Sleeve Bearing

Shaft surface finish

Shaft roughness is specified to be 0.2μmRa or less. Please refer to Table 13, when shaft surface is rougher than 0.2μmRa for life factor.

Table 13 : Life factors for roughness of shaft

Shaft hardness

50HRC or harder is the standard shaft hardness. Table 14 shows the life factors which shall be taken into an account when shaft hardness is lower than 50HRC. Figure 14 shows the surface pressure and life cycle at which the wear does not exceed 0.152mm, under oscillation angle ± 25° and frequency 10 cpm.

Table 14 : Life factors for hardness of shaft

Figure 14: PTFE type sleeve stress & life

Definitions for Sleeve Bearing Terminology

Static Limit Load

This is the load at which permanent set does not exceed 0.102mm.

Oscillation Load

With Minebea standard items, wear should not exceed 0.152mm after 25,000 cycles, oscillation angle of ± 25° at a frequency of 10 cpm. Load capacity can be calculated as the race projected areas (S) multiplied by the allowable stress (σ) (Figure 15).

Figure 15: Sleeve

Projected area (S)

The projected area can be calculated as:
Straight S = B (L - 2.54)
Flange S = B × { (L + F) - 3.3 }
Only when sleeve length (L) is bigger than bore (B), shaft bending shall be taken into consideration.
When projected area S is bigger than B2, B2 value is used for projected area S.

Allowable stress (σ)

Table 15 shows the allowable stress.

Table 15 : Allowable Stress of Sleeve Bearings