At the risk of sounding like a stuck record (if you are old enough to know what that means) scrap those ratted out cylinders and buy new ones. You will be light years ahead in reliability.
If you are determined to rehabilitate the old ones do it right - grind/cut
ALL of that buggered up rusty mess off right down to the hole in the barrel and weld/braze on new pre-made oring ports.
This 90 degree weld-on port with SAE 6 port is designed for quick field maintenance to get your cylinder up and running. Shop now!
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This weld-on port with SAE 6 port is designed for quick field maintenance to get your cylinder up and running. Explore today!
www.baileyhydraulics.com
Dan
First, I agree. Replacing the cylinders will be the best overall and long term. Even if the OP gets them working, I'm not sure how well they would hold up...
However, it sounds like the OP can't (or doesn't want to) replace them right now (cost, time to get new ones, is enjoying rebuilding them), and will get new ones on down the road. When he gets tired of rebuilding them. Continually. :}
Grinding off those old ones would be the correct approach! When I suggested possibly using reducing fittings to get it down to a common size, I said you'd have to bore the old ones out, tap and then insert a fitting. Then I saw what you were working with, and realized boring out won't work because you probably won't have much metal left!
New weld on fittings look best. And cheap, too! Grind the old ones off (shouldn't take long, there doesn't look like there is much left) and then weld on new ones. If you can't weld in-place (I wouldn't), take them off. Prep the metal and fittings, take it to a friend who does welding.
I (personally) don't think brazing would be strong enough for holding two parts together without a mechanical assistance (threads), but that's just my lack of experience with high(er) pressure systems. I'm sure others will have a better idea about that than I will.
Good luck!