Info needed: Brake bleed nipples

[Alastair Thomas]

I treated the unused Lockheed slave cylinders on my F60S to new bleed nipples (I do not have the old ones) but however hard I tighten them, they leak.
The nipples I bought are of the correct thread (seven sixteenths UNF) for these cylinders and have the pointed ends (90 degrees included angle).
Should I have bought the flat ended type and inserted ball bearings or are those that I bought the wrong included angle?
The witness mark on the one I have examined closely is a circular line.