CNC Machining Tolerance Grades
How tight should your tolerances be? Compare the four common grades by typical process, application and cost.
Standard Tolerance CNC Machining
Standard tolerance is the default ISO 2768 medium grade for general-purpose machined parts. It is the most economical CNC tolerance and suitable for non-critical features, brackets, enclosures, and decorative components where mating fit and alignment are not driven by tight dimensional control.
Cost: 1.0× (baseline)
Machined Tolerance CNC Machining
Machined tolerance (±0.025 mm / ±0.001") is the standard CNC tolerance for functional parts that need consistent fit and alignment. It is achievable on virtually any modern CNC machine with proper tooling, fixturing, and inspection. This is the default specification for industrial parts unless tighter tolerances are explicitly required.
Cost: 1.2–1.5×
Precision CNC Machining Tolerance
Precision tolerance (±0.005 mm / ±0.0002") is reserved for critical functional features such as bearing seats, fluid sealing diameters, alignment dowels, and optical mounting surfaces. It requires high-rigidity machine tools, climate-controlled shops, sharp tooling, and CMM verification on every part.
Cost: 2.0–3.0×
Ultra-Precision CNC & Wire EDM Tolerance
Ultra-precision tolerance (±0.003 mm / ±0.0001") is at the limit of subtractive manufacturing without resorting to grinding or lapping. It is achieved primarily through wire EDM, jig grinding, and ultra-precision turning on temperature-stabilized machines. Surface finishes typically reach Ra 0.1 µm or better.
Cost: 4.0–6.0×
Our shop machines metal parts to 0.02 mm. See also our tolerance chart.