Feasability of a Big Lathe?

[Simon Brown <moonsong@zzzzzzzzzzzzzzz>]

John,

Your Dad's lathe sounds like a beauty! Can't wait to see pictures. I'll have a
go at some of your questions.

I worked with old masons who remembered using Krupp's gun lathes from WW1
Germany to turn granite columns. This was before the days of diamond blades, and
the columns were hand-worked before placing on the lathe for finishing. A good
description of this process has been published by Peggy and George Perazzo at:
http://www.cagenweb.com/quarries/
Click on Stone Carvers/Stone Cutters, Methods, How Granite Columns are Polished.

Another source of photos: Quincy Column Turning Co:
http://ci.quincy.ma.us/tcpl/htm/quarry/work2.htm

The diameter/length ratio depends on the type of stone and its integrity.
Structural bedding is also important, that is, the grain of the stone. A column
should be 'naturally bedded', grain horizontal after installation. Laying a
column sideways in a lathe and exerting a sideways shaping force will soon find
structural faults. Ideally, a column should be stood on end in a vertical lathe,
and its profile shaped with a vertically travelling diamond saw.

A tall column can be created from separate drums, anyhow. Recipes for column
proportions simplified here: http://www.e-mantels.com/history.htm

A photo of a diamond saw mounted on a lathe (the lathe doesn't have to be
spinning fast):
[URL now obsolete]

And a tantalising glimpse of some other pretty fancy stuff:
http://www.smv.org/Kugels/index1.htm
Notice that the most interesting photo doesn't display the large version (left
column, 3 down: a polishing head finishing a Kugel).

The strength of a stone will not guarantee suitability for inclusion in a a
modern building. Engineers know how steel-reinforced concrete will behave under
load, but are extremely suspicious of natural stone's properties. A large
granite column will most likely be specified as Clive has noted, cladding around
a steel & concrete core.

Maybe you could create your own market! Of course there is the question of
infrastructure, like lifting and handling gear, water recirculation, diamond
tooling. It would help if you owned a stone quarry too. Then you could name your
own price.

Safety? Just think of the opening scenes of 'Raiders of the Lost Ark' when
Harrison Ford is outrunning the papier mache ball.

Simon