The second o-ring groove

[herbicide]

I hadn't really looked, before fitting replacement o-rings into said grooves, but it turns out that the second (that is, furthest out) o-ring groove on well... everything I have with one (solarforce bodies, FM 18650 extension, TnC E2C) is shallower than the inner one - which comes with an o-ring fitted.

I could see this being used to enhance water resistance - my reason for buying them, in fact (that and there was a gap that looked like it ought to be filled) - but why make it so shallow that you're not able to fit the head back on afterward?

Thoughts? Do you share my frustration? Have I got it all wrong?

Footnote - remove the anodising from the flat of the tailcap end on your newly arrived FM extension before fitting it, as frustration (and blisters) ensue otherwise.

 

[Kestrel]

I use all the second grooves in the tail ends for a second o-ring, but the bezel end, yes I found that to be an issue. A while back I went around and around to try to find a narrow enough o-ring to fill those shallow second grooves on the head end, I did end up finding some very narrow ones, but they still weren't slim enough to fit. :shrug:

 

[abarth_1200]

Maybe the 2nd shallower groove is to aid in the compression of the o-ring to increase water resistance, ask surefire and see what thet say, they might even send you a free o-ring to try it out.

 

[Benson]

Sometimes what looks like a second O-ring groove may only be intended as relief for threading. In these cases, while you may be able to fit a second O-ring in, it is likely to get chewed up in short order by the threads (especially if you don't keep it well lubed!), and of course the depth may be inconvenient for standard sized O-rings. One option is to try a smaller diameter O-ring -- the extra stretch will thin it somewhat.

 

[herbicide]

Sometimes what looks like a second O-ring groove may only be intended as relief for threading.

I hadn't thought of that, but I can only find it on SF P-series (compatible) parts. E-series bodies don't have any space between the thread and the o-ring at all.

 

[abarth_1200]

Usually the second o-ring groove is furthest from the thread, In my 6P the groove with the o-ring in it is the one closest to the threads and thats the way it came from new, I have however seen the small groove between the o-ring groove and threads on other lights

 

[bstrickler]

There's actually a CPF member that will fix that groove, so you can put an o-ring in there. I can't remember his name off the top of my head, but give me a few minutes, and I'll find it.

I was going to have him to that to my 2 6P's, because I'm anal about water-proofing stuff (even though I don't really expose my lights to water), but never got around to it.

Edit: Found him.

Tekno_Cowboy

Just let him know what you are wanting done, and he should be able to hook you up for a fair price.

~Brian

 

[Linger]

if you take a look at ElectronGuru's SF->18650 boring thread there's a set of pics re: installing the 2nd o-ring.

 

[ElectronGuru]

In my 6P the groove with the o-ring in it is the one closest to the threads and thats the way it came from new, I have however seen the small groove between the o-ring groove and threads on other lights

if you take a look at ElectronGuru's SF->18650 boring thread there's a set of pics re: installing the 2nd o-ring.

Here's the image in question. The first/factory ring should be installed in the slot, furthest from the threads:

BTW, I've seen some factory lights (9Ps) where the second ring is the same size (ala lighthound) and some factory lights (M2s) where the second ring is smaller, stretching out thinner. The first works as well, with plenty of lube and provided the inside of the tailcap is smooth.

 

[kelmo]

I use GITD O-rings for the second grooves. Chances are you will be changing things in the dark with your backup light. So the glowing ring will help guide you in the dark or locate things you set down. On the bezel end they tend to make alignment of the threads a practice in patience so you don't cross thread your light.

 

[Kestrel]

but why make it so shallow that you're not able to fit the head back on afterward?

What I think the OP is saying in Post # 1 is that his difficulty is in getting the head back on, therefore he is talking about the shallow groove in the head end. I don't understand the discussion about the tail ends, it sounds like there isn't as much of an issue on that end? :thinking:

A clarification by the OP would be helpful, he cited both tail and head o-rings with hyperlinks in his post #1, but it isn't completely clear to me as to which end is providing the most difficulty in his aftermarket bodies.

I know my SureFire 6P, C3, & G2 bodies have no issues with a second o-ring in the tail end (my G3 being an exception to that), but the second groove in the head end for each of them poses a significant problem - I have not been able to find an o-ring to fit that shallower groove.

 

[herbicide]

What I think the OP is saying in Post # 1 is that his difficulty is in getting the head back on, therefore he is talking about the shallow groove in the head end. I don't understand the discussion about the tail ends, it sounds like there isn't as much of an issue on that end? :thinking:

A clarification by the OP would be helpful, he cited both tail and head o-rings with hyperlinks in his post #1, but it isn't completely clear to me as to which end is providing the most difficulty in his aftermarket bodies.

Er, yes, I could have been clearer, sorry. The trouble is with the head end - the head won't physically fit over the outer o-ring.

 

[Moddoo]

Any time that a thread is cut into a part, a thread relief is cut where the threads end.

This is the groove that you are trying to fit an o-ring to.

It is too small for any standard o-ring.

Surefire lights are completely WATERPROOF to 33ft.
I have tested this to be true.

IMO, there is no reason to try to fit an o-ring to the thread relief groove in the head of your light.

Have you had a problem with water getting into the light?

I have no solarforce lights to test waterproofness.

 

[herbicide]

I haven't even submerged it, but it'll probably be as waterproof as a Surefire *P.

 

[anonymoususer]

Any time that a thread is cut into a part, a thread relief is cut where the threads end.

This is the groove that you are trying to fit an o-ring to.

It is too small for any standard o-ring.

Surefire lights are completely WATERPROOF to 33ft.
I have tested this to be true.

IMO, there is no reason to try to fit an o-ring to the thread relief groove in the head of your light.

Have you had a problem with water getting into the light?

I have no solarforce lights to test waterproofness.

I assume it wouldn't be very difficult to machine the groove to accept another o-ring, correct? You folks offer a second o-ring for the thread cut relief on the tail end.

After that i would assume the next weak spot would be the lens seal or the switch. Any CPF'ers have any suggestions on how to improve that seal?

 

[carrot]

IIRC, M-series Surefires use a double o-ring on the tailcap for water resistance when being used underwater.