Hey all, I need to make a new pump tube and need to know the thread size of the standard nrv(opti 123, 8r). I assume it is a pipe thread but will need to buy a tap. I don't want (or need) to buy a whole set - just a single tap Thanks Dave
Hello Dave Good question! Just so I am clear. Your talking about the non return valve on pump caps right? The barrel/housing with outside threads that screw into the cap. I don't know the measurement but I will measure one at the shop once I get out there. Jeff
Hi I think he means the thread at the bottom of the pump tube where the NRV screws in , i don't have any idea what size that is by the way, could be a job for SUPER BERNIEDAWG MAN or THE PHANTOM KEROPHILE Best regards Stu PS it'd be nice to know myself
Ah I get yeah. This is why I asked. Opti 123, and 8r's don't have pump tubes. What stove do you need a tube for? Jeff
NRV thread size is not a pipe thread. It's a standard metric fine thread M8 X 0.75. Thread in another head of pump tube a place for a pump lid has a metric thread M16 x 0.75. Regards Hannu
Hi Hannu I was just wandering in from the shop after doing some measurements on this. I am afraid that I agree with super-precision machinist Doug Wiese (exeteryak) on the sizes of the NRV components. Here is a drawing he did of the NRV: https://classiccampstoves.com/posts/50534 The drawing is part of this thread here at CCS which may be found in the Fettlers Masterclass section: https://classiccampstoves.com/threads/5646 Both Doug and I measure the thread at 36tpi which is much closer to a metric 0.7 pitch. Here is a chart for threads that I find very helpful for this sort of work: http://mdmetric.com/tech/tict.htm Now, not to say that a M8x0.75 would not work in practice, but I suspect you'd succeed with that size only by deforming the brass threads slightly. Just a heads-up. I think a M8x0.7 would be a closer match to the actual thread, but perhaps just a tad sloppy. Probably still good enough. Let us hear how it turns out should you try it Dave. Cheers, Gary
Hi all, I've tried the M8 x 0,75 for cleaning up some damaged threads and found that it came close, but was not perfect. I would only use it in emergencies , like to 'rescue' an otherwise lost pumphousing, but certainly not when making new parts. Just my 2€cents! Regards, Wim
In this project I'd use a tap of M8X0.75 and it's works fine without any problems. I've made a complete pump tube unit myself. https://classiccampstoves.com/posts/18763 Hannu
You are right - sorry for the confusion. I am actually repairing an old Aladdin lantern that has a damaged pump tube and noticed there is enough metal (small enough hole) to re-tap it and use an NRV that I have from a 111 fuel tank.
