August 17,2026
Excessive interference between a rolling bearing and its shaft or housing can cause cracks or even fracture of the inner or outer ring. Therefore, the limit interference fit must be verified during assembly.
The tensile strength of GCr15 is not specified in national standards, industry standards, or specialized monographs. The following values, compiled from various sources, are provided for reference only:
A critical point to note regarding the tensile strength of GCr15 steel is that its value is highly dependent on the heat treatment condition. Therefore, when consulting standards, it is essential to distinguish between the "annealed (as-supplied) state" and the "quenched and tempered (final service) state."
Annealed state (as-supplied): According to national standards, the tensile strength of GCr15 in the annealed condition is typically ≥ 861 MPa. In this state, the material has lower hardness and is primarily intended for subsequent machining and cold forming.
Quenched and tempered state (final service): After heat treatment (typically oil quenching from about 840 °C followed by low-temperature tempering at about 160 °C), the tensile strength of GCr15 increases significantly, with typical values in the range of 1800–2200 MPa. This represents the actual strength level of bearing components in service.
The tensile strength of quenched bearing steel is approximately 1600–2000 MPa. It can be said that the above timax is within the permissible range. However, for safety, it is generally considered advisable that the maximum circumferential stress should not exceed 130 MPa. If this value is adopted as the criterion, then the limit interference fit between the bearing and the inner ring is: 80% of *d*/1000 is the safe upper limit.
When the inner ring is mounted with an interference fit, internal stresses are generated, namely radial stress σrand circumferential stress σt.
2.1.1 Radial stress σr in the inner ring
The maximum radial stress in the inner ring occurs on the bore surface and appears as compressive stress.
2.1.2 Circumferential stress σr in the inner ring
The maximum circumferential stress in the inner ring occurs on the bore surface and appears as tensile stress.
The circumferential stress in the inner ring is greater than the radial stress.
2.2 Outer Ring–Housing Interference Fit
When the outer ring is mounted with an interference fit, internal stresses are generated, namely radial stress σr and circumferential stress σr.
2.2.1 Radial stress σr in the outer ring
The maximum radial stress in the outer ring occurs on the outer diameter surface and appears as compressive stress.
2.2.2 Circumferential stress σr in the outer ring
The maximum circumferential stress in the outer ring occurs on the outer diameter surface and appears as compressive stress.
The circumferential stress in the outer ring is greater than the radial stress.
Example: Bearing 6206, De = 56.038 mm, di = 36.975 mm, d = 30 mm, D = 62 mm, μ = 0.3, E = 206,900 MPa. The shaft is solid, and the housing outer diameter is 80 mm. Both the shaft and housing materials are steel.
Suppose the interference between the inner ring and the shaft is 0.030 mm.
Inner ring radial compressive stress: 35 MPa;
Circumferential tensile stress: 171 MPa (exceeds 130 MPa; it is recommended to reduce the interference).
Suppose the interference between the inner ring and the shaft is 0.022 mm.
Inner ring radial compressive stress: 25.9 MPa;
Inner ring circumferential tensile stress: 125.8 MPa
Suppose the interference between the outer ring and the housing is 0.062 mm.
Outer ring radial compressive stress: 14.8 MPa;
Outer ring circumferential compressive stress: 162 MPa (exceeds 130 MPa; it is recommended to reduce the interference).
Suppose the interference between the outer ring and the housing is 0.048 mm.
Outer ring radial compressive stress: 11 MPa;
Outer ring circumferential compressive stress: 125 MPa.
