Surefire C-body maximum bore threshold?

[yazkaz]

I just achieved my very first bore tasks. Recently sent two 6P bodies to my local precision parts/machining facility for 18mm boring. Have asked the tech to stick to ~18.7mm (also Fivemega's standard bore spec) as discussed during our last meetup some months back (they told me the minimum tube thickness would be around 0.5mm which should be still safe to use on everyday basis without accidental drop etc.). The bodies came back to be in excellent condition and the bore is indeed tightly controlled at the 18.7mm range (eg. 18.69mm).

I foresee myself sending more 6P bodies for such process soon. Now my question is, should I go further and look into 18.9mm boring instead, for more protected 18650 compatibility? Will that be more risky and more prone to failure (or mishaps) during the machining process? And will that further weaken the body's tailside threads to a more dangerous level? And will a 18.9mm bore increase resale value (of the body concerned)?

Feedback appreciated......

 

[id30209]

Just stay with 18.7mm. Fenix batteries are one of the smaller and they fit okin even narrower bored body. Aw if you can find is also good option

 

[knucklegary]

I am having great success running Sanyo UR 16650 ZTA, 2500mah. The Sanyo fit stock bores with room to breathe, and supply sufficient power.
IMO leaving SF bodies intact makes them more valuable than modified.
The 18mm bore sizes leave a paper thin area around the tail cap oring groove. And, as you mentioned, are prone to breakage. If not from accidental drops, just from repeated tightening tailcaps loading batteries they can over time snap off.

 

[thermal guy]

I also run 16650/2500 in all my 2 cell surefires.The difference in runtimes against 18650/3500 is not as big as you would think and thinning the walls always made me Cringe.

 

[yazkaz]

I am having great success running Sanyo UR 16650 ZTA, 2500mah. The Sanyo fit stock bores with room to breathe, and supply sufficient power.
IMO leaving SF bodies intact makes them more valuable than modified.
The 18mm bore sizes leave a paper thin area around the tail cap oring groove. And, as you mentioned, are prone to breakage. If not from accidental drops, just from repeated tightening tailcaps loading batteries they can over time snap off.

I too have the said Sanyo 16650 under the guise of protected Keepower brand variants. Problem with these cells however is that they top off at 4.35V which means to achieve a full charge capacity you'll need a compatible charger (eg. Xtar VP2, Opus 3100/3400). Otherwise, the cell's capacity will be capped at around 2000mAh when topped off at 4.2V.

Kind of disagree with the second point -- it really depends on specific application. With the 6P body, a 18mm bore convert actually increases resale value (can go up to three times the original value). The same however cannot be said on other body tubes though, so you're correct about keeping those other bodies in stock bore condition.

BTW the tail o-ring groove area is where I refer to as having the minimum tube thickness.

 

[knucklegary]

The only issue I have with the 16650 protected version is they are a bit too long in my SF bodies.

 

[archimedes]

For me, between availability of stock (non-SF but compatible) "18mm" hosts and now a variety of "16mm" cells, I don't personally have any need of bored SureFire hosts.

Thinning metal generally weakens it, so in my mind, that decreases one of the best attributes of the (now discontinued) SureFires.

I realize that there is continued demand for bored SureFire tubes by some, but (again for me personally, at this point in time) any boring would reduce my interest in these items.

The more aggressive bore jobs would make me nervous, having seen threads shear clean off of some of these :shrug:

I consider flashlights to be tools and, although I am careful, tools do get dropped occasionally when used.

 

[lion504]

OR used to offer custom SF boring to 18.65mm. I wonder if they ever had a body fail. I have several bored 6Ps and they are holding up great. Mine were bored by bugsy.

 

[yazkaz]

OR used to offer custom SF boring to 18.65mm. I wonder if they ever had a body fail. I have several bored 6Ps and they are holding up great. Mine were bored by bugsy.

I've been told that, when dealing with such custom boring, there's a good chance of failure during the machining process in the long run. In other words, success on the first few bodies does not guarantee the same on subsequent ones. So care has to be taken at all all times (and in all aspects) throughout the process.

The other thing is user discretion. Knowing that the tail neck has become weak the user will need to to ensure no drop damage is induced upon the tail side, and that tailcap installation is not done with extreme force (torque). The latter seems to be easily neglected by many, including myself, as I sometimes do install extenders to bored 6P bodies along with o-rings that give me very tight fit.

 

[yazkaz]

Fenix batteries are one of the smaller and they fit ok in even narrower bored body. Aw if you can find is also good option

Not quite true. For the Fenix protected 3500 for example, a bore diameter of at least 18.8mm is required for effective fitment.
With the 18.7mm bore the said cell cannot slide in completely, only partially.
Also any 18650 with not so good external wrapping will not fit. Say, if the wrapping around the negative PCB bulges out by even a bit, the cell won't slide in completely.

Meanwhile the AWs have been a benchmark for 18mm boring. Fivemega even stated that his standard bored bodies (up to ~18.75mm) would fit the AW 3400 without issue, even though he does offer >18.75mm boring by special request.
For my offering of bored 6P bodies I closely follow FM's routine.

 

[Kestrel]

I've followed this thread with some interest, but refrained from posting until now.
My interests are maximum strength, but like others have also certainly enjoyed the 18650 capacity revolution.

I would have titled the thread, C-body /minimum/ bore threshold lol; I certainly don't want to loose material so as to be able to contain /any/ 18650 - I'm completely fine with leaving out the larger cells.

Thinking to my bored SF's, I happen to have the following:

• C2 bored by Moddoo/OR - minimum diameter :thumbsup:
• 7Z bored by PrecisionWorks - near-minimum ? :thumbsup:
• 6Z bored by Bugsy - maximum diameter
• C3 bored by a local machinist - over-maximum.

I have no regret with the very few 18650's that cannot fit into my smallest bores - in fact, I am quite happy that I have maximum material available, while only having the tiniest inconvenience by a couple of oversize cells not fitting - totally happy to not even use those cells at all, really. Possible solutions are peeling off cell labels or using an oversize cell in my true-18650 SureFire U2 (loading from the head end of the body).

I do have some small regret everytime I load up my 6Z, and seeing more than enough air gap between the cells & the body wall. I don't want that airspace, I'd much rather have aluminum. :-/

And the C3 that was overbored, that is a bummer, no bones about it.
Like the better machinists say, it's easier to remove material than to put it back.

Best regards,

 

[id30209]

@yazkaz: 3500mah comparing to 3400mah Fenix battery is evidently bigger. I was refering to 3400

@Kestrel: there's always an option to repair. Insert alu or brass sleeve with tight clearance in the tube. So tight that you need to freeze it and SF body heated that can fit. Once everything temp stabilized take another round of re-boring to proper size

 

[DrafterDan]

My general rule of thumb is minimum wall thickness of .050". A half MM is .019", too thin for my tastes. However, I do tend to over-engineer things

*Edit
Okay, I had to check. Just purchased this 6P body for a friends' gift. I measure 19.8mm. Minus 18.7, and you're not left with much. I do have one of the Bugsy bored 6P's, and it's never given me a problem.

 

[knucklegary]

Yep, too thin for me as well. Not enough wiggle room if bore is not concentric to oring groove, goodbye body..
I think Bugsy had a private machine shop do his boring. Never owned one of his bored 6p. Are the bodies finished reamed and honed like B.M. of Precision Electric performs?

 

[yazkaz]

My general rule of thumb is minimum wall thickness of .050". A half MM is .019", too thin for my tastes. However, I do tend to over-engineer things

*Edit
Okay, I had to check. Just purchased this 6P body for a friends' gift. I measure 19.8mm. Minus 18.7, and you're not left with much. I do have one of the Bugsy bored 6P's, and it's never given me a problem.

0.05" is around 1.27mm. That's too thick and many protected cells won't fit in.
0.019" is around 0.48mm (rounded up to 0.5). To reiterate, that's from the Fivemega spec (18.7-18.75mm) according to my local machinist. The FM bodies are also the first bored body mods I've ventured into and they are holding up very well.

BTW my machinist measures the neck area at 19.6mm. Minus the upper threshold of 18.99mm and you're left with just 35C (0.35mm) which he claims as still safe to use in general. Just don't induce any tail drop or any micro-cracks from the aluminum substrate could build up and inflect greater damage in the long run (up to total breakage). As for tailcap installation (battery replacement) the neck should be more than strong enough to withstand everyday usage.

Are the bodies finished reamed and honed like B.M. of Precision Electric performs?

Just honed mine with 600/1200/2000 wetsanding using CorrosionX and Rem Oil as lubricating medium, for the expected smoother (if not all smooth) surface in near-mirror finish. Bore diameter increases by 5-8C but that doesn't help much with protected 3500mAh compatibility.