tungsten for granite working

["Simon Brown" <moonsong@zzzzzzzzzzzzzzz>]

Hi Tomas,

Tungsten refers to the tungsten carbide inserts in the end of some stone
working tools.

My understanding is that tungsten carbide is a combination of Tungsten (a
non-ferrous metal) and Carbon. It is formed from a powder which is pressed
into a mould in the shape of the required insert and then heated until it
becomes 'sintered' (crystallised). It is this crystallisation that makes
tungsten carbide both hard and tough, an unusual combination.

Different ways of making the tungsten carbide results in a variation in
hardness from very hard and brittle to relatively soft and shock-proof. The
hard type is used in metal lathes for finishing hard steel to a fine finish,
the softer type is used where rough steel castings are turned to a true
shape.

Tungsten carbide (or tungsten for short) tools are used widely in the stone
industry where wear resistance is important, however specialist carving in
softer stones require a sharper edge for fine detail and some finishes.
These finishes are provided by fire sharpened steel tools, maintained in a
forge. While tungsten is tough, it doesn't hold a fine edge like steel tools
do.

In the old days, large Stonemasonry workshops had a resident Blacksmith who
would regularly send his boy round the mason's shop to pick up discarded
steel tools for resharpening. Masons had to amass a large number of tools to
keep working while half of their collection was in the Blacksmith's shop.
The development and availability of tungsten carbide inserts in stone
working tools removed the Blacksmith from the stoneyard to the specialist
tool maker's workshop.

Any new tungsten tools that I buy are specified for granite use, and we use
them for both hard and soft stones. We do use firesharps, and we show the
apprentices how to make and maintain them, but as soon as you look away,
someone is thrashing them on a hard stone! Firesharps are great if you can
keep them for their proper use.

Simon