Try 'hydraulicsupermarket.com' for the hydraulics, and Norgren for pneumatics. You can also do a web search as there are plenty of on-line courses - a lot of them free. Good luck!
When I was 'on the tools' many years ago, I worked in controls as applied to the oil and gas industry. Swaglok and Parker were the main suppliers of SS tube compression fittings. The fittings suppliers also provided SS seamless tube in varying diameters and wall thicknesses to ASTM A269. The...
Not sure how to answer this one. For instance, what kind of oil are you proposing to use? Car engine oil is the obvious answer, and if so, go to one of the manufacturer's websites and you will get all the technical info, viscosity, density, etc. you can handle. Good luck.
Years ago when I was a lad and the price of beer wasn't through the roof, metal to metal sealing faces in valves of various descriptions did not have allowable leak rates on test. They were classified according to their ability to stop whatever was in the line from passing - especially gas...