Re: ATM Newbie with a problem (flat spot on tool)

[mdholm@telerama.com]

>If the tool and mirror are passing Sharpie tests, do I need to go back to a
>coarser grit?

No!

Those extra 5 wets might be a good idea since it is possible the center of the
mirror wasn't receiving as much action as it should have.  You might not have
ground through all of the pits from the previous grade in the area that only
recently came into contact.  Also, the extra wets will help make sure you have
gotten rid of any non-spherical shape.

When you do the sharpie test, it may work better if you only do a fraction of a
normal wet, so you can see the ink remaining on the mirror more clearly, but
basically, if the ink is being removed evenly from the surfaces of both the
mirror and tool, you have what you need as far as contact and sphericity are
concerned.

It was a frustrating problem for you, especially with the attention span of
children involved, but you learned some useful lessons from it and will be more
confident as you move forward.

Mark Holm
mdholm@telerama.com