From: "Dwight K. Elvey" 
To: atm{at}shore.net
Reply-To: "Dwight K. Elvey" 



>From: "Bob May" 
>
>thni chips at the edge are of no real problem other than your vanity.
>I will note that if you don't have any bevel on the edge of the mirror,
>those chips do happen.  The bevel should be at 45 degrees also as anything
>much steeper will just spall off larger chips.
>Do try to keep the tool from rocking on the edge of the glass so the
>superhigh pressures that make that spalling of the glass doesn't happen.
>Bob May
>http://nav.to/bobmay
>bobmay{at}nethere.com
>NEW! http://bobmay.astronomy.net
>

Hi
 One other issue is how one places and removes the tool.
This isn't as important at rough grinding but fine grinding can cause
chipping. Always remove the tool such that the tool touches the center of
the glass last. The same goes for placing the tool onto the glass. Place
the edge of the tool to the glass, away from the edge, first. It takes a
little practice and rough grinding is the place to start. When tool on top,
slide the tool part way off and then lift the edge of the tool to break the
two apart. When mirror on top, slide the mirror off to the side and press
down on the mirror to break the two apart.
 If you chip the tool, simply wipe the chunks of the mirror
and continue grinding. Don't try to carefully place the tool exactly evenly
on the mirror. In about one in five cases, at the class I monitor, someone
will chip a mirror with this method. Just remember tool's edge, first and
last.
 Although, I highly recommend keeping a good bevel all the
way through grinding, I've seen unbeveled mirrors go through fine grinding
without chipping when care was taken on placing and removing the tool.
Dwight

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