I tried to bleed my clutch system today. It was going well until the connection of the metal pipe to the hose going to the slave cylinder started leaking.
The metal pipe is the original steel one (51 years old) , and the hose going to the slave cylinder is new.
I think a new copper pipe would bed into your new flexible hose end more easily than a steel one. If you are keen on keeping the old pipe for originality there is a sealer for such joints available from Frost Auto Restoration Techniques, http://www.frost.co.uk It's called brake & pipe sealer.
This happened to me when I replaced the flexible hose..It turned out the female end of the hose was longer than the old one, so the end of the metal male pipe could not seat properly.
I cut a piece off the end of the flexible pipe and all OK...
I once bought a new flexy hose, it had a scar, in the conic part, where the male pipe is suppose to seal (poor fabrication) .
I made a small cobber washer, put that into the hole, and all was fine