Bushings, or plain bearings, operate with sliding motion between the moving surfaces. Bushings are selected based on the rotating speed and the applied load. Most bushings do not require additional lubrication to operate. In this blog post we’ll look at what bearing users need to know about tolerances in wrapped and non-wrapped (standard) bushings.
Wrapped Bushings Tolerances
It is not possible to accurately measure the external and internal diameters of a wrapped bushing in its free condition. In the free state, a wrapped bushing will not be perfectly cylindrical. The bushing will conform to the housing when the split is tightly closed. For this reason the OD & ID of a wrapped bushing can only be checked with special gauges and test equipment.
Below is an example on how to determine the bushing’s ID & OD tolerances with respect to the mating shaft and housing tolerances after installation:
The chart and diagram shows that after installation this bushing will have a total OD tolerance of 0.030 mm. Also, the ID tolerance is 0.065 mm after installation.
Standard Bushings (Non-Wrapped) Tolerances
Standard bushing tolerances are specified on their respective dimension tables. For example:
If a bushing with an 8 mm ID (d) and a 12 mm OD (D*) is used, the ID (d*) dimension specifies an F7 tolerance which corresponds to 13 µm / 28 µm. The OD (D) dimension specifies an m6 tolerance which corresponds to 7 µm / 18 µm.
*Note: Uppercase tolerances refer to different values from lowercase tolerances
Bushings Online Catalog
AST Bearings’ comprehensive bushings catalog contains detailed specifications and 3D CAD models for 3,278 different bushings in 12 categories. Click here to go to our online catalog and product specifier for all of our metal bushing bearings including free 3D CAD model downloads.
Selecting the right bushing for each project requires detailed knowledge of the application requirements and experience with bushing technology. AST’s bearing experts are available to help with advice and guidance to make the selection process as easy as possible. Our bearing experts and engineers are ready to help, contact them here.