The one piece molded Optimus pip is no longer made so when it becomes necessary to replace it you will need to replace it with a conventional pip and brass pip holder. There are many Asian made valves on the market now that have a poorly made leading thread. There is a way to smooth it out so that it'll fit better that is described earlier in this post but so far I have been unable to do it successfully. I use them for parts instead. I open them up and take the brass pip holder and pip and use them in an Optimus valve. Ivar, this is only a problem with some of these Asian NRV's. I've had some that did fit OK. There are two types of NRV washer, lead and plastic, Lead was always used in the past but now there is an anti-lead movement and some people feel plastic is a better choice. I don't think the plastic will be a problem for you in the future. Ray
BD found that cleaning the leading threads 'should' fix the fit problem. The 10 I bought have more problems than just the threads. The flats will not allow a NRV tool to fit the head for inserting the NRV. @loco7stove Stu's fine tool does not work either. They are not square cut and the sizes vary quite a bit. The size varies from .198 - .2035 (inches). Burrs are left in several places that would block the flow, and also break off and block flow. I have not yet gotten around to making then right. But, they can be made right, it just takes some skill and patience. The burrs are easy to fix, the threads a bit more difficult, but the flats may require a bit more precision. A file may work with a steady hand. The future problem, I see, is that a bad set of flats may result in a damaged NRV head, during attempted removal, if the NRV gets tight, as we know they can. I just checked, and Fettlebox (@Spiritburner) does not have NRVs, so I assume that they have not secured a quality NRV as of yet. Ken in NC
Made in Sweden is "the best sign" on NRV to fit into Swedish stoves. The NRV with lead gasket is older made so it's threads fit PERFECTLY to old Swedish stoves. I would suspect that there is two versions of NRV with plastic gasket. Older version is like Swedish NRV with lead gasket((=same thread). Newer version is for current Optimus Nova, Nova+ and Hiker. That might be with different thread (M8*0,75 which is very-very close to original thread) but that is unconfirmed information. I can compare older&newer "Made in Sweden" NRV's with microscope to see if there is any difference on threads. You cannot know what you get before you see them. I would look for "Made in Sweden" NRV with lead gasket. That should be the best available NRV (for old Swedish stoves). I would guess that plastic washer is almost as good as lead gasket. Tightness of both would be good to check time to time.
@Spiritburner, I meant that the Fettlebox does not have NRVs for sale. I did see the refurbishing kit.
I continue to this thread about matter that was discussed also here: https://classiccampstoves.com/threads/primus-nrv-m8-thread.36786/#post-381559 Just for testing I made a die for re-treading poor quality NRV threads into M8*0,75 thread. I bought cheap M8*0,75 die and grinded 'lead in' off from one side of the die. With that side of the die it's possible to do thread down to lead gasket of the NRV. Other side can be used for start of the work since grinded side is not easy to get running into NRV thread it original thread is too poor. First turn die into 8mm round steel bar: Drill sharpening grinder is perfect for grinding off the 'lead in' from one side of the die since grinding angle can be adjusted and there is a chuck that can be rotated to get nice finish: Un-grinded side of the die with 'lead in': Grinded side of the die with zero 'lead in': That die works quite ok for re-threading the poor quality NRV thread. Somewhere I have a detached pump that I could use to test how well re-threaded NRV works. I need to find that pump to do final approval test for the modified die...
I have a strong idea that most if not all of these e-seller replacement stove parts are actually coming from Taiwan and are, at best, reverse engineered. The UK sellers (Julian and others) are only commercially inclined unlike Ross who also has the hobby as a passionate interest. Julian loses my faith as he is selling some fairly unworthy repro items and seems willing to hype up just about everything he has including those wretched thick brass domes which he flogs as pressure stove heater dome conversions by sitting on the pan ring. They are absolutely NOT intended for this and, I think, come from ex MOD Taylor cabin heaters made in the 1950's for, I think, the old British Rail as was. The Indian made burners are better than nothing but barely ! I have spent some of my working life sourcing engineered parts around the world and getting them copied and a lot of this with Asian Nations. India is the current source of aftermarket burners and they are a living hell to deal with on quality, fit and consistant production. I bought a few out of interest from Julian several years ago and they are horrendous. I even doubt if they are brazed together on a decent jig or if the threads are CNC cut. The x3 that I obtained were all decidedly lopsided and god knows what the actual melting qualities of the indian brazing wire are. I have inspected many Indian machining and assembly factories in India (mainly around Rajkot) and all they really are is a huge number of interdependant very small enterprises who often only undertake batch work on specific operations but never make the whole item ie one will cut the metal, another place will bend it, another will machine some parts and the last one will assemble and maybe another will pack for export etc etc...a bit like the Sheffield Little Mesters system of metalworking but without reliable skill levels and it always shows in the finished item. Some of the Indian factories are damn good and very skilled but for every one of these there are 50 that are not. Very old machinery, unskilled and illiterate staff, hand tool use where any place else the function would be via a machine etc etc. Its really more like a intertwined load of Cottage Industries and the only way to get decent quality out of them is to invest time there to show them and then pay people to check ongoing so they dont revert and I doubt the market for their products would make it worth doing anything other than phoning through orders and leaving everything else to the factory... I doubt if there is anybody in Europe making retrofit parts commercially and to a good EU standard ??? Mike
Hi Kerophile, I have read the linked article and its very true. The one thing I did really see in the Indian Factories was a great willingness to improve but very often with no realistic prospect of achieving it. They other thing to understand in context is that the majority of these enterprises were originally setup to provide for the home market where anything that works and is affordable is the standard as opposed to the export market with a much higher minimum set of criteria. Much of Indian manufacturing ability has its root in their need to keep British made products (cars, stationary engines, motorbikes, buses, trains etc etc) going post partition. The original Indian factory managers and engineering staff were the ones trained and setup by many British companies to run their Indian offshoots and joint ventures. These days India does a lot of sub contract machining for major Western manufacturers who view them as more friendly and reliable than China to deal with and with less prospect of having IP and Copyright abuse issues which plague China and which the Chinese Government simply ignore. Kind Regards, Mike
Dang, wished I’d read this thread a couple of days ago. On Monday I received a two-pack of NRVs from Julian. I needed to replace the valve in a 00 that broke apart when I was disassembling it. Not thinking I needed to inspect the new valve first, I just inserted it into the pump tube and gave it a go. The threads seemed to take up normally and take a firm seating. The stove ran great afterward, so I hope all is well, and the valve is one of the good ones. Basil
If NRV went in without extra effort maybe threads were ok. Those that we were discussing earlier on this thread were VERY difficult or impossible to screw into bottom of the pump.
