I know some have no idea or think it is simple to concoct one in 30 minutes, a cheap NRV tool that can be locked down into place, so when force is applied to unscrew a very stubborn NRV, it won't ride off of the NRV or round the head. For me, the two issues are making a close to precise slot to engage the NRV head and getting the upper part of the tool shaft to take the torque required to "snap" the NRV loose, since if using a drilled out spare pump tube cap, makes trimming down the tool shaft enough so that there is still some material left on it to not twist and break after all the work. I've seen a few examples, one was very nice and robust, saw one made from a hardened steel bolt with a round chunk of steel brazed on the end with a slot cut in it, but that would need the upper portion trimmed down so some sort of cap could go over the shaft and screw onto the pump tube, with some flats cut into it to allow a spanner to engage it or a adjustable wrench. Anyone up to the task yet? Has been years that some of us have been wanting something. Sorry if you have no idea of issues with NRV's, I have a large collection of Primus 96 stoves and it pains me to have to resort to unsoldering a pump tube to access the NRV. Duane
@hikerduane What has worked consistently well for me for years now is a Primus-branded NRV removal tool held vertically in a vice and I turn the fuel tank on that. Contributing to the effectiveness is that the Primus tool is a precision fit and the ‘slot’ is NRV head-shaped, so once it’s engaged with the NRV there’s no sideways movement or ‘camming-out’. The metallurgy of the tool is excellent too, high-carbon steel properly hardened and tempered, so it’s never degraded. Turning the tank on the fixed tool enables me to better judge and maintain downward pressure and apply sufficient torque. If the NRV head has been moderately mangled by a previous owner the technique still works. Too mangled, out comes the pump. I know that doesn’t address the ‘non-rising tool’ (!!!) Duane but though lower tech it’s a work-around that’s not made me hanker for something better. John
I have a good selection of tools, one or the other usually work. The Primus 96's have the most issues as they don't have a lead washer under the top piece. I've done what you mention, the tool still slipping or rising off. I've dented a couple trying to wedge between the ends of a vise. Some are quite stuck. Duane
Sorry, not yet up to the task... I have been thinking to make that kind of NRV tool for couple of years. I have machines and recently got a workshop for them. Now I am putting machines into working condition but it will take some time to get them all into running condition. Lathes are almost ok... I am working with collet draw bars and small chuck draw bars. Once they are ok lathes are done. Milling machine(old and used) that I bough needs a full clean out and service. Also I need to learn to use it. Never used one before. Cutter grinder is ok, but I need to make work piece holders for it and modify work piece holders that I have for other brand cutter grinder. Also this kind of machine I have never used before. I have been thinking about NRV tool set that would have one twisting handle that would fit into various size 'NRV sockets' for different size pump tubes and NRVs. Maybe I first need to make one test piece for #5 size to see how planned concept would work. Locking down for different size pump tubes & NRV and fitting into common twisting handle is a bit challenge to do, but maybe there is some solution for it.
Here is a link to a post of the design and construction of a clever and relatively “simple” NRV removal tool: Making a special key for NRV removal Best Regards, Kerophile.
If you know that there is not a lead washer, then penetrating oil should work a lot better. The washer has appeared to be an inhibitor to the penetrating of the penetrating oil.
Unfortunately this beautifully made tool seems to no longer be available. Although not the lock down type, it has not failed me yet. However, I have no 96 stoves to test it on.
I'm thinking this isn't much of an issue for people as they may only have a stove here and there of many different sizes, brands. I have a number of different types of tools, even a couple of Stu's early models that I have mostly used. 20% of my collection are Primus 96 stoves, so I have a need and have had many that had a stubborn NRV. No new news. Duane
@hikerduane Just to recap for any machinists willing to take up your challenge Duane, the relevant tool is Primus part number 1596 (from a 1937 Finnish catalogue, Stove Reference Library HERE.) The collar on the shaft will be fixed at a position where when the head of the tool is engaged with the NRV and the pump cap is screwed down the collar butts up to the underside of the cap, preventing the ‘business end’ from lifting off the NRV head. Not a ‘universal’ tool, there’d have to be a version for varying stove bores and lengths. As I said earlier in this thread, the slender proportions of Primus NRV tools require quality high-carbon steel, suitably hardened and tempered, in order not to snap, or corkscrew, or have the tool head degrade after a few tussles with NRV’s. John
The slender shaft has concerned me too. That tool is real simple. Messed with pieces yesterday, may ask at the parts houses in town for help, they don't act real helpful for a small sale. Duane
It is not going to be easy to find people interested in this hobby. And less so with the enthusiasm that you have Duane. Ken
@JP2, I"ve seen similar online using a long, threaded bolt, but may not find one threaded the whole way, could then just notch the head to accept the NRV head without adding a pipe sleeve, would still be centered. But that would be a weak point I have found out, tried to thread a nut over the cut but that wasn't working. I can see in the link that the double nutted, reinforced rod where the bar passes thru strengthens that area and eliminates making flats to engage a wrench. Duane
@hikerduane Ok, what I like about this technique is that the modified nut at the bottom of the pump is push down and hold the rod tight on the NRV when you unscrew it. Only the rod do the job. Also your don't scratch the wall tube.
Not sure, but I think that won't work on the slender pump tube on my 96's, the nut at the bottom has to be ground too much and the NRV head requires a wider slot. I may try making a slot in threaded stock and sliding a piece of pipe over it. I saw one online that had a round chunk of metal on the end of a bolt or threaded rod with a slot side to side, the metal keeping the tool centered. Duane
Duane, just scale everything down to make a separate NRV removal tool for your 96s. The design is exactly the same. My regular (dirty) 2 pint removal tool is on the left, and the one for 96s on the right. In the latter case I didn't grind down a nut, I fitted a tight steel sleeve over the threads after cutting the NRV slot. Then I crimped it in place with mole grips. From memory the 96 tool is made from 7/16" threaded bar.