Thread identity

[George Dennis]

Hi everyone,
I have one of those small GM car tyre compressors, I've found the thread on the brass end of the hose has been damaged having a lathe I am going to make a new one but I can't seem to work out the treads, would anyone have one of these or happen to know with the thread is please
Thank you

 

[Seadog]

Is that the same as the valve thread? If so it's 0.305 x 32tpi.
Taps are available, but not cheap.

 

[voipio]

Is it the same size as a Schrader valve? Try a valve cap on it, to see if it fits.

PS Snap, Seadog

 

[George Dennis]

It is slightly bigger than a tyre value cap

 

[Erie Fred]

Looks like for adding freon to the A.C.

 

[George Dennis]

I've managed to take a picture if that helps

 

[voipio]

The thread OD is a start. Next thing to do would be to try to measure the thread pitch, using a thread gauge if there's room, or getting an impression by pressing something like a piece of rolled out plasticine or blu-tac onto the thread with a flat bladed screwdriver, and carefully lifting it off. Possible "standard" thread candidates to consider at the moment are: m8 fine, at 1.00mm pitch (or 25.4TPI); 5/16" BSF at 32 TPI, 5/16-24 UNF at 24 TPI. The imperial threads all have a nominal outside diameter of 0.3125" or 7.94mm, so it may be a custom thread.

 

[nickk]

Your avatar,how can Mid Wales be England?

 

[George Dennis]

I've updated my avatar for you nickk,

Well thank you to everyone who helped, I would never have thought about using blue tack, I've now worked out it is 5/16th 32 tpi
Many thanks again
George

 

[RWD3M]

I've updated my avatar for you nickk,

Well thank you to everyone who helped, I would never have thought about using blue tack, I've now worked out it is 5/16th 32 tpi
Many thanks again
George

I doubt it's 5/16", your measurement of 8.12mm is a good bit over 5/16" (7.9375mm).

1/8" BSP would normally be a contender where pneumatics are concerned. But it has a major diameter of almost 10mm so that is probably not a contender either.

Depending how damaged the female end is, might you get a better idea from that?

 

[voipio]

A few folk on the forum have something like this:

https://www.amazon.co.uk/Kochenty-Nut-Bolt-Thread-Tester/dp/B0CYPV8Z82

 

[George Dennis]

I'm not so sure now? I've just measured the hose and found the thread is 30 tpi? As you can see the hose connector has a bigger inside diameter

 

[voipio]

It could be a tapered thread, or an extremely bad fit. How about just sticking the connector on with Araldite, or similar?

 

[RWD3M]

How does a 28 TPI look on that? Will the thread gauge go down the inside of that female fitting?

That 8.19mm is at odds with your earlier measurement on the male end. My money is on 1/8" BSP.

 

[tigdlo]

Are you measuring accross the flats rather than the thread? looks like the threads are die cast rather than cut, the flats are a part of the mould. That would explain the id of the pipe fitting.