# DIY: Surefire G2 nitrolon bored for 18650



## KQL (Jul 10, 2014)

I've seen posts on how a nitrolon Surefire G2 can't be bored like the aluminum cousins 6p and 9p because of the metal sleeve used in the G2. After looking at the light, I didn't see any reason why it can't be bored, as long as the sleeve is retained and expanded. I took some photos along the way. I am by no means an expert at this and there may very well be better ways to do this, I was just curious and used what I had around the house. Don't try this at home, it was just for fun. It took me ~6 hours, just buy a bored 6p and save yourself the trouble. I am not able to post attachments, so these photos are hosted on my site. Click on them to get a larger version for a closer look.


I used common hacksaw to cut through the sleeve inside the light. Take the saw off, feed through the body of the light. I wrapped the light in painters tape so I can clamp it down lightly.







Start cutting the sleeve from the inside. I found that with my sloppy technique, the ends were cut first, so I took it slow and tried to cut evenly, only through the metal sleeve.







Once the sleeve is cut, it is easy to remove with a pair of needle nose pliers. It is just press-fit into the body, there was no adhesive of any kind. We need to save the sleeve, so be careful and take it out. Note that there are 2 different lips on the tail and head ends of the sleeve.







I obviously did a poor job here and cut into the body, but we're going to bore that part out, so no harm done.




The 18650 will be riding inside this sleeve, so I used a file to take off the rough edges in the cut and used 220 grit sandpaper to make the inside edge of the cut very smooth and dull, so as not to cut through the insulation on the 18650.







Then I used a trick I saw on youtube where someone was boring a 6p. I built up a duct tape plug on my 1/2 inch drill bit and then taped 80 grit paper to it. Using the drill I was able to quickly bore out the body to match my 18650, an EagTac 3400mAh. Because I could not use the battery for fit, since the metal sleeve will have to go back it, I built up a 1mm sleeve on the battery with painters tape to account for the 0.5mm thick metal sleeve, plus a little extra for an easy fit. I found here that sanding too quickly will get the G2 body hot and will melt gobs of plastic to the sandpaper, so take it slow. Let the body cool if you feel it getting hot to the touch.










The O-ring grooves got pretty thin after this process.




Once the inside diameter of the body has been sufficiently enlarged, I flexed the metal sleeve open a bit, introducing ~5mm gap. I tried very hard to keep the cylindrical shape of the sleeve and worked slowly with my hands. I was counting on the spring-like nature of the sleeve to help me here. I expanded it to a larger diameter than the ID of the body, then gently squeezed it an fed it back into the body. It tried to expand back to its larger diameter, thus assuming the new diameter of the body. Two issues are apparent here, at the tail end, the lip in the sleeve is now too large and will catch on the tail cap threads. But also the bezel end of the sleeve had an inside groove for the top lip to rest in, which has now been sanded away.
Tail end:




Head end (you can just barely see the lip and that it's not allowing the sleeve to lay properly):




To fix the tail end, I took the sleeve back out and just used the file and 220 grit paper to reduce the lip to where it was even with the outer diameter of the threads on the body. For the front lip, I used a thin sharpie to mark how far the sleeve comes toward the head.




And then used a dremel to introduce a shallow channel for this lip to rest in. This end of the sleeve rests in a pretty thick part of the body, so no danger here of cutting too deep, but I still kept it shallow.







Once the sleeve slipped into this groove, it was ready for the 18650.










And here she is. I don't have a 3.7V bulb, so this is just the stock P60, which I was pleasantly surprised can be powered by the 4.2V freshly charged 18650.




The electrical tape on the head is for my diffuser, not part of this mod.

Hope you've enjoyed my little project.


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## netprince (Jul 10, 2014)

*Re: DYI: Surefire G2 nitrolon bored for 18650*

Nice mod. I like it.


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## ElectronGuru (Jul 10, 2014)

*Re: DYI: Surefire G2 nitrolon bored for 18650*

Fun mod, thanks for sharing!


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## m4a1usr (Jul 10, 2014)

*Re: DYI: Surefire G2 nitrolon bored for 18650*

:twothumbs Now that's thinking outside of the box. Destined to be an inspiration for others! Good Job KQL


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## Conte (Jul 10, 2014)

*Re: DYI: Surefire G2 nitrolon bored for 18650*

Nice mod. 

I wonder if the tail end will be a weak link now where the O rings sit.


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## m4a1usr (Jul 10, 2014)

*Re: DYI: Surefire G2 nitrolon bored for 18650*



Conte said:


> Nice mod.
> 
> I wonder if the tail end will be a weak link now where the O rings sit.



Strong possibility if dropped or the twisty is tightened excessively over a long time period but the fix is sooooooo easy. Since it has the metal liner just take it back out and apply some 5 min epoxy to the inside of the body, then reinstall the liner and insert something to expand the liner so that the battery slides in and out with no resistance. I bet it would last many, many years of normal flashlight abuse. I like this mod the more and more I look at it. Except that I would use a 18650 Vap body for those smokeless cigs. They are thin walled and combined with what KQL came up with I bet we see 18650 powered Nitrolon Surefires being out there.


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## Conte (Jul 10, 2014)

*Re: DYI: Surefire G2 nitrolon bored for 18650*

Yeah, that's what I was thinking too. 
I would be tempted to reinforce it. Maybe fill in the Oring slots and put the ring somewhere else. 

Mind you, I bet that liner would keep that section rigid enough that it never breaks. It'll depend on how much the metal flexes and how brittle the poly is. 

I have an off brand poly host I might be tempted to try this with. A "Noma" 6v host. 
It would actually be easier to work with since the liner just slips out. 



m4a1usr said:


> Strong possibility if dropped or the twisty is tightened excessively over a long time period but the fix is sooooooo easy. Since it has the metal liner just take it back out and apply some 5 min epoxy to the inside of the body, then reinstall the liner and insert something to expand the liner so that the battery slides in and out with no resistance. I bet it would last many, many years of normal flashlight abuse.


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## KQL (Jul 10, 2014)

*Re: DYI: Surefire G2 nitrolon bored for 18650*

For sure the left over material in the tail section is very thin. It's more like a membrane almost. When I was sliding the metal sleeve back in, I could see the contours of the bezel-end lip as it went past those grooves. I think I'll be taking the head off to change the battery, best to leave that tail end alone. My battery slides in and out with no resistance, so I may have over-bored it. It took me a while to realize that the battery was not going in initially because the bezel-end lip of the sleeve was preventing the sleeve from laying flat in the tube. So I kept boring it out with the sand paper, and probably over did it.


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## Redhat703 (Jul 10, 2014)

*Re: DYI: Surefire G2 nitrolon bored for 18650*

Great mod. Thanks for sharing!


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## Kestrel (Jul 11, 2014)

*Re: DYI: Surefire G2 nitrolon bored for 18650*

Very nice. Folks have been asking about this for years, nice to see someone pull it off. :thumbsup:


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## tobrien (Jul 13, 2014)

good work!


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## BC FLASHLIGHT (Aug 20, 2014)

I agree! Good work. I have an old Surefire G2 and now that I have a couple TRUE Powerful LED Flashlights, I seriously need to get my G2 up to speed in the LED world. My incandescentnt G2 eats CR123 batteries, isn'tnt very bright and no longer meets my needs. I dont want to toss it aside but,,, I need some recommendations on the best LOW COST LED drop in module but what quality products that I should purchase.Here are a couple of things that I an thinking about doing:Finding a quality (reasonable cost) LED drop in that fit and give the most (REALISTIC) lumins.Modding the flashlight body to accept an 18650 rechageable battery. I have the ability to carry out this mod. Please give me your opinions on how this 18650 mod performs with a LED Drop in bulb assembly and what low cost LED drop in works. Ive seen them as low as $5.00 from off shore. What works and what is garbage.Is the multi mode LED drop in worth it?Thank youBill


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## Timothybil (Aug 21, 2014)

Well, there is always Malkoff, but they are not necessarily all that cheap (and with the quality product they provide no one expects them to be). Lumens Factory sells a D26 (P60 size) drop-in in either single mode or tri-mode for $28 USD. It uses a Cree XP-G2 at 350 lumens, and the tri-mode breaks at 5/30/100%. That is the module I have in my Seraph 6, and I really like it. And Mark at Lumens Factory is a well-know friend of CPF that always provides a quality product and great service, just like Gene.


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## hacklordsniper (Aug 23, 2014)

That is a quite inovative boring process without lathe, nice job.


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## RIX TUX (Aug 7, 2015)

nice job on that, I always liked the nitrolin better than the 6p, I use the 16650 battery in mine, it is not as powerful as a 18650 but works fine


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## etc (Aug 17, 2015)

Neat.

Question. I have 17670 Sony cells that *almost* fit into my G2x - they slide but are on the tight side, I got one partially in. however it looks they won't ever come out due to the super tight fit. 

Can you bore the metal sleeve without taking it out, removing maybe 1/4 millimeter or less? Seems I need just a tiny margin of space to enable 17650 to go in and out. Not to the point of 18mm or anything that big.

How think is the metal sleeve,did you get a chance to estimate when you took it out? i have a boatload of 17670 cells.


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