RE: ATM 10" blank

["Sam Michael" <samm@idcomm.com>]

Hi Jerry.

I have done what you are thinking of doing.

Contrary to what others might say, I thought it was a pain in the BU*T to do
this.

Here is what is involved.

First Cut a circle out of some MDF board.  Make it the same size as your
intended mirror.

I used a router with a jig I had made in order to cut it perfectly round.

I then took a piece of steel sheet metal, the length of the circumference of
the mirror and about 3" wide and cut some channels into it every 2 inches.
The channels made the piece of metal look like a straight blade with really
wide teeth.  I cut the metal to within 3/4" of the edge (the thickness of my
now round board).  I used an abrasive blade on my circular saw to do this.

I then wrapped the board with the strip of sheet metal and screwed it into
place.

Now comes the tricky part.  You will either have to have a base that turns
or you will have to have a really big drill press (or a radial arm drill
press).  Being a carpenter you probably do.

Run a half inch bolt through the center of the tool and put a nut and lock
washer on it.  Make sure it is really tight.  Chuck up the remainder of the
bolt into your press and Walla.  You now a really big hole cutter with some
rather wide teeth.

Line the tool over the blank and using a sharpie, mark along the edge where
the cut is going to be.

Using RTV, make a dam on the inside and outside of this mark.  Put some
coarse grit (60 or 80), a bit or water and start turning.

Make sure the RPMS are low (about 60 if you can manage it).  In about 20
minutes you should be through the glass (at least that was how long it took
when I did it.

The edge is rough and leaves something to be desired.  It certainly does not
look ANYTHING like the beautiful edges you get from any of the glass
suppliers who send you perfect edges.

The real bummer of it all, is that after I shattered my mirror in an
accident that occurred during the initial stages of polishing, I was so
disgusted by having to cut another piece of glass and make it round that I
went ahead and have both Newport glass and ASM products a call.

Turns out that my piece of glass precut and ground in the thickness that I
wanted was only about $90.00.  ASM will actually pour one for you and if it
is that thin, it just cost less!  I had paid about $50.00 to get the square
piece and went through a great deal of headache making the tool, the mess
and the aggravation of cutting the thing.

I calculated my effort at about 20 cents per hour.  I guess I am not sorry
that I did it, but the only way I would ever do it again, is if it was a
REALLY big piece of glass and even then, I am just not sure it would be
worth it.

Hopefully this is enough information to help you with your project or to
help you decide to buy one, if that turns out to be less trouble.

Happy Grinding.

Sam.

> -----Original Message-----
> From: owner-atm@shore.net [mailto:owner-atm@shore.net]On Behalf Of Jerry
> Dove
> Sent: Wednesday, April 21, 1999 6:30 PM
> To: atm@shore.net
> Subject: ATM 10" blank
>
>
>
>       Hi everyone,
>
>       I'm new to the list and I'm not to sure how to go about this.
> I'm going to try to build my first scope  from  1/2" x 10" sq. plate
> glass, if this is feasible. I've seen posts saying that it has been
> done before, but what kind of problems can I look forward to?
>       Does anyone have any suggestions on how to cut the corners off
> and round the blank?  I tried a ceramic tile saw ( hand held type) and
> it would barely cut it.
>       I'm a carpenter by trade so this is going to be new to me.
> Any advice/ help would be very much appreciated.
>
>       Thanks in advance.
>
>       Jerry Dove
>       Fort Worth, Tx.
>       Partly cloudy and 76 deg.
>