What has to be on the drawing?
A datum scheme, the dimensions the assembly depends on with their tolerances, the material and temper, where the wall thickness is measured, the surface finish and treatment, and the acceptance method. Everything else can sit under a general tolerance - that is what keeps tooling effort where it buys function.
Drawing checklist
| Item | Why it matters in the press shop |
|---|---|
| Datum scheme | Decides what is measured against what, and therefore which feature the tool is built around |
| Critical dimensions | The two or three that affect assembly; they get the tight tolerance and the gauging effort |
| General tolerance | Covers everything not called out; avoids tolerancing the whole part tightly |
| Material and temper | Drawability, springback and tooling choice follow from the grade and the temper, not from the geometry alone |
| Wall thickness | State nominal value and the height at which it is measured; a drawn wall thins as it forms |
| Concentricity / coaxiality | Where two diameters have to share an axis, say so explicitly - it drives the die and the inspection |
| Surface finish and treatment | Decides whether the last operation is forming or machining, and whether an external processor is involved |
| Acceptance method | Drawing dimensions, gauge, CMM report or a functional check - agreed before the first article |
Where a 0.001 mm callout is realistic
On selected key machined features - a sealing face, a bearing seat, a ground diameter - and only when the drawing confirms it. A drawn wall is a formed surface: its tolerance is a different order of magnitude by nature of the process, and specifying it like a machined surface makes the part unnecessarily expensive.
If the drawing is incomplete, the DFM review says which dimensions are missing rather than assuming them - send what exists and the application description.