Sulaiman - 19-8-2015 at 00:38
I have just had an operation to replace the lens in my left eye
so it was very easy to turn a blind eye to the cost and treat myself to a rotary vane vacuum pump. 
I bought this one http://www.ebay.co.uk/itm/301433571046?_trksid=p2060353.m274...
Specified 3.5 c.f.m. or 0.3pa (2.24 um Hg) ... sounds good 
Can anyone identify/name the two connectors used on the vacuum inlet port please?
My best guesses at the moment are;
upper: M 1/4" SAE for refrigerant R12 systems (pre-1994, Freon12)
lower: M 1/2" ACME thread for refrigerant R134a systems
[Edited on 19-8-2015 by Sulaiman]
DJF90 - 19-8-2015 at 02:37
Being that the pump is marketed for the HVAC market, these are probably connections that are used with refrigerants as you suspected. The top does
indeed look like 1/4" SAE and the lower I am unsure of. One thing you may prefer to do is work out what connection the adaptor makes to the pump, and
buy a hose barb adaptor with that thread type. Thats what I did with my Javac 10.8 cfm pump anyway...
Sulaiman - 19-8-2015 at 03:33
Assuming that this pump has some sort of guarantee,
after it expires I intend to change the inlet port as you suggest or similar.
Not much point having a 0.3pa pump at the end of a long thin hose.
Since I neither need nor expect 0.3pa, I will use the supplied connector for now.
A quick test using silicone tubing (reportedly poor below 50um) and a cheap bourdon vacuum gauge;
almost immediate vacuum of -0.1 Mpa = -1 atm = good.
DJF90 - 19-8-2015 at 06:14
Switching the adaptor out for a hose barb should not affect the guarentee. I doubt you'll get lower than 0.1mmHg on a working system, but its a very
practical vacuum.