GlossaryKind of term: Manufacturing termTurning
What is turning?
Turning is machining in which the workpiece rotates and a non-rotating tool moves along and across it, producing diameters, faces, grooves and threads.
The part spins about its own axis, so what results is rotationally symmetric: besides outside diameters and faces, also shoulders, tapers, bores by internal turning and the parting off of the piece. The starting material is often bar, but can also be tube, a sawn slug, a forging or a casting. Features that are not rotationally symmetric about the spindle axis, such as a cross hole or a spanner flat, need live tooling, a mill-turn machine or a separate milling operation.
What decides the result in turning?
Cutting speed follows from spindle speed and diameter, vc = π × D × n / 1000 in m/min with D in mm and n in rpm: at constant spindle speed it falls towards the centre. That is why lathes often run at constant surface speed, capped at a maximum spindle speed. Size and finish depend on feed, insert corner radius, depth of cut, material, the stiffness of part and workholding, and the condition of the machine. A long, slender shaft can deflect under the cutting force and then needs support from a tailstock centre or a steady rest. Within one setup the runout between turned features depends mainly on the spindle and machine; the workholding, whether chuck, collet or soft jaws, comes into play once features from different setups, or an unmachined surface, must run true to each other.
How does turning work in practice?
On bar work, the material line per piece usually counts the part length plus parting-off width and a facing allowance, and each bar leaves an offcut; sawn slugs add a clamping length. A bar feeder or loader takes over the handling per piece, but setup time per batch remains. Tight fits or a low roughness can call for a fine finishing pass, reaming or grinding, sometimes subcontracted. For a rotationally symmetric part turning is often more efficient than milling from a block; by how much is set by the shape, the number of non-round features and the quantity.
What is turning often confused with?
Turning is not mill-turn: an ordinary lathe does the round work and a cross hole goes to another machine, while a mill-turn machine does both without a manual reclamp. Nor is conventional turning the same as Swiss-type turning, which runs on a sliding-headstock lathe with a guide bush, for long, slender parts.
How do you see turning in Blake?
In Blake, turning is calculated in separate lines for material, machining, finishing, setup and programming, per piece and per batch. The result carries the estimate label. More on turning.
Frequently asked questions
Is turning cheaper than milling for a round part?
For a rotationally symmetric part it often is: few tool changes, efficient stock removal and, on bar work, little handling per piece. The advantage shrinks as cross holes, flats or slots are added. Quantity, machine and hourly rates decide.
Can I hold a tight fit by turning alone?
Often, depending on tolerance, diameter, material, stiffness and machine. For the tightest fits or a low roughness, turning is sometimes followed by grinding or honing, in house or subcontracted, with its own time and lead time.