Turning Operations 101

August 7, 2014

Just like milling, turning is another material removal process utilised to create rotational parts. The process is so called because of the high precision, turning-removal process made possible with highly efficient turning equipment like CNC turning machines.

In the machining process, turning is generally employed to produce rotational parts that are generally axi-symmetric and that include several features like diameter steps, contoured surfaces, grooves, tapers, threads and holes. Custom designed fasteners and shafts are typically made using turning processes that are relevant to prototypes. Also, due to better surface finishes and the high tolerance capabilities of turning processes, they are employed as a secondary process for work-piece refinements, such as adding precision rotational features.

Different Turning Operations

Where milling has four major types of operations, turning has two major classifications of operations:

External Operations are so called because the turning processes are performed on the external or outside surface of the work-piece. External turning operations are subdivided into:

Turning – a general external turning operation that uses a single-point turning tool, moving axially on the sides of the work-piece. The end product can display different features like contours, tapers, steps or chamfers.

Facing – another external operation that uses a single-point turning tool that moves radially along the end of the work-piece. This provides a smooth flat surface, in a single pass, on the turning machine or after multiple passes, using a smaller axial-cut depth.

Grooving – as the name implies, is a turning process that uses a radial turning tool to work the sides of the work-piece to cut a groove, according to the size of the cutting tool. Sometimes, a small cutting tool is able to make larger grooves by making multiple cuts on the sides of the work-piece. Special form cutting tools can also be used to create grooves with various geometric patterns.

Cut off or Part Turning – is somewhat like grooving. However, the process also parts or cuts off a section of the work-piece.

Thread Cutting – typically uses a pointed nose with a 60 degree angle, moving axially on the side of the work-piece to cut threads found in screws. Thread formation usually requires multiple passes to come up with the specified pitch and length.

Internal Operations are turning operations performed through the surface. Here are the different internal turning operations that you can perform with a CNC turning machine:

Drilling – the process by which a drill is axially inserted to a cut a hole equal to the diameter of the drill cutting tool.

Boring – is like drilling but using a boring tool instead. The boring tool can be a single-point cutting tool or it can be made up of adjustable boring heads to create different part features like tapers, chamfers, steps and contours. Usually, a drilling process is first required before a work-piece can be bored to achieve maximum dimension precision.

Reaming – is a process that enlarges an existing hole, depending on the diameter of the turning tool. This type of internal turning operation is performed to achieve a smoother interior finish and more accurate diameters.

Tapping – uses a tap which is a machining tool used to cut the female portion of a mating gear. A nut, for example, is axially inserted into the work-piece to cut interior threads into the already existing hole. The drilled hole is generally sized according to the tap diameter for easier accommodation.

Now that you know the basics of turning operations, it will be easier for you distinguish the turning operation you need to use for your design project. Make your task easier with the use of CNC turning machines.

Please contact us at CNC Turning UK if you have enquiries or if you simply want to discuss the best way to make your design project with the use of different CNC machines.