Re: ATM Where do you grind?

[Anthony Stillman <atmer@flash.net>]

Jim,

For me its split between home and the Old Chabot Science Center.  There's
still some question where and whether the New Chabot Space and Science
Center will allow grinding.  Grinding (science) is messy, apparently messy
isn't allowed.

At home I work in the garage and use a Workmate or the workmate knock-off
(different corners) with a grinding / polishing board on it.  The square
base boards have circular boards above them, pinned to spin at their center
on a nail (sans point) and riding on tacks or coin sized taped over nylon
or felt press apply scratch guard pads.  I use three of these pads, the
kind used under furniture, positioned evenly at 60 to 70 percent of radius.

I approach contamination several ways.  I wash the working surfaces just
before they're engaged and cover them if they are left alone for even a
short while.  I spray shellac the tool and workspace every few grits,
always the workspace before moving on to polish.  I use lots of newpaper.
This gets wrapped up, grit side in, and tossed every grit.  Well OK, most
every grit.  Alright! Fine!, every third grit, more often if I've been
messy, oops, I mean scientific.  Incidently I always cover my open grit
container while grinding, even the 60.

Durning polish I wrap or drawer the pitch lap and cover the glass between
sessions.  Also no sweeping or laundray while the bits are out.  The
workmate knock-off is between the washer and dryer.

At the shop, the old shop, we segregate coarse from fine grinding by which
end of a long table work is allowed.  We have a seperate table for
polishing.  We try to instill responsibility in the beginners.  That is,
don't dust off your 80 grit hands over the mirror being worked at 9 micron.
Its pretty much our only rule and most people are accept it.  I usually
intro a newbe this way, "Put a scratch in this man or woman's mirror and
you won't make it to the parking lot alive"  After they've worked through a
couple of grits they become the overlords.

When picking out a space,  I look for a large convenient sink who's faucet
end I can wrap in rubber, secure storage space, enough room for footing and
finally possible sources of contamination.  The last includes looking up.
A ceiling can be a big problem.  Even world renown professional optical
shops can be foolish about ceilings as sources of contamination.  Tape,
aluminium foil, a plastic sheet can save a lot of heart ache, and time
(money).

In practice making sure every thing is clean before any given stage is
usually good enough.  The old adage, grind more worry less, is still true.


Anthony