Turning or Milling Metal: What the Difference Is and How to Choose

The main difference between turning and milling

In turning the workpiece is held in a chuck and rotates, while the cutting tool stays still or moves along the axis. This forms surfaces of revolution: cylinders, cones, threads, holes along the axis. More in the article metal turning services.

In milling the cutter rotates and the workpiece is clamped still on the table. This forms flat faces, slots, pockets and complex contours. More in the article metal milling services.

Turning compared with milling

The table sums up the main differences that help choose a method.

The split is approximate: many parts need both kinds of machining.

Combined turning-milling: when you need both methods

Many parts combine round and flat features: a shaft with a keyway, a flange with bolt holes and flats, a bushing with a cross hole. So turning-milling is not a separate method but a sequence or combination of the two. Each is used where it gives the required shape and accuracy.

The fewer times the part is re-clamped, the easier it is to hold concentricity and dimensions. This is worth considering in the drawing, especially when several surfaces must be exactly concentric.

We carry out turning and milling on CNC machines to the customer’s drawing. For tooling — dies, punches, matrices and rolls — we use both methods, together with heat treatment and nitriding: machining and tooling.

How to choose the kind of machining

The customer usually does not need to choose the process: the contractor does that from the drawing. It is enough to describe the part exactly:

• the shape: round section or flat faces, slots, pockets;
• the material and steel or alloy grade;
• the dimensions of the blank and of the finished part;
• the requirements for dimensional accuracy, concentricity and roughness;
• the number of parts: a one-off or a batch;
• heat treatment and coating after machining.

From such data the contractor selects the sequence of operations and calculates the cost.

What to state in a quote request

Send a drawing, and if possible a 3D model or a sketch with dimensions. Add the material, the quantity, the accuracy and roughness requirements, the heat treatment or coating needed and the date you want. For structures after machining you can order hot-dip galvanising or powder coating, and for blanks cut from sheet, laser or plasma cutting.

We price from the drawing, and the lead time depends on how complex the parts are and how busy the workshop is. If you do not know something, leave the field blank and we will clarify it when we calculate.