William Noble wrote:
if you recall that one atmosphere is 14.7 PSI, this chart will help:
http://www.britishmetrics.com/html/pis-bar.htm
and if you further reacall that one atmosphere is 30 inches of mercury
(aprox), then it should all be obvious. You don't need a vacuum less than
.07 bar or so, that's 70 milibar, or 7X10E5 greater than the value you have
below. You REALLY REALLY REALLY do NOT NOT NOT want a high vaccuum pump.

you may find my article on vacuum pumps and chucks helpful - you can
download it from my web page (www.wbnoble.com, click on vacuum pumps) or you
can download it from the tips section of www.woodturners.org - it's the same
article both places.

bill (not in Detroit)


Thanks, Bill. I don't think I've needed to know either of those numbers
more than once or twice since graduating from High school in 1970. And
possibly stretching all the way back to Jr. High.

I see various units offered in the catalogs, your offerings, and the
other offerings on the internet and I was trying to puzzle out just what
sort of unit would have more than enough suction without sucking all the
money out of my pocket or requiring an underground bunker for noise
abatement.

Out of curiosity, how far away from what I need would a good shop vac
be? I mostly want to finish turn the bottoms of bowls in the 6-10" range
with flat edges that have already been sealed.

Hmmm ... maybe I could put a barometer in a wooden box with a plexi face
and test for myself. That should be good enough to give me a ballpark
feel for what's going on.

Bill
--
I not only use all the brains that I have, but all that I can borrow.
Woodrow Wilson (1856 - 1924)


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