When custom parts go wrong, unclear drawing annotations are the cause eight times out of ten. Here are the details most often missed.
When ordering custom motor parts to drawing, the completeness of the drawing determines whether the finished part is usable. The following are most often omitted.
Datums and tolerances. Geometric tolerances need explicit datums, otherwise the machinist can only judge by experience. For mating dimensions, specify the tolerance band rather than just the nominal size.
Material and heat treatment. The same dimension in different materials performs very differently. If heat treatment or surface treatment is involved, specify the method and hardness requirements.
Surface requirements. Roughness, coating type and film thickness should be annotated together, especially for explosion-proof or outdoor applications.
Quantity and batch. For a first order, run a small batch to verify assembly before committing to volume — an effective way to reduce risk.
Annotating these details on the drawing and supplementing with a physical sample or photos significantly improves the success rate of custom parts.
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