Primus 1020 Pump NRV thread?

Finally I found out why my Primus 1020 was leaking pressure, the threads of the pump tube to accept the NRV are different than the correct NRV housing, does anybody knows what is the thread size and pitch?...

 

M8x0.75

 

Thanks Conny!...will see if I can find it today.

 

M8 x 0.75 are cheap enough over here , around £5 for the cheaper CS taps/dies ( which is fine for cutting brass )

Hope you get sorted

Cheers

 

My local hardware store was closed, so I will check tomorrow.... small towns have their quirks.

 

I would believe that M8*0,75 is closest that you can buy easily. Maybe correct is 8mm and 34 tpi since standard metric threads were not there when they started to make these type of NRVs' more that 100 years ago.

Couple of years ago I needed to drill out NRV from one Primus No. 5 stove (1934). I made new thread with M8*0,75 tap. To turn NRV into that thread needed some force from the beginning. I made M8*0,75 thread to a piece of steel and I made sure that thread is perfect. To turn NRV into that thread also needed some force from the beginning. I took NRV out and saw that treads of it had deformed a little bit. So the threads were not exact match. Maybe thread angle in NRV is 55° or pitch was not exactly 0,75mm.

Maybe after you get thread done to the pump tube do a same thread to a piece of steel and turn NRV to that thread first. That would deform NRV thread to M8*0,75 and it's easier to get into the thread in pump tube. Also removal of NRV will be easier if it's needed some day because threads are having better match.

 

Thanks Afterburner, will do that, it is better to know from the start than to learn from the mistakes.