The Steamboating Forum

Hi Guys, perhaps one of you can throw some light on this one. I bought some standard plumber's compression pipe fittings and wanted to screw them into a manifold. The pipe size is for 10mm, or 3/8", the difference is so small that the olives will close easily.

I tried then against 3/8" BSP and they are too small. On measuring the outside of the existing thread it is as near as d*** it 15mm, or roughly midway between 19/32" and 37/64" (niether helpful sizes with threads). So going with the 15mm (also not a common size) I expected 1.5 pitch or maybe 1.25. Not so; either of them?? The thread appears to be of Whitworth profile at 19 TPI which might indicate a 5/16" BSP but as far as I can find there ain't no such animal. Any ideas out there?


Puzzled of Middle Earth.

Common on metric fittings- if you want 3/8 bsp you need to get 3/8" fittings.

Air conditioning and pneumatic suppliers are the best value usually- I use airlinkcompressors.co.uk for most of my stuff, but ebay can be useful too.

Greg

Hi Greg, I wasn't fussed particularly for the 3/8" BSP thread (though useful, as I do have the taps and dies), I just wanted to replicate the thread on the fitting, as being the easiest option. It seems an expensive way for a manufacturer of thousands of fittings to go, using a non std. thread like 15mm x 19tpi Whit profile. I thought I must be missing something. He must consider that the brass saved is worth the extra threading costs.

They say that cats have nine lives, there is also more than one way to get their fur off!

Turned the thread down to a thou or six less than 9/16",
Just got to silver solder it in place now!