Key principles.
Simple
Plus-minus from nominal. Easy to specify. Less flexible.
Functional
Position, profile, runout. Functional fit verification.
Default
Default tolerance class. -m (medium) common. -f (fine) tighter.
Cpk > 1.33
Process capability. Cpk > 1.33 capable. Production verifies.
Springback
Aluminum springs back. Steel stable. Plastic creeps.
Worst case vs RSS
Worst case (additive) vs root-sum-square (statistical).
FAQ
Functional fit critical. Bearing bores, mating features. ASME Y14.5 standard.
ISO 2768-m (medium) covers most. Tighter only on critical features.
±0.005 mm requires grinding/lapping. ±0.025 mm CNC capable. Below 0.005 specialty.
Multiple parts mating. Worst case = sum. RSS = √(sum of squares). RSS more realistic at production.
5-10× cost premium per tighter class. Don't over-specify. Default loose, specify tight per function.
Note on drawing: "All tolerances per ISO 2768-m unless noted." Explicit tolerances override.
Get an instant quote
Send your CAD — we reply with detailed pricing, lead time, and DFM feedback within 4 working hours.
Talk to an engineer
WhatsApp our team directly. Most messages answered within 12 minutes during work hours.
Explore all services
CNC, 3D printing, injection molding, sheet metal, casting, finishing — one quality system, one partner.
Working on a live project? Send the STEP file and the two or three features you are unsure about — an engineer replies with DFM notes and a price, usually within four working hours.