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Shaft and housing geometry

In general, machining bearing seats and shoulders in spindles and housings requires careful consideration. The tolerances to which these characteristics should be held are dependant upon the class, size and application of the bearing. In general, these tolerances should be no greater than the total indicator runout (TIR) of the assembled bearing.

● Accuracy of form and position for bearing seatings on shafts and in housings

● ISO tolerance grades for dimensions (lengths, widths, diameters etc.)

Nominal
dimension 		Tolerance grades
IT1 IT2 IT3 IT4 IT5 IT6 IT7 IT8 IT9 IT10 IT11 IT12
over
mm 		incl max
μm
3 6 1 1.5 2.5 4 5 8 12 18 30 48 75 120
6 10 1 1.5 2.5 4 6 9 15 22 36 58 90 150
10 18 1.2 2 3 5 8 11 18 27 43 70 110 180
18 30 1.5 2.5 4 6 9 13 21 33 52 84 130 210
30 50 1.5 2.5 4 7 11 16 25 39 62 100 160 220
50 80 2 3 5 8 13 19 30 46 74 120 190 300
80 120 2.5 4 6 10 15 22 35 54 87 140 220 350
120 180 3.5 5 8 12 18 25 40 63 100 160 250 400

● Guideline values for surface roughness of bearing seatings

Diameter of seatings
d(D)1)

Recommended Ra value for ground seatings
( Roughness grade numbers ) Diameter tolerance to
over incl IT1 IT2 IT3
mm μm
3 80 1,6 (N7) 0,8 (N6) 0,4 (N5)
80 500 1,6 (N7) 1,6 (N7) 0,8 (N6)

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