rear triangle replacement

Thanks for the reply, unfortunately Rudge frames are very much imperial, a 9mm axle is too big, it needs 5/16". The logic behind the original question is thus: i have used a 5/16" axle on a rear hub designed for a 3/8" as there is no readily available fixed hub with the right axle. This has led to problems setting the cone adjustment and I have found that even the slightest movement of the lock nut translates into alarming play at the wheel rim, coupled with the fact that the balls fall out with only a little bit more gap on the cone, it does not lead to worry-free riding. The other problem is that the BB cups are worn but due to their 26 tpi thread, are hard to replace. My original thought was to file open the dropouts and wait for a BB to turn up, however due to the angle of the dropouts, filing will reduce the available lateral adjustment. I then thought, perhaps I could replace the dropouts for conventional fixed/track ones, however I suspect getting plug ones to fit the odd sized tubing will be more of a headache than getting an axle. Then I thought if I replaced the whole rear triangle with the BB the whole thing would be much simpler, I was going to dismiss this thought as ridiculous but before doing so I googled it, whereupon I discovered Mercian will do such a job. My reaction to this discovery was, well Mercian charge about 5 times what the actual frame is worth but if they can do it, maybe I can; hence the question. In reality I am unlikely to take on such a radical project and I will probably file an axle to fit and suffer a noisy BB for the foreseeable future, however I thought it'd be interesting to ask if anyone else had trodden this road.