First, the clearance selection principles:     1, with a tight fit , a larger temperature difference between inner and outer rings , the need to reduce the friction torque and axial deep groove ball bearings to withstand greater load or the need to improve the performance of aligning the occasion , should adopt a large clearance group .
    2, when the high rotation accuracy requirements or to strictly limit the axial displacement , should adopt a small clearance group .
    Second, the clearance -related factors :
    1, with the bearing inner ring and the shaft .
    2 , with the bearing outer ring and housing bore.
    3 , temperature.
    Note: The radial clearance with the mating parts to reduce the amount of the actual size of the effective amount of interference , matching shaft size , wall thickness of the shell hole about .
    1, the actual effective amount of interference ( inner ) should be : △ dy = 2/3 △ d - G * △ d is
    Notional amount of interference , G * to flatten the interference fit size .
    2, the actual effective amount of interference ( outer ) shall be : △ Dy = 2/3 △ D - G * △ D is     Notional amount of interference , G * to flatten the interference fit size .
    3 , the heat generated will cause the internal temperature of the bearing , which in turn causes swelling shaft , bearing and bearing parts. Clearance can increase or decrease , depending on the temperature of the shaft and housing materials , as well as bearings and bearing components between the tonsure .
    Third, the calculated clearance :
    ( 1 ) : with the impact     1 , the bearing inner ring with a solid steel shaft : △ j = △ dy * d / h     2, the bearing inner ring and steel hollow shaft : △ j = △ dy * F (d)     F (d) = d / h * [(d/d1) 2 -1] / [(d/d1) 2 - (d / h) 2]     3 , the bearing outer ring and the steel shell entity : △ A = △ Dy * H / D     4 , the bearing outer ring and steel thin-walled shell : △ A = △ Dy * F (D)     F (D) = H / D * [(F / D) 2 - 1] / [(F / D) 2 - (H / D) 2]     5 , the bearing outer ring and gray cast iron housing : △ A = △ Dy * [F (D) - 0.15]     6 , the bearing outer ring and light metal : △ A = △ Dy * [F (D) - 0.25]     Note: △ j - expanding the amount of wall inner ring raceway diameter (um).     △ dy - journal effective interference (um).      d - bearing bore nominal size (mm).      h - the inner ring raceway wall diameter (mm).      B - bearing width (mm).      d1 - Hollow shaft diameter (mm).     △ A - wall of the outer ring raceway diameter contraction (mm).     △ Dy - housing bore diameter of the real effective amount of interference (um).      H - wall outer ring raceway diameter (mm).      D - bearing outer ring and housing bore nominal diameter (mm).      F - bearing housing outside diameter (mm).
    ( 2 ) : Effect of temperature     △ T = Гb * [De * (T0 - Ta) - di * (Ti - Ta)]     Wherein the coefficient of linear expansion Гb bearing steel as 11.7 * 10-6 mm / mm / 0C     De bearing outer ring raceway diameter , di is the bearing inner ring raceway diameter.
    Ta is the ambient temperature .     T0 is the temperature of the bearing outer ring , Ti bearing inner temperature.     Fourth, the axial clearance and radial clearance of the relationship :
    Ua = [4 (fe + fi - 1) * Dw * Ur - Ur2] 1/2     Ur is small due to the radial clearance , so Ur2 small, negligible .
    The Ua = 2 * [(fe + fi -1) * Dw * Ur] 1/2     Which is the outer groove curvature coefficient fe , fi for the inner groove curvature coefficient , Dw is the ball diameter.