From: "Russell Jocoy" 
To: bobmay{at}nethere.com, atm{at}shore.net
Reply-To: "Russell Jocoy" 






>From: "Bob May" 
>Reply-To: "Bob May" 
>To: "atmlist" 
>Subject: Re: ATM tool for pitch lap...
>Date: Fri, 7 Mar 2003 10:49:35 -0800
>
>I've not found a problem with the strength of the dental stone (aka lab
>stone) in grinding and polishing of mirrors.  I'll also note that I usually
>have the guy start grinding with the 80 grit about 1/2 hour after I start
>the mixing of the plaster to the water.  At that point, the tool is hard
>enough to withstand the forces of grinding without problems.  Over the next
>hour or so, it gets a lot harder which is extra hardness that is always
>encouraged to insure the life fo the tool.
>While the largest tool that I have made is a 12.5" one, the pouring of the
>tool really wasn't that much of a problem in getting that much plaster
>mixed
>and poured in time.
>Lastly, I'd be careful of putting screen or other stuff in the tool as this
>may cause problems with stress in something that really shouldn't be
>stressed.  Others have mentioned curvature changes and other dimensional
>changes with the stuff over moisture changes as well as the well expected
>temperature changes and having a steel mesh inside forcing the stuff to
>some
>other length will cause curvature changes which will make for a lot of
>problems when finish grinding!
>The stone is quite hard and really doesn't need to be reinforced to work
>well.
>Bob May
>http://nav.to/bobmay
>bobmay{at}nethere.com
>NEW! http://bobmay.astronomy.net
>
>
>
("atm{at}shore.net")

   Bob,  I agree dental stone is some really hard stuff. Harder than any
cement based mixture that I
have worked with. There is no wonder why they have the name
"stone" in it's description. When I
first priced this product I felt it was over priced, but after using it I
was amazed......
                                      RUSS JOCOY
("atm{at}shore.net")

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