Re: ATM beginner tool questions

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

The tile tools work just fine at a 6" diameter.  You will want to use a
smaller end cap to do the coarse grinding (you don't form the basic hole
with tile tools but rather finish up an already formed cavity made with
something else) or something else like a 2" OD or so diameter chunk of metal
in a ring shape (rings will grind a basic spherical shape without the need
to form the grinding surface to a basic radius)  and grind out the center of
the mirror.  The F8 can probably be started from the flat surface but the
sad thing is that the blanks you get from WB really aren't flat to begin
with so you don't want to start immediately with making a tool.
I like using dental stone (usually the yellow lab stone as the pink is sort
of femine althouth the blue is the same for the gals) as it allows me to
start grinding in about a half hour (working time is about 5 minutes from
the initial pouring of water into the powder!) after I start mixing the
stuff.  That means that I can quickly setup and pour a tool for somebody
without them worrying about curing of the tool for days or weeks.  Hydrocal
also works about as fast and is essentially the same material.  Hydrocal is
used a lot for outdoor staturary.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net