[ATM] Re: grinding and polishing a 32"

[Hugues.Laroche@ses-astra.com]

Hello Mike and all,

> I suspect that a 2/3 sized pitch lap on a 45 inch
> disk would be, well.....A TOUGH PULL!  I figure
>that is about a 30 inch tool! That's big for hand work.

You are right. However I worked with polishing pads whcih provide a
less viscous contact and a very consistent drag. So yes it was hard,
but quite predictible - had the feeling to push, say, a small car with
help of somebody else. End of fine grinding at 9 and 5 microns
was another story, enormous drag, had to push as strong and regular as
I could, but the problem was to have it moving ALL THE TIME, because
it tended to stick in a few tens of seconds of stillness (while reaching
for the spray bottle or preparing to unload the tool from the mirror).
That's why my last pass at this step (had to come back 3 times to fine
grinding) was done in one long spell from 15 to 5 microns without
intermediate
cleaning. Useless to say, I was completely exhausted and wet afterwards.

Lawrence, I also suffered from an hernia problem, probably not related
to the big glass, but for sure the healing put about 3/4 year delay in the
project.
I am now going to machine, partly because I cannot progress substantially
by hand (the figure does not change appreciably) and also because
I do not want indeeed to break something (well, while making the machine
I succeeded to drill into my arm this week-end - conclusive, flesh is
defintely
softer than wood - so even making a machine can be unhealthy)

Dont do like me, take care,

Hugues




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