| Tolerances for Holes (ISO 286-2)

The significance of holes in CNC machined parts is equally important as threads. These parts are typically designed to be assembled with other components. When it comes to assembly, the following standard tolerances play a crucial role in determining the relationship between two mating parts. In essence, the “fitting” between the parts can be categorized into three types:

1.transition fitting

A transition fitting, also referred to as a slip or push fit, requires precise alignment and tolerance between mating parts. This type of fitting ensures that the assembly has minimal play or movement, allowing the mating parts to fit together seamlessly.

2. interference fitting

An interference fitting, also known as a press fit, tight fit, or friction fit, is commonly used to secure bearings onto shafts or holes, as well as dowel pins into holes. It can also be employed to assemble spare parts into a single unit, reducing raw material and production costs.

Furthermore, for optimal performance in fixing bearings into holes, burnishing process is often employed to achieve a firm and consistent surface quality. You can refer to Sandy Munro’s comments on the motor of Tesla Model S Plaid at 8’28” for more insights on this topic.

3.slide fitting

A slide fitting, also known as a clearance fit or loose mating, allows the mating parts to slide in and out without any restriction. To optimize the surface quality and ensure smooth sliding between the parts, a grinding process can be employed. This process enhances the overall performance and facilitates unrestricted movement between the mating components.