A good metal part drawing gets a real quote on the first reply. A poor one gets a list of questions. Since 1999, our Nanpi factory has built 70,000+ different part types. The good news: most drawings fail for the same five reasons. This guide lists what to include, line by line. Then it shows how we check what you send. Read it once; fix your template once.
The Seven Lines Every Drawing Needs
- Views: at least one orthographic, or a STEP file.
- Overall dimensions: length, width, height of the part.
- Hole data: diameter, position, depth, edge distance.
- Bend lines: location and inside radius.
- Material and thickness: the grade, not just “metal”.
- Finish: coating, plating or bare, stated.
- Quantity: per order, and per year if known.
A metal part drawing is a contract, not a sketch. Seven lines, one reply. Missing any of them turns a quote into an interview. The interview is free, but it takes days. Every line above is one our check asks for.
File Formats That Work
| Format | Best for | Notes |
|---|---|---|
| STEP | 3D parts | Our default; no bend ambiguity |
| DXF | Flat parts | Fast for laser and simple bends |
| DWG | Existing CAD shops | Works; STEP is cleaner |
| PDF, fully dimensioned | Simple parts | Only if every dimension is on it |
Send the file your designer actually used. Screenshots lose hidden faces. A photo of a screen loses the units. The rest of the vocabulary is on our sheet metal terminology page.
Tolerances: Mark the Two Kinds
- General tolerance: state one default for the whole part.
- Critical dimensions: mark them, and give the real number.
- Do not mark everything critical; inspection cost scales with it.
- Fit-related features are the usual critical set.
Our defaults are public. The sheet metal tolerances post lists what we hold by process. If your drawing carries no tolerance at all, we apply the default and say so in the quote. Silence is a decision; we make it visible.
Material and Bend Notes
- Name the grade: 304, 316, 6061, cold-rolled steel.
- Give thickness to the mill spec, not a round number.
- State the bend radius if your design needs one.
- State the surface finish if the part is visible.
Two notes save the most money. Grade stated: we buy the right sheet the first time. Finish stated: you do not argue with the coating later. “Steel” and “nice finish” are the two vaguest lines in a drawing.
Five Mistakes We See Most
- Units missing: millimeters or inches, never both.
- Bend lines without radius or direction.
- No datum for the critical dimensions.
- Text notes that contradict the dimensions.
- A version number that changed without notice.
Each mistake costs one round trip. The fix is one line in your template. Our free check catches all five before any price is given. It is the first step of the full-process metal fabrication service, and it takes a day or two.
What Happens When We Receive It
- Day 0: file check against the seven lines.
- Day 1: a short question list, or the quote if clean.
- Day 1-2: DFM notes where a change saves money.
- Your call: accept the notes, or hold the design.
A clean file gets a quote inside one working day. The quote carries the sheet metal cost split: material, operations, finish. No line in the quote appears without a reason on the drawing. If it does, you will hear about it before you pay it.
Only a Photo or a Sketch?
Send it anyway. A photo gets a feasibility answer in hours. We list what the drawing will need, in the same order as the seven lines. Most clients redraw one page and come back with a real file. The 72-hour sample program then does the rest, on qualifying parts. A photo is not a metal part drawing, but it starts the clock. The obstacle is waiting for a perfect file that never arrives.
Frequently Asked Questions
What is the best file for a metal part drawing?
STEP for 3D parts, DXF for flat parts. A fully dimensioned PDF works for simple pieces.
Do I need GD&T on the drawing?
Not for most sheet metal. A general tolerance plus marked critical dimensions is enough. We will say if a feature needs more.
Can you work from a photo?
Yes, for a feasibility answer. We list the missing lines in writing. You redraw one page and send the real file.
How fast is the quote after a clean file?
Inside one working day for a single part. Assemblies and multi-part jobs take longer, stated up front.
What if my CAD shop only exports PDFs?
Send the PDF. If it carries every dimension and the material, it is enough. If not, we list the gap in one reply.
Send the Drawing, Get the Split
Send your drawing — a checked quote in one day.
WhatsApp: +86 131 1007 5546 | Email: claire@hbweizhi.cn
Or contact us online.