Re: ATM - Orthodontic plaster stength

["Bob May" <bobmay@nethere.com>]

Yep, that is the same stuff that I've been using.  Plaster does have a fair
bit of strength but you have to remember that it is a bit more brittle than
glass is although the dental versions of the stuff are stronger.  It can be
drilled and tapped although I have never personally found the need to do so
and I would use the Witworth spec tap system if I did such as those threads
are coarser and larger than the SAE specs and I'd probably find that the
metric system to be inadequate to the needs of the stuff.   When the stuff
does give way, it tends to merely mush on corner dings and shatter with
larger impacts that stress the stuff in a more generic way (hammer the
middle of a tool and it will break into several pieces).
Also remember that concrete is another of the family of chemicals that take
up water and change thier chemical constitution and that stuff is used
everywhere for construction purposes.