How We Calculated This
This calculator uses three factors to estimate how tolerance affects CNC machining cost: a tolerance multiplier, a material difficulty factor, and a complexity factor. The three are multiplied together to give a combined cost impact.
Tolerance Multiplier
The tolerance multiplier reflects how much extra time and care each tolerance level requires. At ±0.010″, the machine runs at normal speed with standard tooling. This is the 1.0x baseline. As tolerance tightens, the machine must run slower, take lighter cuts, and make more finishing passes. At ±0.0005″, the multiplier reaches 5.0x because the part often needs a temperature-controlled environment and 100% CMM inspection.
Material Difficulty Factor
Some materials are harder to hold tight tolerances on. Aluminum 6061-T6 machines predictably with low tool deflection, so its factor is 1.0. Stainless Steel 304 work-hardens and generates more heat, pushing the factor to 1.4. Titanium Ti-6Al-4V has high strength and low thermal conductivity, making it 2.2x harder to hold tight tolerances compared to aluminum.
Complexity Factor
Simple parts with few features are easy to hold to tolerance. Complex parts with thin walls, deep pockets, and many features are harder because of vibration, tool deflection, and thermal distortion. A complex part adds a 1.5x factor on top of the other multipliers.
Estimated Cost Range
The cost range uses a baseline of $35 per part for a simple Aluminum 6061-T6 part at ±0.010″. The combined multiplier is applied to this baseline. The range accounts for variation in part size, geometry, and shop rates.
Pro tip: Use GD&T to apply tight tolerances only where they matter. A drawing with ±0.005″ general tolerance and ±0.001″ on two critical bores costs far less than a drawing with ±0.001″ on every dimension.