View Full Version : "R1/4" thread. What is it?

26th May '11, 13:47
I need to fit this (http://uk.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=686-2627+&x=26&y=19#header) part (pictured below) to something. It has a "R1/4" thread. Anyone know what that means? Is it an ordinary 1/4" BSP thread or is it some kind of fancy thread with non-parallel sides?


27th May '11, 10:19

The 'G' and 'R' thread designations were added when BSP threads were adopted by the metric system for pipe threads.

'G' is the same as BSPP (parallel thread), 'R' is the same as BSPT (tapered thread).

27th May '11, 17:43
Thanks for the help. I had some samples come through today in the post. The overall diameter of the thread measures more like 1/2", so I'm pretty confused about the "1/4" designation. I made some measurements in metric: the diameter of the thread is 12.9mm at the top, tapering up to 13.3mm at the base. The length of the threaded part is 11mm. I'll drop the samples off to a machinist on Tuesday. Hopefully he can cut the right type of female thread for me.

27th May '11, 17:54

BSP Pipe threads are sized according to the thread that can be machined onto that size bore pipe, so a 1/4" BSP thread measures 0.518" or 13.15mm

Tapered threads are used when a shoulder is not available to seal against like threading the OD of a pipe and should be screwed into a female tapered thread.

Tapered threads are prone to leakage but have the benefit of being positional.

3rd May '13, 11:46
Look at this...
or this