Machining

Q How do I prevent staining of leaded brass components which is produced after machining?

A After machining clean the components with hot detergent, rinse thoroughly in cold water then immerse in a tarnish inhibitor (a mixture of monoethylene glycol and benzotriazole) then dry in air.

Q I have some brass components which have stained on machining. How can I clean them?

A Use an acidic dip such as a mixture of citric and phosphoric acids. This is quite gentle and with care easy to use.

Q What alternatives are there to the leaded free-machining brasses such as CW614N (CZ121)?

A Brasses have been developed where the lead is replaced by silicon. These are marketed under names such as Envirobrass and Eco Brass. They are slightly more expensive than the leaded brasses and not quite as machinable, but have excellent mechanical properties.

Q We are manufacturing models of ships' propellers for testing purposes. These small scale propellers are tested to give an indication of how full size propellers will behave in water. The model is complex in shape and accuracy of 0.05mm is required. We have decided that the only economical way to make the shape is by machining, starting with a 10 inch brass billet. What type of brass would you recommend and will heat treatment be necessary?

A A leaded free-machining brass would be the best solution - CW614N (CZ121Pb3), this has the best machinability of any material. A stress relief heat treatment, just prior to final machining in a temperature range of 250 to 350^oC , would be advisable to avoid distortion.