Re: [ATM] mirror grinding

["David Harbour" <scarab2@cox.net>]

No, I am not that bright, thank you Gary.

You and your family are dear to me. Especially Rachel. Send her up here.

Dave


----- Original Message ----- 
From: "Gary Fuchs" <gary@rcn.com>
To: "David Harbour" <scarab2@cox.net>
Sent: Tuesday, June 28, 2005 6:23 PM
Subject: Re: [ATM] mirror grinding


> Hi Dave,
>
> Not to speak for anyone, but I believe the "hole" referred to is the
> sagitta. You knew that, right...
>
> Gary
>
>
>
>
>
> David Harbour wrote:
>
> >Bob,
> >
> >I am ashamed to say that I haven't a clear notion of this thread. I went
> >back and checked the previous posts, and am embarassed to tell you that I
do
> >not understand a coule of things; I'll bet you can explain them with an
> >economy of words. When I was essentially teaching myself how to use tile
> >tools ("channeled" tools) for my first mirror that I was going to use
(12.5"
> >f/8 for Moon and planets) I made a flat tool to start with, using Winburn
1"
> >hex tiles; I would have used the 2" tiles, except I knew I would have to
> >re-tile at some point (I did: the edge tiles got MIGHTY thin) and I knew
> >that the one inch tiles would come to curve quicker.
> >
> >Now, I did re-tile, with epoxy and one inch Winburn hexes; I used two
tube
> >clear epoxy resin and hardener. Here is my question: what would have been
> >the matter with me just epoxying on TWO LAYERS OF TILES to begin with;
same
> >number of tiles, same (actually, a little less) labor; i.e., you
mentioned
> >economy. Same number of tiles, same amount of labor. My substrate was a
four
> >layer sandwich of Terra Cotta glazed 12" floor tiles (usually they will
give
> >you four or five for free, "samples", to help you decide what kind of
> >kitchen or bathroom tiles you will want at the tile company). I had a
> >lapidarist zip them nearly round in a few minutes (using dangerous PVC as
a
> >lubricant for his cutting wheel; I'll probably croak of PVC poisoning-
> >probably what's the matter with my head now!).
> >
> >Now, I am embarassed to admit this to you (even after reading previous
posts
> >to this thread: what is this "hole" you are talking about? My tools never
> >had a "hole" in them; even my largest. What is this hole you are
referring
> >to? What is its form and what is its function? My laargest tool was a
> >Porland cement/Winburn Hex tool; worked like a dream. Wish I still had it
as
> >a souvenir. Got away from me, like everything does.
> >
> >http://www.atmsite.org/contrib/Harbour/Tool.html  (This article is for
> >making tools for curve generated mirrors only- many basics apply for a
flat
> >one, though. I have an article for a flat one on my machine.
> >
> >I never used a new substrate; I just re-tiled with two tube epoxy cement.
> >What I really wanted to do was to have the cojones to try my radical plan
of
> >a tile tool made this way: six or seven Terra Cotta (with Terra Cotta
floor
> >tiles  ground flat first of with 40 grit) epoxied together for substrate,
> >and then pave the grinding face, waxed and excavated as per correct
> >practice, with three or four layers of two inch diameter Winburn Hexes
> >"stacked" for the grinding face. I hope I have posed my questions clearly
> >enough for you, Bob, BECAUSE I KNOW THAT Y0U HAVE THE RIGHT ANSWERS: YOU
> >ALWAYS DO. Just don't understand the hole thing, or why anyone has to use
> >more than one piece of glass (or any piece of glass) for the substrate
tool,
> >when you can get these 12 and 13 inch Terra Cotta floor tiles. Straighten
me
> >out, Master.
> >
> >I don't know how many have ever used three or four 12.5" Terra Cotta tile
> >tools as a substrate- pretty neat- nearly as dimensionally stable as
glass,
> >and usually- FREE.
> >
> >Dave
> >
> >P.S. tell me about this hole, Bob.
> >
> >
> >----- Original Message ----- 
> >From: "Bob May" <bobmay@nethere.com>
> >To: <atm@atmlist.net>
> >Sent: Tuesday, June 28, 2005 1:13 PM
> >Subject: Re: [ATM] mirror grinding
> >
> >
> >
> >
> >>----- Original Message -----
> >>From: David Harbour <scarab2@cox.net>
> >>To: ATM List <atm@atmlist.net>; Bob May <bobmay@nethere.com>
> >>Sent: Tuesday, June 28, 2005 6:15 AM
> >>Subject: Re: [ATM] mirror grinding
> >>
> >>
> >>
> >>
> >>>Bob-
> >>>
> >>>I have often thought about this: why couldn't a guy, who knew he was
> >>>
> >>>
> >going
> >
> >
> >>>to do a deep (fast) large mirror, start with a flat tiled, channeled
> >>>
> >>>
> >tool,
> >
> >
> >>>with say, three or four layers of tiles epoxied on at first! THEN HE
> >>>WOULDN'T HAVE TO RE-TILE!!!! HAS ANYONE EVER THOUGHT OF THAT?
> >>>Dave in Oklahoma (oops! "Okrahoma")
> >>>
> >>>Thanks, Bob-
> >>>Dave
> >>>
> >>>
> >>>
> >>Cost!  Why spend money when you don't have to!  The idea behind tile
tools
> >>is to drop the cost of making a mirror by replacing the expensive piece
of
> >>glass to be used as a tool with plaster and tile and a cheap piece of
> >>
> >>
> >metal
> >
> >
> >>for digging the basic hole that ends up being less than 10% of the cost
of
> >>that glass.
> >>Bob May
> >>bobmay@nethere.com
> >>http://nav.to/bobmay
> >>http://bobmay.astronomy.net
> >>
> >>
> >>_______________________________________________
> >>ATM mailing list http://www.atmlist.net/
> >>
> >>
> >>
> >
> >
> >_______________________________________________
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> >
> >
> >
>
>


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