Protect fit and function without adding unnecessary machining time, inspection cost or supplier risk.
A blanket ±0.01 mm tolerance may look precise, but it can make a straightforward equipment part slower and more expensive to manufacture without improving how the machine works.
A better drawing identifies the features that locate, guide, seal, rotate or align. These features receive the control the assembly actually needs; non-critical dimensions follow a practical general tolerance.
Before assigning a number, consider what happens if the feature is slightly larger, smaller or out of position. Does a shaft bind? Does a bearing move? Does a bracket fail to align with another module? Or does nothing meaningful change?
A plus/minus dimension is not always the clearest way to protect an assembly relationship.
Define the intended clearance, transition or interference fit and identify the mating feature.
Use clear datums and positional control when several holes must align with a mating plate.
Flatness, parallelism and perpendicularity may matter more than overall part length.
Surface finish, flatness and edge condition should reflect the gasket, O-ring or fluid path.
Closer limits reduce the acceptable process window. The supplier may need another finishing pass, different setup, grinding, controlled temperature, special fixturing or more capable inspection.
Quantity matters too. A demanding one-off prototype and a repeat order of 500 pieces require different process-control decisions.
Use the surfaces or axes that locate the part in the real assembly, not merely a convenient drawing origin.
Highlight fits, positions and faces that affect performance. Use a sensible general tolerance note elsewhere.
Do not dimension the same feature in conflicting ways. Use geometric controls when the relationship requires them.
Coating thickness, surface roughness, deburring and edge breaks can change final size and assembly fit.
Agree which characteristics must be recorded and which may be verified during normal in-process inspection. A full report for every drawing dimension is not always the most useful requirement.
Send the drawing and explain the part's function. HONMET can flag quotation questions and discuss a practical manufacturing and inspection route before pricing.
Upload Your Drawing →This guide provides general build-to-print sourcing guidance. Final tolerance, process and inspection decisions remain subject to drawing, material, geometry, application and quantity review.
