Re: ATM 500 grit done, what next ??

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

When you do a wet on a tile tool you do not need to "fill the channels" with
grit. The fine grits, say 500 and down, can be premixed as a thin slurry in
water, and poured on or "painted" with a brush. There will be enough water
and grit slurry bubbling around in the channels to act as a resevoir to
resupply the surface with fresh fine grit.

If you opt for a brush, be sure to use a seperate brush for each grit size.
And beware brush rust which is a super source of scratches. I keep the small
plastic pop bottles to store premixed grits, and just pour a bit on the tool
centre.

Most amateur mirror makers do not fine grind nearly enough, shown by the
very many discouraging hours required to polish out the grayness at the
mirror edge.
I would rather do ten wets of 5 micron AlO and save ten hours of polishing.

I have never seen a tile tool scratch if cleaned well between grits, do the
fine grinding with mirror on top, and keep the mirror and tool edge
carefully beveled.

One recomendation I have read but never tried is using turps instead of
water for the fine grits, say 600 and up. Doesn't evaporate quickly, cooling
the mirror and leading to sticking, turned edge, etc. Of course you can't
try this on a pitch lap as it would lead to a very sticky mess.

___________________________________________________
Dave McCarter      McCarterD@claven.fanshawec.on.ca
Amateur Telescope Maker: Mirrors, Flats, Pitch,etc.
Observers Chair R.A.S.C. London Centre
Amateur Radio Station VE3GSO