What is the best CAD file format to send for CNC machining?

STEP (.stp or .step) is the preferred format. It is a neutral solid-geometry format that is readable by all major CAM systems, preserves the full 3D solid model, and does not require the recipient to have the same CAD software. Always send a dimensioned PDF drawing alongside the STEP file.

Can I send a SolidWorks file (.sldprt) for CNC machining?

Yes. Oyster-CNC uses SolidWorks in-house, so native .sldprt and .sldasm files are readable directly. However, STEP is still recommended as the primary format for compatibility, with the native file as a supplement if needed.

Do I need to send a drawing as well as a 3D model?

Yes. A 3D model alone is not sufficient for CNC machining. The drawing carries the tolerances, surface finish requirements, material specification, and general tolerance standard. Without a drawing, the machinist has no way to know what dimensional variation is acceptable.

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Sending CAD Files for Machining

The file you send us has a direct bearing on how quickly we can quote and programme your parts.

CNC machining requires two things from a CAD submission: an accurate 3D solid model and a fully dimensioned drawing.

File Formats

STEP (.stp / .step)

Recommended

Our preferred format.

Format Comparison at a Glance

Format	Solid geometry	Neutral format	Carries tolerances	Verdict
STEP (.stp)	✓	✓	✗	✓ First choice

Notes for SolidWorks Users

We use SolidWorks in-house, so native .sldprt and .sldasm files are readable directly.

What Your Drawing Must Include

General tolerance standard: State ISO 2768-m or ISO 2768-f in the title block.

Submission Checklist

Send a STEP file as your primary 3D model.

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