Damaged NRV

Jim Easton · 26 Mar 2026

Hi. I have damaged the NRV on my Primus stove. Has anyone drilled this out without damaging the threads on the mounting base. If so what size of drill did they use. I have not got a replacement NRV yet for comparison.
Thanks,
Jim

Rangie · 26 Mar 2026

Its a lottery...
But genuinely, try the search function, there have been lots of threads over the years, everything from drill & screw extractor to complete pump tube removal to access it.

Alec.

Jim Easton · 26 Mar 2026

Thanks Rangie. Had a quick search on the forum but apart from removing the pump tube didn’t see much. Do you know how I can prevent solder spreading if I go along that line.
Cheers,
Jim

kerophile · 26 Mar 2026

Pump Tube Removal and NRV Rework

Messy solder: Worth a retry?

ROBBO55 · 26 Mar 2026

An unfortunate circumstance: Optimus NRV

Stuck Rounded NRV

kerophile skrev: ↑

Hi @jean francois lutz Classic Primus stoves were first introduced at the end of the 19 Century before standard thread forms were developed,

Other Manufacturers tended to adopt the same thread form as the early makers to make spare parts compatible and to be able to compete in the valuable spare part market. Special thead forms also made copying difficult for small-scale operators.

Sometimes a modern thread form can be an “almost” fit; but that is chance

Have a look at this post on NRV Thread size:

From this long thread:

Warning NRV

Best Regards
Kerophile.
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ROBBO55 · 26 Mar 2026

Afterburner skrev: ↑

I did research for NRV's but forgot to post results...

I used a microscope that has 60º angle screen inside the ocular and table has X-Y moving capability and knobs to move the table. X-Y moving knobs are having micrometer scale. (Something like this http://www.ebay.com/itm/Used-Nikon-MM-11B-Measurement-Microscope-/400294190330 but table moving knobs are like mega size micrometer vernier knobs)

I have two adapters to mount DSLR into microscope but both of them were different size than in microscope. I haven't had time to make adapter ring so no photos from the measurements.

I had original Primus(stamped on NRV) NRV from un-used and un-opened Swedish Defence surplus Optimus 200 lantern spare kit. So that NRV should be perfect NRV to be a reference. With microscope and it's X-Y table I got results:

-thread angle 60º
-thread shape perfect triangles on outer and inner sides of thread
-pitch 0,73 mm
-outer diameter 8 mm

NRV's that are pictured in this thread: NRVs - Free plus postage

-thread angle 60º
-thread shape non perfect triangles on outer side of thread
-thread shape non perfect triangles on inner side of thread
-pitch 0,70 mm
-outer diameter 8 mm

NRV's that I received from Juliands:

-thread angle 60º
-thread shape perfect triangles on outer sides of thread
-non perfect triangles on inner sides of thread
-pitch 0,75 mm
-outer diameter 8 mm

(Both later NRV's thread triangles are missing the sharp tip. Tip of the triangle is cut about 20-25 % lower position that sharp tip would be)

Juliands NRV's work some how. 0,02 mm difference in pitch is not a big problem. When thread shape is not perfect NRV is difficult to screw in. If both sides of the thread are having un-perfect thread profile NRV is quite impossible to screw in.

I plan to try to make new thread onto those NRV's with M8x0,75 die to see it they work after that more better.

(Sorry for late return into this matter and for poor documentary without photos. Hopefully some one understands what I tried to explain... 8-[ )
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Warning NRV

Tony Press · 27 Mar 2026

Tony Press skrev: ↑

@swedmiro

I use a similar technique to @boknasild.

I've once successfully removed a ruined NRV using a drill with an extractor (left hand thread) fitted - but if you go down this path be very careful not to damage the threads that the NRV screws into.

Cheers

Tony
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Jack Tar · 31 Mar 2026

How to remove stuck NRV when the NRV head is damaged.

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Damaged NRV

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