Re: [ATM] sharpie test (Fine Sharpie Test)

["Tom Moulton" <tom@moulton.us>]

> After reading different information about the sharpie test when ginding
> a mirror, I wonder why a line from edge to edge on a mirror or tool has
> to disappear at the center and the edge of the mirror (or tool) at the
> same time. Mirror- and toolcenter are always in contact with each
> other, the edges are not, so the line should disappear at center first.
> I can understand, that there should not be much difference in time
> though. Do I overlook something?
>
> Jan
> http://home.wanadoo.nl/jhm.vangastel/Astronomy/
>

When the line disappears all at once it proves that the tool and
mirror have exactly the same shape and are in 100% contact.

And at this point you have a sphere which you need to keep
until you figure, keeping one is easier than finding one.

Easier to find/make one when using 25 micron vs 9 or 5 micron

tom
gotgrit.com


_______________________________________________
ATM mailing list http://www.atmlist.net/