ATM Re: Making first tool

[Dave McCarter <McCarterD@claven.fanshawec.on.ca>]

Cathy wrote:
>       I haven't been able to find 1" tiles at Home Depot, and
>haven't tried Color Tile yet, especially since there have been comments
>about the softness of the tiles there.

One trick which has not been talked about much is to use small squares of
plate glass instead of tile. This I think would be useful if the depth of
the mirror curve is thicker than the tiles available. Also nice if you
can't find suitable tile. I will shortly be cutting some 10mm thick plate
into ~ 1.5  inch squares, using a glass scribe, a wood vice, a pot holder,
vice grips, and safety glasses. I plan to roughen up one surface to improve
the grip of the epoxy. This will allow going to a deep sagitta on a big
mirror without the fuss of laying new tiles on top of old, and having to
work them in. I'll report on how it works later.

Some tile stores still carry sheets of six sided tile, maybe 1.25 inch
wide, which were popular for floors. They are quite hard. I bought a box of
twenty sheets for $20. The store was glad to see them go.

>Is it safe to use the 1.5" tiles I've bought? 

Sure. And you can get a nipper tool, sort of an edge cutter plyers with the
cut at right angle to the handle, to clip off the unwanted edge. A belt
sander, grinding wheel or sharpening stone can be used to round or bevel
the edge to prevent chipping or cutting yourself.

>I intended to hacksaw them down to 1", but
>without a vise it is extremely difficult to hold them still well enough
>to cut.

Boy I can sure believe that!

>I am struggling with a method to hold the tool/mirror in place for
grinding.  

I cut some 1" nylon dowel into 1.5 inch lengths, (I am working a 2" thick
glass), drilled a hole down the axis just big enough to pass a #8 screw,
enlarged the top end of the hole with a bigger bit just enough to recess
the screw head, and screwed this cleat into the top of the mirror support
board. With screws I can move the cleats easily. Nylon does not scratch
glass, and the metal screw is hidden so does not pose a threat to fingers
or glass.  No nylon? Try plastic drawer knobs instead. Some have built in
screws, most need to be drilled to accept a screw.

>My original plan was to nail two pieces of 2"x4" into my workbench (which
also >will double as grinding stand).

You might want to consider using a piece of 3/4 inch plywood just a few
inches larger than your mirror, which can be clamped to the table, screwed
into easily, and removed for cleaning. Then your nice bench does not have
too many holes in it. :-)


David McCarter   McCarterD@claven.fanshawec.on.ca
R.A.S.C. London Centre VP & Observers Chair,
Amateur Radio VE3GSO