I have two long series 1/4" drive sockets that have fitted everything that I have come up against in the recent past with a hex nipple and they are 1/4" AF and 7mm AF. Even if they are slightly loose if one holds them very firmly and dead in line with the axis of the thread they spin the nipple out just fine.
I find that the 1/4" AF nipples are often very restricted in clearance around the nipple so I have turned this one down to about 0.020" wall thickness and now have no problems with it. It pays to invest in a nice little 1/4" drive tommy bar to go with these sockets as you can then really get your hand wrapped round it and it isn't off to one side as with a ratchet.
The square headed nipples used by Purdey and others are a different problem completely. The trade nipple key for these is often simply a two sided wrench on a turnscrew handle. They are really easy to make from a long series socket as above of the correct or just under AF size. Then simply file a slot straight across the socket leaving 2 opposing flats only. Only file as deep as you need to fit the nipple as the tendency is to splay the flats apart in use.
