Turning – a machining process for metal casting

Published - 8th Nov 2016

Previously in this blog, we’ve looked broadly at the four main machining processes employed at Haworth Castings – turning, milling, surface grinding and manual drilling.

In the first of a series of blog posts, we’ll be looking in detail at each process. We start with turning.

Manual or automated turning?

Machining essentially transforms an aluminium casting into a finished component. Turning is used to add or refine internal or external features that cannot be produced during the aluminium casting process. It can be carried out manually on lathes or using computer numerical control (CNC) machines.

Manual turning requires expert skills on the part of the operator, who manually operates the lathe. It is very useful for producing one-off components.

Machining of large quantities is more typically carried out using CNC machines, which are programmed to carry out certain turning operations. This offers a more cost-effective and consistently reliable technique for medium- and high-volume requirements.

Turning using CNC machines

Using this process, a component is positioned in a chuck or turning fixture in a lathe/CNC machine. The component is then rotated at speed.

A specialised cutting tool, manufactured from ceramic or carbide material, is traversed to the work piece along various axes of movement. The tool removes any unwanted material from the inside or outside of the casting to create the desired shape, dimensions and features.

The choice of tool is determined by a number of factors, including the component material and required finished.

Turning operations

Turning is used to describe a variety of operations on both the internal and external surface of the casting. These include:

• Facing – removing a thin layer of the material to create a smooth flat surface
• Drilling – creating a hole inside the work piece. The hole is always cylindrical in shape and circular in diameter.
• Boring – enlarging a drilled hole to meet precise specifications in terms of size and surface finish
• Reaming – sizing and finishing a hole that has already been drilled or bored
• Thread cutting – cutting threads into the inner and outer surface (e.g. for nuts and bolts)
• Grooving – creating deep grooves on the external and internal surfaces to specific dimensions
• Knurling – cutting a serrated edge onto the surface (e.g. for a hand grip)

Our highly skilled technicians keep the process carefully monitored throughout – checking that there is no tool wear or that the fixture has not moved.

We use a wide variety of CNC machines at Haworth Castings to meet our customers’ differing requirements. Horizontal machines are the most commonly used but vertical ones are useful for large diameter parts.

Some machines are also capable of live tooling – which enables them to carry out both turning and milling at the same time.

In the next blog, we will take a look at milling in more detail.

Want to find out more about our machining capabilities? Call us today on +44 (0)1794 512685 or email: sales@haworthcastings.co.uk