The only time your slightly smaller exhaust filter will make any
difference is when you first start evacuating the system and it flows
appreciable amounts of air. After the first 5 to 10 inches of Hg, it
won't make any difference. If you are trying to pull a soft vacumn on a
large enclosure (eg a vacumn veneer gluing bag big enough to hold a
conference table) it will take longer.

Ignoramus14487 wrote:
Don, thanks for your suggestion, I went to home depot and bought a
flare to compression adapter, and compression to pipe adapter. A
helpful HD salesman flared and gave me a small piece of 3/8" tubing.
With all that, I installed a vacuum gauge that I had.

The good news is that the pump pulls good vacuum. The GAST gauge
(pulled from a broken pump a year ago) is very inaccurate, it is not
even zeroed, but it shows vacuum in the "neighborhood" of 28 inches.
That's good enough for pretty much any application for myself, and
likely the pump works close to its spec of 25 microns. Its appearance
suggests that it was only lightly used.

The bad news is that the about 1" piece of copper tubing will
eventually fail from vibration, as it vibrates somewhat and supports a
cross fitting and a vacuum gauge (eventually to be also fitted with a
connector to an air tank, a valve, and a connector to whatever is
being vacuumed).

I decided to not worry about it too much, when it fails, I will think
of something better or may try to use a much shorter piece of copper
tubing, or maybe I will mount the gauge and fittings separately using
plastic tubing. Whatever. There is no safety issue here.

I decided to take a little risk and try a $18.99, five gallon air tank
from Sears. If it collapses, not a big deal -- but I think that a
smaller tank is less likely to collapse than a big one.

I will also try to fit a exhaust filter (to capture oil mist), also a
pull from a rusted 1/3 HP gast pump. Here, I am just a little worried
that a filter made for a 1/3 HP pump, may be in somne ways inadequate
for a 1/2 HP pump. Any thoughts on this?

i