Brass, bronze, copper

Brass cuts easily with short chips and holds fine dimensions - hence the classic choice for small valve and fitting parts. Bronze wants genuinely sharp edges, as it tends to smear onto the tool. Pure copper is the hardest of the three to finish: soft, and it drags under the edge. All three conduct heat well, so the part stays cool while being machined but expands noticeably in the hand - where tolerances are close, the measuring temperature belongs on the drawing.

Say which property matters: conductivity, friction behaviour or appearance. This is not a question of style - it decides the grade, and the grades in this group are not interchangeable. For bearing bushings, specify the fit and the running clearance, not just the diameter: that is where it is decided whether the part works or seizes.

Brass cuts cleanly and fast, with short chips, and takes high feeds - which is why it is the material of choice for high-volume small parts. Copper is the opposite: soft and tough, it sticks to the edge and demands sharp tools with open geometry. Bronze sits between them, but varies widely from grade to grade, so the grade is confirmed before quotation.

• Bearing bushings and guides
• Fittings and connectors
• High-volume small parts
• Electrical components
• Parts where friction matters