Engineering Resource

What a tight tolerance requires

• A machine rigid and accurate enough to cut the feature without deflection.
• Sharp tooling at the right geometry, replaced before wear reaches the tolerance.
• Fixturing that holds the part without deforming it.
• Thermal control, because the part and the machine both move with temperature.
• Measurement capable of resolving a fraction of the tolerance.

Temperature is the quiet variable

Steel expands roughly 12 µm per metre per °C; aluminium about twice that; plastics far more. A part cut warm and measured warm can read perfectly and be out of tolerance at rest. Tight work is therefore machined with heat controlled and measured in a stable environment — and stress-sensitive parts are measured only after they have relaxed.

Process capability, not luck

A tolerance is only held if the process produces conforming parts repeatedly, not if one part happens to pass. That is why tight work uses stable parameters, predictable tool life and a measurement loop that feeds back into the process rather than sitting at the end of it.

Where the limit is

We hold ±0.005 mm on 3-axis work and ±0.01 mm as standard on simultaneous 5-axis, verified on a Zeiss CMM. Tighter than that stops being a machining question and becomes a metrology and cost question — worth discussing before the drawing is frozen, not after.