Call on 01202 339559

GRW High Precision Ball Bearings

High precision ball bearings in grades up to ABEC 9 with bores from 1 to 30mm and comparable inch dimensions

WHY NOT TRY OUR BEARING SELECTOR - CLICK HERE

Inch/Metric Bearing
Tolerance:
Desired Bore
Desired Outer Diameter
Material
Type
Closure

limiting speeds

The maximum speed for a ball bearing in operation is limited by various mechanical and kinematic criteria. Narrow tolerances of bearings and surrounding parts, special measures regarding lubrication and type of lubricant as well as special retainer materials and designs generally have a beneficial effect on the speed limit. The characteristical values for speed given in the tables only apply to specially set reference conditions. They therefore only give an indication of the relative speed suitability of the ball bearing. Please call us for more information if operating conditions are different.

The kinematically permissible speed nzul

The ‘kinematically permissible speed nzul’ applies to ball bearings with contact seals which do not have a thermal reference speed nur defined in the standard. It takes into consideration the special conditions resulting from the wiping contact between ball bearing inner ring and seals. In principle the same conditions as for the thermal reference speed nur otherwise apply.

The thermal reference speed nur

The reference conditions have been selected in DIN 732-1 so that the ‘thermal reference speed nur’ is identical for both types of lubrication: oil or grease. The essential operating conditions are:

  • Reference temperature of the ball bearing on stationery outer ring 70oC
  • Reference temperature of the ball bearing environment 20oC
  • Reference loading P, of the ball bearing 5% of the static radial loading rating Cor
  • Oil lubrication as oil bath lubrication with a conventional mineral oil without EP additives, with a kinematic viscosity of 12 mm2/s at 70oC
  • Grease lubrication with a standard lithium soap grease with a mineral base oil without EP additives. The kinematic viscosity of the base oil is 22 mm2/s at 70oC. The grease quantity is approx. 30% of the free space in the ball bearing
  • Ball bearings with standard designs, i.e. with standard accuracy, with standard radial play, with non-contact closures
  • Ball bearing installed on a horizontal shaft with a stationery outer ring and installation dimensions and tolerances which do not reduce bearing radial clearance

The permissible thermal operating speed n

The speed at which the average ball bearing temperature reaches the permissible value in real operating conditions is called the ‘permissible thermal operating speed nu’. It is calculated from the thermal reference speed by multiplying it with the factor ‘speed ration fn’ according to DIN 732-2: nu = fn . nur

Following the standard we use diagrams which make calculating this factor far easier. The different torque effects of oil and grease lubrication are taken into consideration. 

Click on image to enlarge 

  Figure 6: Calculation of the permissible thermal operating speed nu

 

Product By Industry

Today we serve a broad band of industry with a wide range of quality products.

Need a technical question answered?