Turning

Turning creates cylindrical parts by rotating the workpiece against a cutting tool, delivering accurate diameters, bores, and threads efficiently from bar or blank.

Overview

Turning is a machining process where a lathe rotates the part while a cutting tool removes material. It excels at round geometry: OD/ID diameters, shoulders, tapers, grooves, bores, and external/internal threads. It’s commonly run on 2‑axis CNC lathes, Swiss machines for small precision parts, or mill-turn platforms with live tooling for added features.

Choose turning when the part is primarily axisymmetric and you want good concentricity and surface finish with fast cycle times. Bar-fed turning is efficient for small-to-medium parts and repeat runs; chucking works for larger diameters or forgings/castings.

Tradeoffs: non-round features often require secondary ops (milling/live tooling), and long slender parts can deflect without support. Internal features are limited by boring bar reach and stiffness. Tooling setup and workholding drive cost on low quantities; volumes typically benefit from dedicated setups or multi-spindle equipment.

Common Materials

  • Aluminum 6061
  • Stainless 303
  • Stainless 304
  • Steel 4140
  • Brass C360
  • PEEK

Tolerances

±0.001"

Applications

  • Shafts and axles
  • Threaded fastener bodies
  • Hydraulic fittings
  • Bearing spacers and sleeves
  • Valve stems
  • Instrument bushings

When to Choose Turning

Turning fits parts dominated by cylindrical geometry where diameters, bores, grooves, and threads control function. It’s a strong choice for prototypes through production, especially when bar stock can be used and features can be completed in one or two lathe setups. Expect best results when critical features share a common axis and can be machined with rigid support.

vs Milling

Choose turning when the critical geometry is round and concentricity between OD/ID features matters. Turning typically holds diameters and coaxial relationships more efficiently, especially from bar stock. Milling becomes attractive when the part is prismatic or dominated by planar pockets and complex 3D surfaces.

vs Drilling

Choose turning when you need accurate, straight, coaxial holes or bores relative to turned diameters, or when the hole transitions include steps, chamfers, grooves, or threads. A drill alone is fast for simple through-holes, but turning with boring/reaming controls size and finish better. Turning also integrates OD/ID work in the same setup to maintain alignment.

vs Grinding

Choose turning when you can meet tolerance and surface finish requirements with cutting tools at lower cost and higher material removal rates. Grinding is better for very tight size control, fine finishes, or hardened materials where turning struggles. Turning often serves as a rough/finish step before selective grinding on critical diameters.

vs Electrical Discharge Machining (EDM)

Choose turning for conductive materials when the geometry is rotational and you want faster cycle time and lower cost per part. EDM is reserved for features that are hard to cut mechanically—very hard alloys, sharp internal corners, or delicate features where cutting forces would distort the part. Turning generally delivers better throughput on standard shafts, sleeves, and threaded parts.

vs Broaching

Choose turning when the part is mostly round and you need flexible feature changes without dedicated broach tooling. Broaching can be economical for high-volume internal splines or keyways, but it depends on specialized tooling and stable volumes. Turning handles the bulk geometry and can pair with secondary ops if a broached profile is still required.

Design Considerations

  • Dimension critical features from a common datum axis and call out runout/concentricity where it matters, not on every diameter
  • Avoid long L/D slender sections without support; add center-drill features or specify steady-rest/ tailstock-friendly geometry
  • Keep internal bores realistic for tool reach; minimize deep small-diameter bores or allow reliefs for boring bar clearance
  • Use standard thread forms and provide clear thread callouts with class/fit, length of engagement, and undercut/runout requirements
  • Add chamfers or radii on edges to reduce burrs and tool breakage; specify deburr expectations explicitly
  • Specify stock form (bar, tube, casting) and any critical material condition/heat treat up front to prevent rework and quoting assumptions