Tolerances & Design for Manufacturing — A Practical Guide
The cheapest way to lower a machined part's cost is to design it so it's easy to make. This guide explains what our tolerances mean, where tight tolerance is worth paying for, and the handful of drawing habits that quietly raise your price — so you can decide what actually matters on your part.
What ±0.01 mm means (and where it applies)
±0.01 mm is our standard achievable tolerance on suitable features — not every dimension on every part automatically, but what we hold where the drawing calls for precision. General, non-critical dimensions don't need it, and asking for it everywhere adds cost for no function.
Standard vs. on-request tolerance
We hold ±0.01 mm as standard and ±0.005 mm on request where the feature, material and setup allow. Tighter tolerance means more careful setup, slower cutting, more inspection and sometimes grinding — all real cost. The trick is to specify tight tolerance only on the features that need it and open up the rest.
Surface finish — and what finer costs
Ra 1.6 is our as-machined standard; Ra 0.8 is reachable by fine turning or milling. For sealing and bearing surfaces that need Ra 0.4, we finish on our in-house grinders — centreless for straight round parts up to Ø40 mm, surface grinding for flat faces — so a fine finish doesn't automatically mean an outside vendor and a longer lead time. Specify the finish only where it matters (a sealing land, a bearing seat), not across the whole part.
Five drawing habits that quietly raise your price
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Tight tolerance everywhere
Apply it to the features that need it; open up the rest.
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Sharp internal corners
A tool has a radius; a true sharp internal corner needs EDM or a secondary operation. Allow a corner radius where you can.
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Unnecessary fine finishes
Every step below Ra 1.6 adds time; call fine finish only where function needs it.
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Over-deep pockets & thin walls
Deep, thin features chatter and distort; a small geometry change often cuts cost and risk.
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“Deburr” with no edge-break spec
Say what you mean (e.g. 0.1–0.3 mm edge break) so it isn't left to interpretation.
What to send us for an accurate quote
- A dimensioned drawing (PDF) plus 3D model (STEP or IGES)
- Material and grade
- Quantity
- Required tolerances and finish
- Any inspection/documentation you need
The more precise the input, the more precise — and usually lower — the quote. NDA before quoting on request.