Re: ATM Where do you grind?

["Bill T." <twentiethwave@hotmail.com>]

Jim Dolson wrote:
> I am curious where everyone grinds their mirrors - especially their large
> mirrors (16" on up).
>
> After completing my 6" f/8 rebuild, my brother and I are considering
> grinding a 16" f/5, but the only place that we could do it is in the
> workshop of my barn.  It is an insulated room, with a door seperating it
> from the rest of the barn, but I'm concerned about contamination.
>
> Does anyone grind in their garage or barn?

I grind and polish in a space with machine and wood working tools.  Metal
particles, sanding grits, the whole works are everywhere.  I have polished
while others were sanding nearby.  But I haven't had a serious scratch in
years.

As John Dobson pointed out, "grits don't have feet."  If everything you use
is clean to start with, you won't get contamination unless it is transported
in.

Before polishing I make sure I have clean surfaces for my tools and
materials, and that there are clean supports for the mirror and tools when
they are not being used.  I cover all table surfaces I plan to use with
plastic trash bags.  I restrict myself to touching only those things I know
are clean, and I make sure I don't put any item I'm working with down on a
"unclean" surface.  I don't hold the bottom of any container directly over
the mirror or tool.  If something falls on the floor, it either stays there
until clean up time, or I clean both it and my hands at the same time.  It
helps to have a deep bucket of water to remove grit from your hands so you
don't spread it around the shop -- if your hands get gritty, rinse them as
soon as possible.

During grinding I reserve a particular table to hold the grits.  I cover the
table with a plastic trash bag, which is carefully changed for each grit.
When I change grits, I put all the old grit cups, plastic spoons, whatever
in the center of the bag and then fold it up. I use a wet paper towel to
clean grit off my skin during grit changing procedures.  All wipedown towels
go from use directly into the trash can.  I never wipe my hair or clothes
with my hands.  I make sure the water faucets in the bathroom are rinsed
down.  I wipe down all the doorknobs I might use.  If I go from grinding to
polishing on the same day, I take my shirt off.

Probably most important, before getting my hands into the process I wipe my
fingers together to feel for grits.

If the phone rings and I pick it up with gritty fingers, I carefully wipe it
down afterwards.  Things like that tend to get you.  If the UPS man hands
you a package, clean up.  The trashcan can be a sneaky menace.  Visitors are
unconditionally unclean.

You can take the cleanliness thing as far as you want.  The above is what I
do.  It seems to be enough to control things in an environment that would
chill the blood of most professional opticians.

I personally wouldn't bother with the plastic roof sheet thing, unless your
roof shakes.  And I rarely mop the floor which is often quite barn like.

Bill T.