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Preserve the life span of your bearings and the machine

About 17% of premature failures of bearings are due to incorrect installation.

The main causes are:

  • the deterioration caused by installation with poorly adapted methods or tools,
  • over- or under-tightening when adjusting, due to dimensions outside tolerance of shafts and housings,
  • incorrect mounting (too important axial displacement on a tapered seat, pollution etc.).


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  • Check bearing identifying marks against drawings, specifications and procedures.
  • Check that bearing seat dimensions and the accuracy of their shape and position correspond to SNR drawings and specifications.
  • Prepare all equipment, tools and parts required before starting the mounting. Ensure that everything is clean.
  • Carefully clean and check all parts and devices in the bearing's environment.
  • Remove the bearing from its packaging at the last moment in a completely clean working area.
  • Never wash it, except in specified exceptional cases. The bearing is protected from oxidation by a light film of oil compatible with all lubricants.
  • Mount the bearing, using the chosen method.
  • Lubricate, using a special bearing grease, following the instructions given.
  • After mounting and before final start-up, check its operation, so as to detect any possible anomalies (noise, vibrations, temperature, abnormal play, etc.).

The words of an NTN-SNR expert :

For easier mounting and to avoid contact corrosion of the shaft or the housing, always use an anti-fretting paste. This thick lubricant helps preserve the quality of parts surfaces subjected to sliding forces. Without this paste, corrosion will gradually increase the play between the bearing and the shaft (or housing), ultimately causing vibration and even the premature deterioration of the bearing and its mounting surfaces.
Avoid introducing contaminants when mounting (swarf, liquid, etc.).




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 What is cold mounting?


Cold mounting is the simplest method and is suitable for small and medium-sized bearings, completed with the normal adjustments.

The most frequently observed problems

  • Over- or under-tightening when adjusting
  • Excessive impacts during mounting or forces causing rings and seals to break, or races to become indented
  • The accidental introduction of particles or liquids present in the mounting environment


Our recommendations

  • 1st rule: The ring that rotates in relation to the load must be tightly mounted on its seat.



schéma_1_montage_froid  schéma_2_montage_froid Load fixed in relation to the outer ring
Inner ring tightened onto the shaft.
schéma_3_montage_froid  schéma_4_montage_froid Load fixed in relation to the inner ring
Outer ring tightened into its housing.


  • 2nd rule: Mounting is carried out using impact rings applied to the bearing ring which has the tightest fit. This avoids stressing the rotating body and damaging the bearing.


 schéma_5_montage_froid  schéma_6_montage_froid


  • photo_montage_froidSpecial case of a long shaft for an assembly requiring a longitudinal adjustment of the bearing: it is preferable to use a mechanical coupling with a tapered seat joined to a bearing with a tapered bore.




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 What is hot mounting?


  • The mounting of a bearing onto a shaft requires a lot of strength as the size and the fit tolerance increase
  • Heating the bearing before installation allows it to to be inserted without forcing on the shaft
  • NTN-SNR’s induction heaters provide the best solution in terms of safety, cleanliness and speed compared with oil-bath heating, hot plates or ovens.



 huile     Risky           flamme Not permitted

The words of an NTN-SNR expert

  • The temperature must not be too high, so as not to change the characteristics of the steel or the internal components of the bearing (maximum 130°C). On the other hand, it must be sufficient to cause sufficient expansion for the easy installation of the bearing thanks to the temporary loosening.
  • The heating temperature is a function of the size, on the one hand and the fit of the seat on the other.
  • As a general rule, the following temperatures are recommended:


Bore diameter

 Heating temp

 Up to 100 mm  +90°C
 From 100 to 150 mm  +120°C
 Above 150 mm  +130°C


Use of anti-fretting paste
  • facilitates insertion
  • and protects the shaft or housing from contact corrosion

The wearing of heat insulating gloves is necessary for the safe and comfortable handling of the heated parts.
In the case of heavy bearings, help will be required for their handling.

Principle of heating by induction  





  • The device comprises a steel framework surrounded by a coil with a large number of windings. When a current passes through it, this primary coil generates a magnetic field which itself induces an electric current in the bearing (or other steel part), substituted for the secondary coil of an electrical transformer.
  • When a high-intensity, low-voltage AC current passes through it, the bearing heats up quickly while non-metallic parts and the device itself remain cool.
  • Induction heating magnetises the bearing. It is therefore necessary for the heater to demagnetise it at the end of the heating cycle. This avoids steel particles being attracted into the bearing later on.



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 What is hydraulic mounting ?                                            


The mounting of large bearings with a tapered bore requires considerable effort, difficult to achieve using mechanical screw tightening. The use of hydraulic technology is required in such cases.


  • Either an oil film is injected over the whole of the contact surface between the shaft and the inner ring. This reduces the friction generated by the mounting and facilitates tightening.
  • Or the oil is sent at very high pressure into a hydraulic nut which develops the thrust required for the mounting.
  • The two principles may also be used simultaneously to make mounting easier. The residual clearance is checked using feeler gauges or a comparator which measures the embedding on the tapered contact surface.

Two types of mounting lend themselves to this method:




Tapered seat shafts  



Injection of an oil film



Use of a hydraulic nut alone


Shafts with a cylindrical contact surface in association with a sleeve



 Withdrawal sleeve


  Adapter sleeve 


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