Material Selection in Machining: Stainless, Alloy Steel, Aluminium and Titanium

How a part behaves in use depends not only on machining quality but on the material chosen and the heat treatment applied. Each material also calls for a different tool, cutting speed and inspection approach in machining.

Stainless steels

Stainless steel is chosen for medical parts and wherever corrosion resistance matters most. It behaves more gummy in machining and wears tools faster, so correct tool selection and coolant are important.

Alloy steels

Load-bearing shafts, gears and bushings in automotive and machinery applications usually use alloy steels that can be hardened by heat treatment. Machining is often done before heat treatment, with final size reached by grinding afterwards.

Aluminium alloys

Aluminium alloys are used for housings, brackets and covers where weight matters. They machine easily, but vibration and clamping distortion must be controlled on thin-walled parts.

Titanium

Titanium stands out in medical applications where low weight and strength are needed together. It conducts heat poorly, so heat builds up at the cutting zone; low cutting speeds and plenty of coolant are required.

Coatings and surface treatments

Processes such as anodising, nickel plating and passivation can add a few microns to a part's dimensions. Coating allowance should therefore be defined from the start, on the drawing and in the machining plan.