This is just a guess Gary – so i may well be shot down in flames!

The Stuart S50 is an old design – it has been around for years as has much of the Stuart range. Nothing wrong with that I hasten to add and generations of model engineers have been introduced to the hobby by the Stuart brand. At the time of their introduction pretty much all "stuff " was imperial and threading equipment was plentiful and relatively cheap. That is not the case now and my suspicion is that you are paying a premium for the unusual size.

I guess you know that both1/4 x 32 and 1/4×40 are available from Stuart see HERE or Tap & Die HERE or even cheaper! Tracy Tools HERE

Good luck!

Norman

Thank you Jason – I apologize . **(Note to self –  in future engage brain before posting !) 

As you say though pretty easy to make so, with a 1/4 x 32 CS die from Tracy at £3, that's maybe a cheaper option.

Norman

Edited By NJH on 11/10/2013 17:58:48

Hi Gary.. The Stuart S50 is a lovely engine. I first made one back in the 60's when the machined kit was 5 Pounds..!! Still, as a young apprentice, that was about a weeks pay. I still have it. The sliding valve block is quite loose and depends on steam pressure to keep it seated. This means you need more pressure than the engine really requires to run it. I filled most of the fingers of the block with soft solder and then filed it out until the block was reasonably snug against the port face. The innocence of youth.. haha.. The engine, once hot , will tick over at only a couple of psi with this modification. As for the threading, I prefer the older 32 tpi pitch. The finer the thread, the more likely it is to strip. And the fittings..? Don't make anything you can buy. Cheers from downunder.

Gary,

I have checked some old drawings for a Stuart No 10 engine from about 1963 when I first made one. The threads in the cylinder and valve chest cover are both 1/4" x 32. I guess the reason is that the courser thread will be less likely to strip when tightening up the steam pipes/unions. I cannot explain the difference in price – have you tried asking the current owners of Stuart Models?

Eric