Patent ID: 7594759

Claim:
A method of imparting a preload to first and second ball bearings, which are each an oblique contact double row ball bearing, and said first and second ball bearings are axially arranged to have preload applied simultaneously thereto, the method comprising: providing said first ball bearing with first bearing first and second rows of balls wherein said first bearing first row of balls have a first bearing first pitch diameter and a first radial clearance α 1 , and said first bearing second row of balls have a first bearing second pitch diameter and a second radial clearance β 1 , wherein said first bearing first pitch diameter is greater than said first bearing second pitch diameter and said first radial clearance α 1 is greater than said second radial clearance β 1 ; providing said second ball bearing with second bearing first and second rows of balls wherein said second bearing first row of balls have a second bearing first pitch diameter and a first radial clearance α 2 , and said second bearing second row of balls have a second bearing second pitch diameter and a second radial clearance β 2 , wherein said second bearing first pitch diameter is less than said second bearing second pitch diameter and said first radial clearance α 2 is greater than said second radial clearance β 2 ; arranging said first and second ball bearings on a common shaft to disposed sequentially said first bearing first row of balls, said first bearing second row of balls, said second bearing first row of balls, and said second bearing second row of balls; rotating said common shaft; measuring a rotation torque of said shaft; applying and increasing preload to said first and second bearings while measuring said rotation torque until a measured rotation torque enters a predetermined range such that: inner and outer raceways of said first bearing second row of balls are first fitted to said first bearing second row of balls to generate rotation torque and subsequently inner and outer raceways of said first bearing first row of balls are then fitted to said first bearing first row of balls to generate further rotation torque; and inner and outer raceways of said second bearing second row of balls are first fitted to said second bearing second row of balls to generate rotation torque and subsequently inner and outer raceways of said second bearing first row of balls are then fitted to said second bearing first row of balls to generate further rotation torque.