If you are in the US it is probably much easier for most readers
to buy a surplus non lubricated compressor than to fool arround
with old refrigeration machines. In the US you can find either
surplus new or take out used Piston and diaphram machines from a
few surplus dealers. Surplus Center in Lincoln Nebraska is one
dealer. 402-474-4055 1-800-488-3407 to order. In a flier I got
today they list: Thomas Industries , 1/3 HP 1.4cfm at 100 psig
compressor at $69.99 catalog #4-1421 this also works as a 4 cfm
vacuum pump at 27.9" Hg.
Thomas Industries 1/8 hp, 1 cfm at 40 psig for $ 39.99 catalog
#4-1444 Also works as a 1.6 cfm vac pump at 27" hg