NDI - tight head o-ring, help?

After cleaning up and lubing the threads on the Defender Infinity, the head became quite tight after sitting a little. Has this happened to anyone?

I used a little "Super Lube" which is a synthetic lube with teflon. The threads are all great now, but the head o-ring, and only the head o-ring has become rather tight. The tailcap is smooooth as it ever was.

I cleaned off the extra lube from both the body side and head side, and it was all buttery smooth and easy to turn again, but only for a few minutes. When I went to demonstrate the light to my dad (it's his now Happy Birthday! ) it was all rather tight again. It's tighter now than when it was new with dry squeaky threads. What happened, and why only the head? It makes changing brightness and modes tricky now. :sigh:

Yeah that happens to mine too, and I remember reading a few posts about this issue. I think the o-ring gets a bit twisted up. I find if I unscrew the head enough so that the o-ring is exposed and then screw it back on again it's nice and loose for a brief period.

The solution most people use is to put on a smaller/thinner o-ring. One of my spare JetBeam Jet-I O-rings worked perfectly. Except I don't know if that negates it's IPX-8 (whatever that means) water proof rating.

I ditched the o-ring completely. Even without it the light should resist casual spraying or extremely brief dunking (which is all mine is likely to ever have to endure), and the head is much more pleasant to use without it. You can actually feel the exact point where it comes into full power mode, and operation is much easier. It's also much easier to operate it one-handed, although I never do that.

I might eventually try other o-rings, but for now I'm happy without.

If you have a P2D, toss one of its spare rings on there, they work great.

The original oring twists and binds... Apparently it's okay for *some* people but many have problems.

Thanks for the suggestions.. I just remembered there are some extras included as well. I wonder if any of those will happen to be better, due to tolerances. If not, I guess I'll fish around the parts bin for some o-rings.

I had the same problem initially and solved it with a Fenix P2D spare o-ring.

The problem with the original one appears to be caused by the material the o-ring is made of that is too sticky. Besides it is not difficult to find o-rings in hardware stores. If you have other flashlights of similar size try out their spare ones.

I never tried any of the replacement orings in the package, but I have a feeling what might happen...

My tailcap oring seems fine, but I think what happens is it never get used, except a rare occation when I'll lock out the switch.

Where the head gets turned a lot.. I suspect this seems to 'damage' this soft oring.

I'm going to pick up a big box of orings from Harbor Freight sometime.. if I do, I'll try to identify the exact one to replace the NDI so it's easy to find. So far I've never had any luck, all I find in the regular hardware stores in plumbing are too big or too small.

Try sanding the oring a bit,put it on a 1/2 socket,and chuck it in a drill,slowly rotate with light sand paper,go slow,you cant put more back on once sanded.This work great for me.

Paul6ppca said:

Try sanding the oring a bit,put it on a 1/2 socket,and chuck it in a drill,slowly rotate with light sand paper,go slow,you cant put more back on once sanded.This work great for me.

Click to expand...

+1 I did similar with my dremel and it is very nice now.