Re: [ATM] mirror grinding

[Ken Hunter <atm_ken_hunter@yahoo.com>]

David...

The problem with multi-layer tiles is eventually some
of the tiles will wear down to a feather edge and that
feather edge has a nasty habit of breaking off pieces
that make imitations of the Grand Canyon on the ground
surface of your optic. This happens unless you start
off with a pre-curved mirror blank and make the layers
conform to the curve but then you really don't NEED
the multi-layers.

Ken Hunter


--- David Harbour <scarab2@cox.net> wrote:

> Peter,
> 
> I've seen this. I believe it was in one of those two
> volumes Wilman Bell
> published, the new ones, covering "recent" (last 30
> years) of amateur
> telescope making innovations. I believe I would
> rather not use Terra Cotta
> tiles for the cutting face; rather, harder tiles,
> such as the Winburn Hex,
> or the other new, square, porcelain  tiles. Winburn
> folded, went out of
> business. Besides, it's easier to make stacks of
> tiles than sideways
> sandwiches of them, I would think. How many layers
> would a guy need, anyway?
> I can't imagine more than about four or five layers
> of .2" hexes (or
> squares). I'm sure it worked for him; but was it
> necessary, I wonder? I
> wonder how much tile he had leftover? I'll bet,
> quite a bit, after grinding.
> But remember, Terra Cotta is a lot softer than
> porcelain.
> 
> Ritchey ground elegant channels into his all glass
> tools. The ultimate
> tools. Glass, with channels ground in. Ritchey was a
> perfectionist, as well
> as a genius (with a flawed personality, like yours
> truly). Thanks for
> reminding me of this-
> 
> Davey
> 
> dave
> 
> 
> ----- Original Message ----- 
> From: "Peter John Smith" <pjifl@bigpond.com>
> To: "The Amateur Telescope Makers List"
> <atm@atmlist.net>
> Sent: Tuesday, June 28, 2005 8:29 AM
> Subject: Re: [ATM] mirror grinding
> 
> 
> > Another way to make tiles last a long long time is
> to stack and glue them
> on
> > edge so they are effectively very very deep.
> >
> > This is an idea I originally saw in the McIntosh
> edited book which owed
> much to
> > the Maksutov Papers way back.  Dont remember the
> originator of the idea.
> >
> > Peter Smith
> >
> >
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
> >
> 
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 


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