RE: ATM Rough Grinding

[Bob Prabowo <BOB@bahana.co.id>]

Hi Larry,

        1.Should I be doing a W stroke?  
When I rough ground my mirror, I used a 6" cement tool covered with
coins, and 1/3 COC stroke


                2. I can crush the grit in about 2 strokes I notice it
lasts a little
                longer when it is just damp - when it is wetter it goes
to mud very
                quickly. I am shaking grit on every 3 to 4 strokes and
with the 5lb
        weight I push down with 10 - 20 lb probably

The way I did it, I only put a small amount of water, just enough to wet
the mirror. After 2 or 3 wets I washed the mirror wiped off the water
left on the mirror and spray some abbarsives. I didn't add more water
because the water left over from the washing was enough. 


        3. What does a 'wet' consist of? 
After a few strokes the abbrasives will be crushed and you either wash
the mirror or add more abbrasives. I think that's a "wet".


                I am at about .050 sigitta and have used 3lb of 45-70
grit.

I started with #60 grit and it didn't take that much of abbrasives to
get to 2.5 mm sagitta. One of the things I learn from my previous mirror
(and from the advice from the list member) is to not to use too much
abbrasives and just a small amount of water. For each wet I only use a
half tea spoon of abbrasives (the finer the grit the less you use) and
to spray the water I used a hand pistol sprayer (is that the name?), I
only use one spray of water for each wet.
>  
> 
                I notice that depending on how I place the straight edge
across the
        mirror the measurement can change i.e.I have ground some of the
mirror egde     off I think

Don't worry about that, you will have to grind the edge later anyway.
Hope this helps,

Happy grinding,

Bob P. Sumitro
Jakarta, Indonesia