Machine shops most commonly accept a STEP file (.step or .stp) for 3D geometry and a PDF drawing for dimensions, tolerances, and notes. Sending both is the standard practice, because the model defines shape and the drawing defines requirements.
Engineers ask what file types machine shops accept because CAD systems export many formats and not all of them transfer cleanly. This page explains which formats work, which cause problems, and what to send for a quicker quote.
What file types do machine shops accept? The common formats
| Format | Extension | Type | Notes for machining |
|---|---|---|---|
| STEP | .step, .stp | 3D solid | Neutral standard (ISO 10303). Opens in nearly every CAM system. |
| PDF drawing | 2D drawing | Carries tolerances, GD&T, finish, material, and notes. | |
| IGES | .igs, .iges | Surfaces | Older format. Often imports as surfaces rather than solids. |
| Parasolid | .x_t, .x_b | 3D solid | Clean solids, common in several CAD platforms. |
| Native CAD | .sldprt, .ipt, .prt | 3D solid | Requires the same software and often the same version. |
| DXF / DWG | .dxf, .dwg | 2D geometry | Useful for profiles, not for 3D parts. |
| STL | .stl | Mesh | Built for 3D printing. Faceted and poorly suited to machining. |
Why STEP plus PDF is the standard
A STEP file gives the CAM programmer exact geometry to build toolpaths and gives the estimator a basis for cycle time. It does not reliably carry tolerances, surface finish callouts, thread specifications, or material. The PDF drawing does. When the two disagree, most purchase orders and shop practices treat the drawing as the controlling document, so it must be current.
What Wexmar accepts
Our instant quote tool accepts PDF drawings and STEP models. Upload either, and the AI estimator returns a preliminary range. For emailed RFQs, STEP and PDF are preferred. If you only have another format, contact us before converting, because a poor conversion can lose geometry.
Common file problems and how to avoid them
- Units mismatch. A part modeled in millimeters and read as inches arrives at the wrong scale. State units on the drawing.
- Assembly instead of part. Export the single part you need quoted, or clearly label parts within an assembly.
- Cosmetic threads. Modeled threads usually export as plain holes. Call out thread size and class on the drawing.
- Revision mismatch. The model and drawing should share the same revision letter.
- Mesh exports. STL and OBJ files are triangulated and do not represent true arcs or cylinders.
Do you need a drawing if you have a model?
For simple parts with general tolerances, some shops will quote and machine from a model with a note stating the tolerance block. For anything with fits, bearing bores, threads, GD&T, or surface finish requirements, a drawing is needed. It protects both parties by recording exactly what was ordered. Parts inspected on our CMMs are measured against the drawing, as described on our inspection and quality page.
Do you need a model if you have a drawing?
No. A fully dimensioned drawing is sufficient to quote and machine. A model speeds up programming, especially for contoured or complex prismatic parts, and may reduce the programming charge. For legacy parts that exist only as paper drawings, a scanned PDF works as long as dimensions are legible.
Protecting your drawings
Drawings and models often contain proprietary design information. Ask any shop how files are stored and who can access them. If your company requires a nondisclosure agreement before releasing drawings, send it with the RFQ so review is not delayed. Mark drawings with your company's proprietary notice as your policy requires, and send only the parts you need quoted rather than a full assembly model when possible.
File checklist before you send an RFQ
- STEP file of each part, exported as a solid
- PDF drawing, same revision as the model
- Units stated on the drawing
- Threads called out by size and class
- Material, finish, and quantity listed on the drawing or RFQ
- File names that include part number and revision
For more guidance on preparing drawings, see our engineering guides.
Getting a quote
Once your files are ready, upload a drawing for an instant estimate. Upload a PDF or STEP file, review the preliminary range, and a Wexmar estimator will confirm the price. For other formats or large packages, call (315) 400-2654 or email ron@backwell.com.