To: atmpob{at}yahoo.com
Cc: atm-digest{at}shore.net
From: martin.cibulski{at}degussa.com
Reply-To: martin.cibulski{at}degussa.com


>From: "Dale Eason" 
>
>I read with interest about putting washers on a plater tool.  Then about
using
dumps (center of the washer), and finally using nickels.  The reports said that
grinding went much faster and used less amounts of grit but to hog you needed a
tool of the proper ROC.
>
>This is what I'm planning.  A friend has a 16" F5 waiting to be polished.
I
will use that to make a subdiameter tool 12.5" out of hydrostone.  I will cover
it in nickels and use that for the hogging and fine grinding.  I'm not sure how
to attach the nickels.  They seem a little thin to just pour the plaster around
and expect them to stay put especially after digging channels around them. So I
may just epoxy them onto the surface.
>
>Has anyone experience with this? Does anyone want to comment?
>Dale Eason
>
>

Dale,

I used washers on a concrete tool for fine grinding of my 14" F5
mirror. Hogging has been done before with a iron plate mounted under a
round plywood disk (to fit into my grinding machine).

(Actually after hogging I used a tile tool with was broken during the 220
grit stage. Then I casted the washer tool from the mostly spherical mirror
and later all washers had contact)

I heated the tool in the oven (slowly increasing to >100 øC to remove any water).
Then I painted epoxy glue on the surface about 1 mm thick and put the
washers on it. From the heat the glue became fluid so the washers could
sink into the glue down to the concrete surface. The washers were embedded
in the glue, holes and gaps between them were perfectly filled.
There is not very much time to put all washers on the tool because from the
heat the glue hardens faster (less than 30min instead of 12 hours), but
finally it becomes stronger.


I wonder if it is possible to use a spherical washer tool for hogging
because the middle of the tool wears much more than the edge. So its
spherical curve will be destroyed and it might take a long time to adapt it
again to the mirror's surface ? Any comments ?


Martin

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