The invention discloses a method for measuring the axial clearance or the preload clearance of back-to-back angular contact ball bearings, which comprises the steps of firstly manufacturing an outer ring spacer bush (4), a
gasket (1), an inner
diameter load block (7) and a measurement
system and then correcting measurement instruments, wherein the inner ring (2) of a bearing I is arranged on the
gasket, the bearing I and a bearing II are arranged on the outer ring spacer bush back to back, the inner
diameter load block is arranged in the inner ring (6) of the bearing II; and during the correction of instruments, one end of each of the two equilong levers, which is provided with a right-angle measuring head, extend into an inner ring space bush through each notch groove of the inner ring spacer bush. During the measurement, the inner
diameter load block of a balance weight applies
axial load to the bearing I and the bearing II, the two right-angle measuring heads respectively align to the center points A and B of the bearing I and the bearing II, wherein A-B=
delta, if the
delta is a negative value, the bearing I and the bearing II are in axial clearance, and if the
delta is a positive value, the bearing I and the bearing II are in preload clearance. The invention has the advantages of simple operation, no complicated conversion for obtaining measurement result, visually readable values A and B, and
no conversion and cumulative errors.