An Odd Thread

[Mike Rometer]

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.

[gondolier88]

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

[Mike Rometer]

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.

[Mike Rometer]

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",

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Just got to silver solder it in place now!

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