Quite so, Mario. There is no criticism from me of your work. I need to replace the O ring because it is old and does not allow the ram to be pressurised. I may look at other designs of O ring, which may make a better seal.

The ram doesn't move smoothly. The problem is not the O ring seal, but the piston catching on the plastic (nylon?) seal which is inserted in the top plate of the ram. I have sanded and smoothed the ram and the plastic seal to improve the movement and will do some more to allow the ram to move freely.