What is CNC turning?
The workpiece rotates while a cutting tool removes material. Turning suits many rotational parts, including shafts, bushes, spacers and flanges. Cross holes, flats and other non-axisymmetric features may need live tooling or additional operations. Specify the finished part, not only the starting diameter.
- Shafts: identify seats, shoulders and assembly surfaces.
- Bushes: define the relationship between bore, outside diameter and length.
- Flanges: specify location, mounting face and hole pattern.
Diameters, fits and datums
Parts with the same nominal diameters can require different inspections. Define datum surfaces and the geometric relationships needed for function. A fit designation does not by itself define every form, orientation or position requirement. Agree how important features will be verified.
- Relate critical dimensions to sliding, location, support or torque transmission.
- Identify datums for geometric requirements where needed.
- Request inspection of key characteristics and a report when required.
Threads, grooves and slender parts
Threads need a complete designation and useful engagement length. Dimension grooves so tools can be selected and parts inspected. On long or thin parts, workholding and support affect the process: mass and maximum diameter alone do not describe the difficulty.
- State thread type, pitch, class and useful length.
- Distinguish blind and through holes and specify functional depths.
- Flag surfaces sensitive to clamping marks and define deburring.
How to compare CNC turning quotes
Compare the same revision, quantity and specifications. Check treatments, documentation, inspection, packing and transport. Identify off-machine operations such as grinding separately. A unit price alone cannot show whether two offers cover the same supply.
- Use consistent STEP and PDF files with a part number and revision.
- Specify material, treatment and any required certificates.
- State batch quantity, required delivery and supply conditions.
This resource is informational. Requirements, feasibility and the inspection plan must be checked against the drawing and agreed for the supply.
Technical reference: Protolabs ↗