Anyone good with thread identification ?

[CRS51]

Evening all, I'm trying to find a thread type that is used on my 1958 Leyland recovery truck air system.
It is a very fine thread and the only tap I have that matches up is a 7/8" with 26tpi. Anyone hazard a guess to what that is ? I had a quick search and all I can find is a reference to the old BSB thread but these a re steel pipe fittings.
Cheers Chris.
P.S. Ill get some pictures tomorrow evening.

 

[MattH]

Is it 7/8th 26tpi?

 

[CRS51]

Is it 7/8th 26tpi?

Yes MattH one of the sizes matches up with the 7/8" 26 tpi tap I have and one of the other fittings that measures 1.370" O.D. also matches the same thread pitch.

 

[wyn]

"brass pipe screw thread" BSB?

 

[MattH]

So it’s 1-3/8” 26 tpi.

Could be BSC.

 

[CRS51]

"brass pipe screw thread" BSB?

I think so Wyn

 

[wristpin]

Maybe worth browsing the Tracy Tools website.
https://www.tracytools.com/

 

[Popcorn]

Check if the threads at a 55 degree angle, if so there a 'Whitworth Form' special. Used on a surprising number of Austin/Morris/BMC vehicles.

 

[mechman]

Cycle threads used to be 26 TPI but not sure if they went 1-3/8"

 

[CRS51]

Maybe worth browsing the Tracy Tools website.
https://www.tracytools.com/

Thanks, they are listing 2 types of thread with 26tpi (BSB and BSC)
I will take a picture later and post it up,
Cheers

 

[Keith 66]

The flexible brake hose on Moggie 100's use that thread on the end of the hose to attach to the bodywork, of course they are always seized solid & new hoses dont come with new nuts. Always a pain.

 

[MattF]

Check if the threads at a 55 degree angle, if so there a 'Whitworth Form' special. Used on a surprising number of Austin/Morris/BMC vehicles.

That would just be BSB, would it not, at 55degrees? BSC is 60degrees? Just working from memory, so I may be off mark.

 

[Stueeee]

That would just be BSB, would it not, at 55degrees? BSC is 60degrees? Just working from memory, so I may be off mark.

yes, BSB and WF both 55 degree threads. BSCy is 60 degree angle. As said, lots of odd Whitworth Form threads on BMC stuff; one particularly irritating one is the 5/8" x 16 TPI used on the front of their crankshafts.

 

[CRS51]

Thanks for the help so far, here are some pictures I've just taken
Cheers

 

[mechman]

Makes you think what was in their minds when they created oddball stuff like that when so much more compatible stuff was on the go.