To send a drawing to a machine shop, attach a PDF of the dimensioned drawing and a STEP file of the 3D model at the same revision, then add quantity, material, finish, and documentation requirements. The PDF governs tolerances and notes, and the STEP file lets the shop program the part without redrawing it.
Most quote delays come from missing information, not from the shop's workload. Sending the right files and details the first time gets you an accurate machining quote faster and reduces questions after the order is placed.
Which file formats a machine shop needs
| File | Format | Purpose |
|---|---|---|
| 2D drawing | Tolerances, GD&T, thread callouts, finish, notes, revision | |
| 3D model | STEP (.stp or .step) | Geometry for CAM programming; opens in nearly any CAD system |
| Alternate model | IGES, Parasolid (.x_t), or native CAD | Accepted by most shops if STEP is not available |
| Legacy drawing | Scanned PDF or TIFF | Usable if legible; the shop may model the part from it |
| Mesh files | STL | Not suitable for machining; faceted surfaces lack true geometry |
If you have only a model, the shop can often quote from it, but expect questions about tolerances and finish. If you have only a drawing, the shop can build a model, which may add a small programming charge.
What to include with the drawing
- Revision letter on both the drawing and the model, and confirmation that they match.
- Quantity, plus any quantity breaks you want priced.
- Material by specification and condition, for example 17-4 PH condition A, or 6061-T6.
- Finish and outside processing by specification: heat treat, plating, anodize, passivation.
- Documentation: material certs, certificate of conformance, CMM report, FAI.
- Required delivery date and ship-to location.
- Sourcing requirements such as DFARS specialty metals or Buy American.
How to prepare a drawing a machine shop can quote quickly
Make the title block tolerance realistic
A general tolerance of plus or minus 0.005 in on three-place decimals is typical for machined parts. Call tighter tolerances directly on the features that need them.
Call out threads completely
Give size, pitch, class, and depth, such as 1/4-20 UNC-2B, 0.50 deep. Our page on specifying threads on a drawing covers this in detail.
State surface finish
Give a default Ra value in the notes and call finer finishes on specific surfaces. See our explanation of surface finish Ra.
Identify critical features
If certain characteristics are key to fit or function, flag them. The shop can plan inspection around them and report them on the CMM report.
Assemblies and multiple parts
If you are quoting several parts from an assembly, send a separate drawing and model for each machined component, plus the assembly drawing for reference. Name files by part number and revision so the estimator can match them. List which parts are machined and which are purchased hardware.
Common drawing problems that delay quotes
- Model and drawing at different revisions: the shop must stop and ask which one governs.
- Material called only as steel or stainless: the grade and condition change the price and the process.
- Missing tolerances: dimensions with no tolerance and no title block default leave the shop guessing.
- Obsolete specifications: older drawings may cite cancelled plating or material specs; state the current equivalent.
- Unclear datums: GD&T controls without datums, or datums that do not match how the part functions, create inspection questions.
- Notes that conflict with callouts: for example, a general finish note that a local callout contradicts.
Fixing these before sending the RFQ saves a round of questions and keeps the quote accurate.
Protecting your drawing
If your drawing is proprietary, send it with your NDA or mark it with your proprietary notice. A direct shop receives your files and quotes them in-house, which limits how many parties see your design compared with a marketplace that routes files to multiple suppliers.
Checklist before you hit send
- PDF drawing, current revision, legible, with title block complete.
- STEP model at the same revision.
- Quantity and quantity breaks.
- Material specification and condition.
- Finish and outside processes listed by specification.
- Documentation and sourcing requirements stated.
- Delivery date and ship-to address.
Getting a quote
At Wexmar you can upload a drawing for an instant estimate as a PDF or STEP file. A human estimator then reviews the drawing, confirms the price, and sends any questions. You can also email files to ron@backwell.com or call (315) 400-2654. For process details, see our capabilities page.