Tolerances that cost you money: when ±0.01 mm is not worth it
Tight tolerances on every feature can double the price of a part. Here is how to decide which features really need them.
Every tolerance on a drawing is an instruction to the machine shop, and the tighter it is, the slower the machining and the more inspection it needs. Many drawings carry a blanket ±0.01 mm that only two or three features actually need.
Tighten only what is functional
- Bearing bores, dowel holes and sealing faces: keep them tight.
- Clearance holes and external profiles: a general tolerance is usually enough.
- Use a title block general tolerance such as ISO 2768-m for everything else.
- Ask your supplier for a DFM review before releasing the drawing.
On a recent housing, relaxing four non-functional tolerances cut machining time by 26% without any change to the part's performance.