CORRECTING AN OVERCORRECT

PFAFF2@delphi.com
Wed, 08 Mar 1995 22:39:15 -0500 (EST)

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> Date: Tue, 07 Mar 1995 20:13:28 -0600
> From: Mike Abercrombie <abercrom@southwind.net>
> Subject: CORRECTING AN OVERCORRECT
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> DD> 2. Can I correct the mirror without the original tool? I
> DD> have never made a mirror but have read a lot about it. I'm
> DD> handy with my hands and do a lot of wood and metal working.
> DD> I have a home shop where I could do it. How do I make a tool
> DD> to do this? Is it worth it?
> Dean,
> Yes, you can easily make a tool to refigure the mirror. We (the
> group I grind with) make all of our tools. While you really
> don't need the full explanation for making a tool to grind with
> in order to refigure, I'll explain the construction of one
> anyway.
>
> First, locate a ceramics supply wholesale store and buy from them
> a quantity of industrial strength waterproof plaster. They use
> this as molds for firing greenware or something like that. I
> picked up a 100 lb bag of this stuff a couple of years ago for
> $12.00.
>
> Make a collar for your mirror just like you would make for the
> tool when pouring pitch for a lap. In this case though, you will
> want the collar to be at least 1.5 to 2" above the surface of the
> mirror.
>
> Place the mirror face up on a level surface and place the collar
> around it. Use a very small quantity of dishwashing liquid as a
> release agent on the mirror and the inside of the collar. Mix
> the plaster to the consistancy of pancake syrup and pour it in
> the mold.
>
> Pour it slow to avoid creating bubbles, but other than that, you
> are finished...or will be after it sets overnight.
>
> You then can pour your pitch lap and treat the tool as if it were
> pyrex.
>
> We go a step further when making these tools for grinding. We
> use ceramic floor tiles (either 1" or 2" work fine). Willman
> Bell sells hexagonal tiles for the same purpose, but I haven't
> seen that the fancy shape of W.B.'s really makes any difference
> when compared to the results of the square ones.
>
> There are two ways of "mounting" the tiles and both work well.
> The easiest is to just lay the tiles directly on the surface of
> the glass that will become the mirror and pour the plaster over
> them. You have to be careful with this though to insure that the
> tiles do not get moved out of position (they should be separated
> by a space around a quarter inch on all sides.) These tiles form
> the grinding surface.
>
> The other method, and the one I prefer, requires pouring the
> plaster first and letting it cure. Once it has completely cured,
> Epoxy the tiles directly to its surface. Again, separate the
> tiles so as to form 1/4" channels.
>
> With the embedded tile-tool, use it just as if it were a glass
> tool.
>
> With the channeled tool, the procedure is a bit different.
> Charge the heck out of the tool...filling the channels with the
> heavier grits! Your grinding will go far faster than with the
> more conventional tools because you don't have to continually
> clean and charge them. Granted, you will probably wear out
> before the charge is exhausted, but you will be able to go for 10
> or 20 minutes before having to recharge.
>
> The finer grits are no different than with a normal tool.
>
> Hope this gives you some ideas.
>
> Mike
>
> * RM 1.3 * Eval Day 6 * Diplomacy: Saying "Nice doggie" until you can
>find a r
> ock
>
>
>
>
>
Just a tip on making tile tools. I cover the mirror with about a 1/16" of thick grease such as Luber Plate. The tile are pressed into the grease on the mirror. The grease should just be thick enough to just squeez up between and to top of each tile. Do not get grease on top of the tiles. Now make a collar dam around the mirror and pour your cement ( I use Ultra Cal ). After the cement or plaster has set remove the tool and wash the grease between the tiles and you are ready. If you have a tile that does not stick just epoxy in on. Bob Pfaff