Goldsmith
A goldsmith might have a wide array of skills and knowledge at their disposal. Gold, being the most malleable metal of all, offers unique opportunities for the worker. In today's world a wide variety of other metals, especially platinum alloys, also may be used frequently. 24 karat is pure gold and historically, was known as fine gold.
Machinability
Aluminium is a much softer metal than steel, and the techniques to improve its machinability usually rely on making it more brittle. Alloys 2007, 2011 and 6020 have very good machinability.