Snapped the valve off my Marzocchi 66 SLs whilst applying surprisingly little torque in the wrong direction - what a pillock.
That's after I'd tidied up the ends, by the way. So after a lot of thinking and experimenting with inner tube valves, I decided the best thing to do was to glue a smaller piece of tube between the two broken parts and cross my fingers. Problem is that the bit had sheared off right where the end of the valve core was inside. I realised that the stem of a threadless presta valve inner tube had the correct internal diameter to accomodate the end of the schraeder valve core, but the outside diameter was too large. So I needed to turn the part down a bit on my lathe.
But I don't have a lathe, the only turny thing I have is a pillar drill.
This worked surprisingly well. I kept measuring it top and bottom with a micrometer, and got it down to 5mm within a few hundredths. I hd already drilled out the broken off valve bit with a 5mm bit so I kept trying it til it was a good snug fit.
Now the only problem is how to hold the damping rod to drill out the hole in the end. I drilled a perpendicular hole in a block of wood held in my hand vice so I could stick the rod in it and get it perpendicular also. A bit of water on the wood ensured a snug fit there.
It fit, so I glued it in place with Araldite metal epoxy. All I can do is hope that it withstands the moderate torque and tension of tightening up the bottom bolt.