Has anybody found a simple way of curing leaks in taper-cock gauge glass blowdown/cylinder drain valves? I'm referring to the conventional bronze bodies and stainless cocks.

It seems that grit gets in and creates grooves in either or both tapered parts, and dribbling commences.

"Grinding in" a leaky fitting only seems to move the grooves to new positions, and excessive metal removal will move the cock axially, so the cross-hole no longer lines up with the fitting.

A PTFE insert might work (either tapered or as a conversion to a parallel cock) but it would be a bit twee and I've no confidence in such an insert not rotating when it shouldn't. – it needs to be fixed to either the cock or the valve body.

Other than making a new cock to suit the reamed-out hole in the fitting (You did remember where you put the reamer you used to make it, didn't you?) does anybody have any bright ideas?