Non-rising/‘camming’ NRV tool

Discussion in 'Fettling Forum' started by presscall, Mar 7, 2020.

  1. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Ok, more of a technique for best utilising a good quality ‘basic’ NRV tool rather than the mechanical solution gone into in THIS post.

    This is the one I’ve used for years. Primus branded and although the tommy bar long since succumbed to robust handling ...

    A090DAAF-0C1D-4974-8983-E1110419760E.jpeg

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    ... the business-end has remained indestructible. Quality steel, hardened and tempered and precision machining.

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    So, my technique for using it.

    Clamped vertically in a small machine vice, gripped between my feet as I sit down to the task.

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    The test case was the NRV in the Sunflower Vacuum Oil Company stove featured in THIS post. A tough case, peering down the pump tube I could see a NRV head chewed by unsuccessful attempts to remove it by one or more previous owners.

    I engage the tool with the NRV and press down (firmly but not too heavily) on the fuel tank while turning the tank anti-clockwise.

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    The characteristic ‘crack’ as the thread bond breaks and the NRV unscrewed.

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    The tool hasn’t failed yet, even on worse examples than this one.

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    John
     
  2. redspeedster

    redspeedster United Kingdom Subscriber

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    I've sat on my hands through this whole NRV tool saga, but I need to comment.
    IMHO if the NRV won't come out with the standard tool, break out the torch. Because too much torque on the NRV and the tube it sits in isn't good.
    You can ruine a perfectly good stove or pump tube. Just unsolder the tthe tube and work from there.
     
  3. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @redspeedster
    Fair comment Gary, but although I don’t baulk at removing and re-installing a pump tube it’s always preferable to get the NRV out without that additional job.

    I’ve never ruined a tube or stove getting a NRV out, but my experience of a discouraging number of Burmos Stoves (mostly their 96 half-pinter though) is that end caps are very poorly soldered.

    It’s made me reach for the blowlamp and soldering kit before the NRV tool (almost) in those cases.

    John
     
  4. hikerduane

    hikerduane Subscriber

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    I've resorted to unsoldering a few pump tubes in my time, just not my forte, easier, quicker to remove a NRV if possible. Only pump tube which had a crack was a British 96 size stove. Bernie Dawg found the crack as I had issues fixing or removing the NRV. Not all have the skills or gumption to tackle much that is required to fix stoves.
    Duane
     
  5. Big Si

    Big Si Subscriber

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    In the past, when I needed I unsoldered the tube, cut the end of the NRV off as close to the tube as possible then drilled it out, with a drill smaller than the screwed part that the NRV sits in. Then re-solder the tube fit new NRV. Just my take on it, remember to clean up the joining surfaces well and use lots of Flux to get the solder to flow well. To get rid of any excess solder, warm it up (The solder) and brush or flick it off using a piece of leather. I use a piece of an old belt.

    Si
     
  6. hikerduane

    hikerduane Subscriber

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    You risk unsoldering the end of the pump tube that the NRV is screwed into, maybe a heat sink reduces that risk? I went round and round some years back with one, trying to get the piece centered and sealed.
    Duane
     
  7. Radler

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    @presscall

    I understand quite well, how proud you are, to have extracted such a deformed NRV. But I think your advice how to bring the most brutal force on the tool is not a good one. It will encourage people to ruin their stoves with heavy hands.

    It is very important to have the tool fixed exact in the long axis of the pump tube at both ends. If this is not the case, the slightest lateral movement will make the tool rising and deforming the NRV. I am sure you know this, your craftsmanship is excellent and proven in many posts here. Allow me to add the following advice.

    The simplest way to keep the tool centric is to wind paper strips around the shaft of the tool until the reel fills almost the diameter of the pump tube. This should be done first, before the NRV is ruined by previous attempts with the nude tool.

    Best Regards
    Radler
     
  8. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    That’s not what I was advocating Radler, just the best way to apply torque.

    I assure you and anyone who may read this NO STOVE WAS HARMED IN THE MAKING OF THIS POST!

    John
     
  9. hikerduane

    hikerduane Subscriber

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    I have yet to ruin a stove, many times it's close to all my strength to loosen a NRV. The biggest issue has been the tool rising off of the head and rounding it off. Just about all I have had to work on were for my over 50 Primus 96 stoves. What did not work was wedging the fount with a tool on the NRV in the jaws of my vise. That started caving in the area by the pump tube. Fortunately I have only had maybe one or two larger stoves with hard to extract NRV's.
    Duane
    PS: I don't think I have any super rare, classic stove that any work or repair to it should be by a expert.
     
  10. MrAlexxx SotM Winner

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    Interesting post and with good advice I wish had known. Nothing damaged here too seriously but if something isn't done right the first time you certainly do make more work for yourself later. I'm also glad that no stoves were harmed in the making of this post. lol :)

    Alex
     
  11. Tony Press

    Tony Press Australia Subscriber

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    John

    Your thread has reminded me that I have a few of those Swedish NRV tools in the shed.

    You have given me the motivation to make a modification to one of them...

    I usually do what you do (with the vise) for stubborn NRVs. But I’ve had to resort to de-soldering occasionally.

    Tony

    @presscall
     
  12. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Treasure trove.
     
  13. Afterburner

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    I agree first sentence. Rising can be prevented with a cap/nut screwed to pump's thread.

    [-X:lol:

    Simplest way to keep tool centric is to make tool to be centric. I made tool shaft to have 0.4 mm / 0.016" gap to pump tube and on locking down nut there is 0.1 mm / 0.0039" gap to shaft on 'bearing surface' : AB NRV-00/111 I think that on next version I reduce pump tube to shaft gap to 0.2 mm / 0.0078"
     
  14. afoton

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    Thank you. After several different atempts the last 2,5 years, today your technique got the nrv out of my Radius 43. Now I am a big leap nearer a working no43.
     
  15. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @afoton
    I’m glad it worked for you. I admire your perseverance, but a Radius 43 is certainly worth the effort!

    John