Rod end bearings / Spherical bearings -Sleeve Bearing
Sleeve Bearing
Sleeve Bearing life is a function of the load, oscillation angle, velocity, contamination, shaft surface finish, and hardness influence the life expectation of sleeve bearings. Teflon lined sleeves are recommended to be used under slow velocity oscillation of less than 10~20cpm.
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
Surface rughness | Life Factors |
---|---|
less than 0.2μmRa | 1 |
0.2μmRa ~ 0.4μmRa | 0.75 |
0.4μmRa ~ 0.8μmRa | 0.4 |
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
Hardness | Life Factors |
---|---|
50HRC and harder | 1 |
50 ~ 40HRC | 0.6 |
40 ~ 30HRC | 0.4 |
Figure 14: Teflon 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
X-1118 X-1276 X-1276F |
X-1820 | ||
---|---|---|---|
Static Limit Load | Alumimum | 345N/mm^{2} { 35.2kgf/mm^{2} } | 345N/mm^{2} { 35.2kgf/mm^{2} } |
Steel | 413N/mm^{2} { 42.2kgf/mm^{2} } | 482N/mm^{2} { 49.2kgf/mm^{2} } | |
Oscillation Load | 172N/mm^{2} { 17.6kgf/mm^{2} } | 258N/mm^{2} { 26.4kgf/mm^{2} } |