Kappa – Lambda Enhanced Viscosity Required by Bearing Type (update)

The following data given below is for the various bearing types listed and is very approximate. It gives the minimum oil viscosities at operating temperature when the Mean Bearing Diameter is multiplied by the Rpm (DmN) and is within the range of ≈10000 DmN to ≈400000 DmN.  Bf refers to the Bearing Factor and is the approximate amount that the viscosity has to be increased for the proper oil film thickness generated by the basic Kappa – Lambda formulas based on bearing type.

The following lists bearing types and their minimum viscosity when using simple lubrication (mineral oil only.) It is possible to go below the listed viscosity, but enhanced additives are required to lubricate properly.  (Otherwise the point contact pressure becomes high enough to "punch through" the oil film.)
              
1.0 - Ball bearings

• Mfg01 (Note 1) = 13.2 cSt (centistokes)
• Mfg02 = 13 cSt
• OR-D (Note 2) says Bf = 1 (Base Line)

2.0 - Cylindrical roller bearings

• Mfg01 = 13.2 cSt to 20 cSt (Bf = 1.52) - depending on the cage of the bearing
• Mfg02 = 20 (Bf = 1.53)
• OR-D says Bf = 1.63 (6.5 / 4) see below

3.0 - Spherical (self-aligning), needle (with a cage) and tapered roller bearings

• Mfg01 = 20 cSt (Bf = 1.52)
• Mfg02 = 20 cSt (Bf = 1.53)
• OR-D says Bf = 1.63 (6.5 /4)

4.0 - Spherical (self-aligning) roller thrust bearings and needle bearings without a cage

• Mfg01 = 33 cSt (Bf = 2.5)
• Mfg02 = 30 cSt (Bf = 2.3)
• OR-D = There were no values for these classifications.

(Note 1) – Mfg01 & Mfg02 = Refers to Bearing Manufacturers Number 01 and 02
(Note 2) – OR-D = Other Research and Development

A further delineation came from OR-D where they gave the minimum C/P ratios for standard oil as follows.

• C/P > 4.0 for Ball Bearings.
• C/P > 6.5 for Roller Bearings (Hence 13/8 = 1.625, see above.)
• C/P > 10.5 for spherical thrust bearings, needle bearings without a cage.
• For very high angle tapered roller bearings use C/P ≈ > 6.5 + 4.0[Tan(roller angle with shaft)].

Svenska Kullagerfabriken AB (SKF) data from the early 1960-1970’s also showed approximately the same differentiation by bearing type (values were not quite the same as listed below). After considerable research, the following was concluded and used internally by Vanair Enterprises for the value of “Bf” in the EHL formulas.  This may or may not be the values used by the bearing industry to determine viscosity by bearing type.  However, Vanair has used these values quite successively for many years with Lambda and only recently with Kappa.

k or Λ (enhanced viscosity) ≈ Bf * k or Λ (base viscosity) 

Where Bf (Bearing factor) is equal to >>>  

• 1.00 for ball bearings.
• 1.63 for roller bearings, tapered roller bearings, and needle bearings with a cage.                     
• 2.64 for spherical thrust bearings and needle bearings without a cage.
• For very high angle tapered roller bearings use (1.64) + Tan (roller angle with shaft).