I have disliked most of the solutions to machine lubrication for us hobbyists. I have of course seen some beautiful work and ideas from many here. However I just did not like the fittings and their bulk etc. Many fittings are just too large and in precarious locations just inviting collisions. Also the Chinese ball screws come with a Zerks fitting of some kind that have an additional benefit, they are 1 way or check valve. They are also very small.
I had a piece tubing that just fit over the Zerks fitting. When pressed on the fitting, the tubing has a larger OD. I then ran a nut the size of the tubing's original OD all the way to the expanded area. Upon tightening the nut it created an incredible fit. Having a few other fittings around, I pressure tested this arrangement. I was able to exert 120 psi with no failure. I could have gone higher but would have to had cycled my compressor again and saw no need,
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How about a video?
Cheap pressure fitting Pt 1 - YouTube