I published here, six years ago, a self-made NRV-tool. I am still using it with pleasure and never had problems since with stubborn pump valves. Today I present a simple way, how to make a better tool out of a standard NRV tool. Maybe this will encourage some stovies who need a non-slip tool. You need a hacksaw, file, vice and a standard NRV-key, 5.5mm socket, Allen key 5,5mm (7/32") and some washers for M6 (diameter 12.5mm). 1. Insert the NRV-key into the pump and make sure, it is correct on the valve. 2. Mark the end of the pump-tube on the shaft (red tape). 3. Mark the length of your socket on the shaft (white tape). 4. Mark the cutting line, 5-7mm from the white tape (where the yellow pencil points to). Cut the NRV-tool there. 5. The tool together with the socket will be about 5-7mm shorter than the pump tube. This is necessary to leave space for the rim on the inside of most pump-lids and to make the tool usable for slightly different stoves. The gap will be filled with shims (washers). 6. To file the four flats for the socket, you can use a disc grinder or a file. For indexing the flats, make a quadratic cardboard with a round hole and glue it on the tool. 7. Filing is done in many steps. Make 10 strokes for one flat, rotate 90° and make 10 strokes for the next flat, rotate 90° for next flat, file 10 strokes, rotate, file 10 strokes, rotate, file and so on, round and round, until the socket fits. If you ask somebody who has disc grinder, maybe he will help you. 8. Maybe the result of your filing/grinding work will not be very precise. You could use a epoxy two-component-adhesive (Araldite, UHUplus, etc.) to fix the socket permanently on the square. Check exactly the straight position! 9. A bit of a (lilo bellows) hose on the NRV tool helps to guide it on the valve. 10. How to use: The key with socket is set onto the NRV. Some washers fill the gap between socket and inner end of the pump-lid when the lid is screwed on the pump. Most pumps have almost the same length, but not exactly. The number of washers may vary from one pump to another. Screwing on the lid. The tool should now be fixed in its position. Then release the pump-lid ¼ turn to give space to the the NRV to move. Now you are ready to turn the key. Good luck! Radler If you are surprised, how easy stubborn NRV's are getting free with this tool, it's no wonder! It's just physics! When you use a common NRV-tool, you apply a lot of force to keep the tool down. In despair you may wish to have a helpful elephant at hand..... But this would not help, because
I made a similar one after reading your original post, and they work extremely well. Thank you for the clearly explained update which should be very useful to many of us, as NRV removal is an often recurring topic.
the carefull use of a percussion screwdriver solved the problem for me, put in tension the inpart driver and use a small hammer.
I bought a NRV removal tool off eBay that was made in Taiwan and cost £40 + £15 postage. I used for the first time last weekend and it worked perfectly. I had soaked the NRV in penetrating oil for 24 hours and filled the body with acetone and given it 3 x 30 minutes treatment at 60 degrees C in my ultrasonic cleaner. The tool was upside down in a vice with a block of wood underneath. I pressed the Primus 210 down with the NRV well seated in the turn, then used moderate pressure to turn the Primus stove body anticlockwise. It came undone with an audible click.
^^^^^ Any of the older stoves and lamps that have original metal-to-metal sealing at the bottom of the pump tube and have never been fettled can be extremely difficult. These are the seals that give a distinctive "click" when the seal breaks. Cheers Tony
