Vague requests get vague quotes — and parts that don't quite fit. Whether you have full drawings or just an old part, here's what to include so a supplier can quote accurately and make it right the first time.
The ideal package
- A drawing or 3D model (STEP, IGES, STL) — or a sample/photo if you don't have one
- Key dimensions, and which ones are critical
- Tolerances — how much variation is acceptable
- Material grade, or the operating environment so they can recommend one
- Surface finish or treatment requirements
- Quantity and target lead time
- Any certifications required
If you have CAD files
Common formats manufacturers accept include STEP, IGES, STL, SLDPRT, and 2D PDF drawings. If possible, send both a 3D model and a dimensioned 2D drawing — the 2D drawing carries tolerances and critical callouts the 3D model alone does not.
If you only have a sample or photo
Send the physical part if you can; otherwise photograph it clearly with a scale reference and list every dimension you can measure. A capable manufacturer can reverse-engineer the part from there.
Why tolerances matter
Tolerance is how much a dimension can vary and still work. Tighter tolerances cost more and take longer; looser tolerances are cheaper. Specify tight tolerances only where the part actually needs them — over-specifying raises cost for no benefit.
Don't forget the operating environment
Telling the supplier where and how the part works — temperature, corrosion exposure, pressure, vibration — lets them recommend the right material and treatment. That is often more useful than dictating a grade you're unsure about.
Frequently asked questions
What CAD format is best?
STEP is the most universal 3D format; pair it with a 2D PDF drawing for tolerances.
What if I don't know the material?
Describe the operating environment; a good supplier will recommend a suitable grade.
Do I need to specify tolerances?
For critical dimensions, yes. For the rest, standard tolerances are usually fine.
Related reading
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