Reducing Tolerances

Bronze Bushing

There are many design situations where it is tempting (and easier) to just specify a tighter tolerance. For example:

• A slip fit of a shaft and bushing
• A press fit of a rod to a hole
• Precise alignment of mating parts
• etc.

Since tighter tolerances are more expensive to manufacture, the smart designer will often use tricks to avoid tight tolerances. Here are a few such techniques:

• Machine a clamp into a part to allow to retain a shaft by tightening a screw.
• Retain a shaft with a set screw instead of a press fit.
• Use shim washers to tune spacing.
• Order parts with slightly under sized holes and ream after receiving the parts.
• Use over sized holes to reduce alignment issues.
• Use stock precision bushing inserts.