Turning, Milling or 5-Axis Milling? The Processes Compared
Which CNC process suits which component, with a comparison table
The rule of thumb: round, rotationally symmetrical parts are turned, while prismatic parts with flat surfaces, pockets and hole patterns are milled. Complex parts with inclined surfaces on several sides are a case for 5-axis milling, large and heavy parts for the boring mill, and the highest accuracy is achieved by grinding.
This guide from MWA – Mechanische Werkstätten Anhalt GmbH in Halberstadt compares the processes. Many parts need several of them, which is why we offer milling, turning, drilling and grinding from a single source.
Guide: Which Process for Which Part?
The processes at a glance: click on a topic to expand it. This guide is a general orientation; we make the choice for your part together, based on the drawing.
What is the basic difference between turning and milling?
In turning, the workpiece rotates and a stationary tool removes material. This produces round shapes such as cylinders, cones, threads and grooves. In milling, the tool rotates and moves relative to the workpiece. This produces flat surfaces, pockets, slots, contours and hole patterns.
Modern machines blur the boundary: turn-mill centres can turn and mill on one machine. What remains decisive is which shape makes up the largest part of the component.
The processes compared: table
| Process | Typical parts | Strength | Limit |
|---|---|---|---|
| Turning | shafts, pins, flanges, bushings, rings | round shapes quickly and with round accuracy | only rotationally symmetrical shapes without additional machining |
| 3-axis milling | plates, housings, brackets, bars | flat surfaces, pockets, slots and hole patterns | each additional side needs a new setup |
| 5-axis milling | multi-sided parts, inclined holes, free-form surfaces | many sides in one setup | more complex programming |
| Boring mill machining | large housings, machine beds, frames | large and heavy parts, long precise bores | usually not economical for small parts |
| Grinding | bearing seats, fitting surfaces, hardened parts | very tight tolerances and fine surfaces | low material removal, usually only final machining |
The table shows typical cases. Many components combine several processes, for example a turned shaft with a milled keyway and a ground bearing seat.
When is turning the right choice?
Whenever the part is round at its core: shafts, pins, axles, flanges, bushings, discs and rings. Turning produces diameters, face surfaces, cones, threads, grooves and relief grooves in one setup with good concentricity.
More on the page Turning and grinding.
When is milling the right choice?
When the part is prismatic, that is, made up of flat surfaces, edges, pockets and holes: plates, housings, brackets, holders, bars and fixture parts. On a 3-axis machining centre, the sides are machined one after another, with one setup per side.
More on the page CNC milling.
When is 5-axis milling worthwhile?
When a part has surfaces, holes or contours on several sides and at inclined angles. The machine tilts the workpiece or the tool, so that many sides are produced in one setup. This saves reclamping and keeps the position of the features relative to each other accurate.
A distinction is made between positional machining, often called 3+2, in which the machine tilts into a fixed inclined position and then mills with three axes, and simultaneous machining, in which all five axes move at the same time, for example for free-form surfaces. More on the page 5-axis milling.
What can a boring mill do?
A boring mill is a large horizontal machine for heavy and bulky workpieces. It mills and drills large surfaces and produces long, precisely aligned bores, for example in gearbox housings, machine beds and frames. A rotary table allows several sides to be machined.
More on the pages Boring mill machining and Large-part machining.
When is grinding used?
Grinding is used when turning or milling cannot economically achieve the required dimensional accuracy or surface, for example on bearing seats, fitting surfaces and sealing surfaces, or when a part has to be finished after hardening. Grinding removes only little material and is therefore usually the last operation.
More on the page Turning and grinding.
What if my part needs several processes?
That is the normal case. What matters is that the operations are well coordinated and the part is not needlessly shipped between companies. MWA mills, turns, drills and grinds from a single source, for small to medium-sized parts up to Ø 2,500 mm, 6,000 mm in length, 3,000 mm in height and 25 t, from prototype to series.
You do not have to specify the process yourself: send us your drawing via the page Contact, we check the feasibility free of charge and propose the manufacturing route. An overview of all services can be found on the page Contract manufacturing.
Which process suits your part? Ask us.
Send us your drawing (PDF, STEP, DXF, DWG or IGES) with material, quantity and desired delivery date. We check feasibility free of charge and get back to you with a quote within 24 hours on working days.