Is STEP or IGES better for CNC machining?

STEP is generally better because it transfers clean solid geometry that most CAM systems read reliably. IGES still works but can transfer surfaces that occasionally need repair.

Do I still need a 2D drawing if I send a 3D model?

For critical parts, yes. The 3D model defines the shape, but a 2D drawing communicates tolerances, threads, finishes and which features are most important.

STEP vs IGES vs 2D Drawings: What to Send for a CNC Quote

One of the most common reasons a machining quote gets delayed is a missing or unusable file. Sending the right CAD format the first time speeds up your quote and reduces the risk of errors. Here is what each format does and what to include in your request.

Why file format matters

Your machinist needs an accurate 3D definition of your part to program the machine and calculate cost. Different CAD systems save in different native formats, so neutral exchange formats exist to move geometry reliably between them. Choosing a widely supported format avoids translation errors.

STEP (.step, .stp)

STEP is the modern standard for exchanging 3D solid models and is the format most machine shops prefer. It transfers clean, watertight solid geometry that virtually every CAM system can read. If you send only one file, make it a STEP file.

IGES (.igs, .iges)

IGES is an older neutral format. It is still widely accepted, but because it often transfers surfaces rather than a single solid, it can occasionally arrive with small gaps that need repair. It remains a good backup when STEP is not available.

Native and Parasolid files

Native files (from SolidWorks, Fusion, Inventor and similar) or Parasolid (.x_t) files can also work well if your supplier uses compatible software. When in doubt, export a STEP alongside your native file so the shop has a universal fallback.

Don't forget the 2D drawing

A 3D model defines shape, but a 2D drawing communicates intent — critical dimensions, tolerances, threads, surface finish and any geometric dimensioning and tolerancing (GD&T). For anything fit- or function-critical, include a dimensioned PDF drawing so the shop knows which features matter most.

What to include with your RFQ

A 3D model (STEP preferred; IGES or native as backup)
A 2D drawing (PDF) with critical dimensions and tolerances
Material and finish requirements
Quantity and any target delivery date
Notes on the most important features or fits

Summary

For most CNC quotes, a STEP file plus a dimensioned PDF drawing is the ideal combination: the model defines the geometry, and the drawing defines what has to be right. Send us your files and we will get back to you with a quote.