Re: [ATM] Material for Tool

[Jeff Lowe <lowe@nanotechsys.com>]

From: "Francis J. O'Reilly" <foreilly@verizon.net>
> Subject: Re: [ATM] Material for Tool
> To: "Dave and Connie" <dmatt@frontiernet.net>,	<atm@atmlist.net>
> Message-ID: <000a01c853ef$cfd08ea0$0100a8c0@HELENYLCMWAV95>
> Content-Type: text/plain; format=flowed; charset=iso-8859-1;
>	reply-type=original
> Dave,
> try http://plaster-supply.com for Quick Set Dental Stone. Compressive 
> strength, about 7400 psi. 20 pounds for $33.25, shipping included.
> I am about to complete a video that will be posted to You Tube showing how I 
> made a seven inch flat tool for a pitch lap.

Plaster Supply also sells on ebay and for some reason is less expensive there (22.49 for 20 LB delivered).
I tend to favor the Hydrocal since it is almost as strong as dental stone, but has a much longer working time. 20 minutes, vs 7 minutes. This allows time to mix well, settle, level, and get the bubbles out. In the end a fast cure time does not matter since you have to wait the same time for either to dry out. Only 5:1 of water by weight is needed for complete hydration but more like 2:1 is required to get a workable slurry. I built a drying tunnel out of an open ended cardboard box with a small electric space heater. I declared the tool "dry" after three days. 

What I did to make a 12" tile tool for a 17":
Roughed out blank face up.
Heavy black garbage bag on top of blank as a release film.
Lay face down one sheet of white ceramic tile, 1" squares trimmed slightly larger than the tool and offset from center.
Pour on about a cup and a half of West Marine epoxy (buy the pumps, its much easier)
Spread the epoxy for full coverage.
Embed the tool into the epoxy puddle, rotating for good coverage.
Use a paintbrush to coat the rest of the tool with the excess.
Put a piece of plastic on the back as a release and put a couple barbells on top as weight.
Pull the garbage back up around the whole thing and tape.
Next day open it all up and use a diamond tile wheel on a body grinder to shape and bevel the edges.
Use a knotted wire wheel on the body grinder to remove the epoxy from the faces of the tiles and to clear the channels.
Grind...............

-- 
Jeff Lowe


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