Info needed: 9.00-16 tube stem size?

[Russell Boaler]

On the subject of tube stems I've got a couple of 1100x20 tubes that are 50 odd years old that I was planning to re-use but the threaded tip of the brass valve stem is damaged (uneven face) and a normal air compressor connection won't seal on it (one of the dangers of having the valve stem extending too far from the rim I guess). I could file the end down to achieve a flat sealing surface but then the tip of the valve will protrude out from the valve stem which isn't good either. Does anyone know if there's a tool available out there that can re-cut the valve seat deeper into the valve stem?