Manufacturing Tolerances
Tolerance is the acceptance range that defines how far a manufactured dimension may vary from its nominal design value.
Definition
Tolerance is the acceptable range around a part's nominal dimension. For example, 10.00 ±0.10 mm accepts results from 9.90 through 10.10 mm. Every process, material, and geometry has a different accuracy level that it can achieve economically.
Related Terms
- DFM: checks whether tolerances are realistic for the selected process and geometry.
- CNC: a subtractive process capable of precise dimensions through controlled toolpaths.
- FDM: an additive process affected by orientation, layer height, and shrinkage.
- SLA: a fine-detail process that can be affected by resin behavior and post-curing.
Common Uses
Tolerances manage shaft-and-hole fits, clearance between moving parts, assembly alignment, and sealing surfaces. Mark critical dimensions clearly on a drawing and avoid applying unnecessary precision to cosmetic-only surfaces.
Watchouts
"As precise as possible" is not a measurable requirement. Supply the nominal dimension, lower and upper limits, measurement method, and functional purpose together. Tighter tolerance usually means higher price and longer lead time because it adds operations, inspection, and scrap risk.