating of the bearing, nut, and other associated parts. This part of the procedure also insures that any thread imperfections do not hinder proper resultant clamping force.

Recommended Clamping Forces

The table below outlines the GMN Recommended clamping forces. Note that these forces are based on a safety factor below the plastic deformation of the bearing race cross section of the AISI 52100 bearing material. It is known that these numbers may seem high, but they should be used as a maximum or something to get close to. A clamping force that is too low can be just as detrimental to bearing life as a force that is too high. Too low of a clamping force would be defined as being close to the Factory Pre-Load of the bearing (i.e. L/M/S Newton values).

Click to see full table...
Bore DiameterBore CodeRecommended Clamping Force (kN)**Specific to stated thread only**
Tighten Torque (Nm)Thread
618...619...60...62...618...619...60...62...
55-0.60.70.8-0.40.50.6M 5 x 0.5
66-0.80.81.4-0.70.71.3M 6 x 0.5
77-0.91.11.6-0.81.21.6M 7 x 0.5
88-0.91.3--11.5-M 8 x 0.75
99-11.41.9-1.31.92.6M 9 x 0.75
10011.11.62.11.41.62.33.1M 10 x 0.75
1211.11.21.62.31.722.74.1M 12 x 1
1521.31.522.42.634.25M 15 x 1
1731.41.82.433.23.95.57M 17 x 1
2042.22.43.14.25.66.48.315M 20 x 1
2552.53.13.84.78.2151520M 25 x 1.5
30633.14.5615152025M 30 x 1.5
3573.14.15815202540M 35 x 1.5
4083.44.66.5920253550M 40 x 1.5
459-5.57.59.5-304560M 45 x 1.5
5010-4.7810-305065M 50 x 1.5
5511-61012-457590M 55 x 2
6012-61116-4585120M 60 x 2
6513-61119-5095160M 65 x 2
7014-913--80120-M 70 x 2
7515-9.513--90130-M 75 x 2
8016-9.516--95170-M 80 x 2
8517-1317--140180-M 85 x 2
9018-1319--150220-M 90 x 2
9519-1320--160240-M 95 x 2
10020-1620--210260-M 100 x 2
10521-1722--220300-M 105 x 2
11022-1726--230360-M 110 x 2
12024-2127--310410-M 120 x 2

Clamping Force for Proper Engagement

Each application may have its own specifics that will affect the required clamping force. Using the GMN recommended clamping forces will remove most of these variables. However, a heavy press fit, differing materials, special coatings, etc. should be taken into account. The clamping force and clamping apparatus needs to achieve a fully seated bearing. This is the goal, but it can be achieved in various ways. Please consult GMN USA engineering if technical support is needed.

A properly seated bearing is contacting all of the mating abutments and the races are axially aligned.

Mating Part Tolerancing

Tolerancing of all surfaces that influence the bearings is very important. An incorrect tolerance stack up could potentially fully seat a bearing without actually pre-loading the bearing. Conversely, the opposite can happen and the bearing could be over loaded. Both of these incorrect scenarios can equally reduce bearing life by large amounts. A thorough axial tolerance stack up is required for all applications to insure proper bearing pre-load (i.e. MMC/LMC analysis). A spring pre-load does allow more tolerance flexibility, but be sure to not change the target force with too large tolerance window(s). Please consult GMN USA bearing engineering to support tolerance establishment. GMN USA Engineers can also be a consult on the effects of varying tolerances on bearing life.

  • 'Big O' Arrangement
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    S
    • Simple example utilizing a mounted flange on either end of the spindle to establish bearing pre-load while also potentially protecting the bearing(s) from contamination. A common ‘Big O’ arrangement is shown with a single bearing on each end of the spindle.
  • 'Big X' Arrangement
    S
    S
    • Simple example utilizing a mounted flange on either end of the spindle to establish bearing pre-load while also potentially protecting the bearing(s) from contamination. A common ‘Big X’ arrangement is shown with a single bearing on each end of the spindle.
  • 'Big O' Alternate Arrangement
    S
    S
    • Simple example utilizing precision nuts to pre-load the bearings. A common ‘Big O’ arrangement is shown with a single bearing on each end of the spindle.
  • 'Big X' Alternate Arrangement
    S
    S
    • Simple example utilizing precision nuts to pre-load the bearings. A common ‘Big X’ arrangement is shown with a single bearing on each end of the spindle.

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