Granodiorite balls

["Simon Brown" <moonsong@zzzzzzzzzzzzzzz>]

Thanks, all, for your interest and kind comments. Publishing these photos
highlights the glaring weaknesses in the technique, caused mostly from being
too busy to take properly posed photos at crucial moments.

In the past, the project has created some interest around the campus, and
people often call in to check out my students' balls.

The exercise satisfies requirements in a few of the Stonemasonry
qualification standards such as templating & hand-working as well as
machining, profiling & finishing hard and soft stone. The students research
stone balls made in Europe, and calculate volume, mass and surface area of
different sizes of balls. They also record the length of time taken to make
their ball, and calculate a selling price - about $2000 - $3000 for 40 - 60
hours of hand work. When they are finished, I show them some Chinese
examples in a product brochure available for $100. Then they have to figure
how the Chinese balls can be made so cheaply!

The students are always so pleased to finish their balls - it is like
clearing an initiation bar into higher skill levels, and employers comment
on their changed attitude when they get back to work. They really do need
balls to get through this one!

The bases are made using blocks of sandstone, cut by a CNC diamond saw
mounted above a turntable. A vertical cylinder is cut by advancing the saw
blade through the stone as it turns horizontally. Then the blade is tilted
90 degrees and horizontal points are mapped and cut as rings in a 50mm high
circular profile. Then, the surface of the stone is pared smooth with hand
tools, and rubbed with carborundum stone to a fine finish. The whole process
is achieved through careful planning, using drawings and accurate templates.

Simon