Sheet Metal Drawing Callouts: What a Buyer Should Put on the File
A drawing is the contract between your spec and the built part. This guide lists the callouts a buyer should include — material, tolerances, bends, hardware, finish — so the quote matches the part and first-article inspection has something to measure against.
Specify the must-haves
Over-calling every dimension slows the quote and raises cost; under-calling leaves the fit to chance. Mark what is tight, free the rest.
Leave the rest to shop
Over-calling every dimension slows the quote and raises cost; under-calling leaves the fit to chance. Mark what is tight, free the rest.
Hand FAI a target
Over-calling every dimension slows the quote and raises cost; under-calling leaves the fit to chance. Mark what is tight, free the rest.
What to put on the drawing
| Callout | Why it matters | Links to |
|---|---|---|
| Material and thickness | Grade and gauge of every panel; the single biggest cost and fit driver. | BOM, quotation, FAI |
| Critical dimensions and tolerances | Which sizes are tight (sealing, assembly) vs free; default shop tolerance elsewhere. | Tolerances guide, FAI |
| Bend radii and notes | Preferred radius, grain direction if it matters, and any relief callouts. | DFM guide, flat pattern |
| Hardware and inserts | PEM-style inserts, rivnuts, hinges and gaskets by part number where possible. | Hardware guide, assembly |
| Finish and marking | Coating type, colour (RAL), and any silk-screen or label callouts. | Surface finishes, QA |
Only mark what is tight
Call out the dimensions that affect sealing, assembly or function; let the shop apply its standard tolerance elsewhere. Read the enclosure tolerances guide and the DFM design rules so your tight callouts are the ones that matter.
Make the flat pattern unambiguous
- State bend radius and direction
- Note grain direction only when it affects strength
- Reference the flat-pattern and bend-deduction method
- Show hardware by part number, not just "insert"
Close the loop on inspection
Name the finish and colour so the quote and the part agree, and give inspection a target in first-article inspection. Our quality process measures against the callouts you provide.
Who reads the drawing right
A supplier that quotes from the drawing (not a guess) returns the part you specified. See how to choose a supplier and keep the spec tight with the RFQ checklist.
Get a quotationDrawing callouts
At minimum: material and thickness, the overall dimensions, the tight tolerances that affect fit or sealing, bend radii, any inserts or hardware by reference, and the finish and colour. Anything not called out should fall back to the shop standard, not to a guess.
No. Tolerance only the dimensions that matter — holes that mate, seams that seal, parts that assemble. Over-tolerancing every size forces tighter, slower, costlier work on dimensions that do not need it and can actually hide the ones that do.
State the bend radius and direction, and note grain direction only when it affects strength or appearance. Reference the flat-pattern method (bend deduction or K-factor) so the supplier unfolds the part the same way you expect; see the flat-pattern guide.
First-article inspection measures the built part against the drawing's callouts. If the drawing is vague, inspection has nothing to hold the part to and the supplier fills the gaps — which is how good quotes turn into wrong parts.
Send the file, get a quote from the drawing
CAD or PDF with the callouts above — we quote from the spec and release volume against first-article inspection.