Page 21 - Curriculum Visions Dynamic Book

 The first brass was made by the Romans about two thousand years ago. They found it especially valuable for making coins. Brass was also popular
because it has an attractive colour and it is much cheaper and
stronger than pure copper. This is a brass “sanctuary”
knocker on the door of a cathedral.
 Brass is cast (as in taps), machined (as in screw threads on plumbing connectors), or punched out and then machined,
as in cylinder lock keys.
alloy: a mixture of a metal and various other elements.
corrosion: the slow decay of a substance resulting from contact with gases and liquids in the environment. The term is often applied to metals. Rust is the corrosion of iron.
The cylinder lock
The cylinder or pin-tumbler lock, often popularly called the “Yale” lock after its American inventor, is made out of brass for a number of reasons. For example, brass does not corrode readily, a major advantage when using locks fitted to street doors that are exposed to the weather.
The pins, the cylinder and all the other components can be cast and turned easily, yet they are strong enough to resist attempts to break the lock.
 Bronze is usually
made from about
78% copper and 12% tin.
Adding zinc and lead to the
bronze alloy produces a material
that is much more suitable for casting.
An alloy with about nine-tenths copper and equal proportions of the other metals is called gunmetal. It was commonly used in cannon, not only for its corrosion resistance but also for its machinability.
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