From: Guy Brandenburg 
To:  atm{at}shore.net
Reply-To: Guy Brandenburg 


I just recently combined some ideas I had gleaned at Stellafane and the 3rd
Delmarva Mirror-Making Seminar and came up with a sort of a turntable for
grinding and polishing, so that it is easy to actually get things to rotate
a full 360 degrees in any increments you want, without having to have a
barrel full of water that is trying to grow mosquitoes.

All I did was to make a square box out of old scrap 2 x 4's, about 1 foot
on each side, nailed or screwed together. The box stands about 3 1/2"
high. On top of that I screwed a square piece of scrap plywood (3/8"
thick or better) to make the top of the box. If the plywood was a bit thin
(like the 3/8" is), I nailed another small piece of wood on the
underside, to provide more wood. I then screwed a drywall/carpenter's screw
into the exact center of the square top, but left about 1/4" of the
screw sticking out.

Then I took another piece of plywood, at least 1/2" thick, but
preferably more, and either cut it into a circular or octagonal shape
(whichever is easier). On the underside, I drilled a shallow hole that the
head of the sticking-up screw will fit into - obviously it should match the
head of the screw.

Then I attached the cleats for the glass to be polished on top of this
piece of plywood.

The whole box can be attached in some fashion to your workbenches. If you
want, and if the height of the tables is already satisfactory, you can omit
the 2 x 4s, and just have the plywood-on-plywood turntable, and use a C
clamp to clamp the under-neath piece to the table. In our case, the
carpentry tables were seriously low for almost everybody's back except for
the 5th graders, so the extra height was really helpful. We have
woodworking tables, like I said, that have woodworking vises (or is it
vices?) so a little piece of trim nailed along one bottom of the box works
just great.

No photos yet, but here is some wonderful ASCII art.
           (=+              +=)           <<-- the cleats
      +------------------------------+
      |           +---+              |     <<-- the turntable, w/hole
      +-----------+ | +--------------+
  +-----------------|---------------------+
  |                 |                     |  <- the bottom piece, with screw

You don't want the turntable to wobble at all, so the screwhead  should fit
nicely in the hole, but be easy to take off and put back on. You don't want
to lubricate anything, or to use Teflon and formica, because you only want
things to rotate if you MAKE them rotate. So wood against wood is good.

My ASCII art shows a gap between the top piece and the bottom, but it is in
fact not there.

Guy Brandenburg

Jeff Anderson-Lee wrote:
I started my grinding at Chabot.  They don't have drums there, just
standard science classroom workbenches.  I found that by standing on the
corner I could work my way around 180 degrees before picking up the whole
piece and turning it.  Granted that was just with an 8 inch mirror and
tool.  However I regularly see people working there with up to 16 inch and
occasionally larger mirrors with no problems.

That's not to say that having a drum would not be nice, but you are going
to need about a 6x6 to 8x8 ft2 area to use it in.  If you have that, great!
If not, consider the corner of a sturdy workbench.

Jeff Anderson-Lee
Sacramento, CA

From: "Glenn Becker" 

Okay, I live in Brooklyn, NY ... er ,,, where might I find a big ol' oil
drum (empty) to use as a grinding stand? I mean, what sort of place would
even *have* such a thing?

I know this is simple sounding, but ... :)

Grinding on the floor has gotten old, and I anticipate future projects.

--- BBBS/NT v4.00 MP