Perfect fit: the deep carry clip for the BLF A6 tube light fits perfectly on the ZeusRay zoomie — the curve of the clip lines up nicely with the tailcap, and the clip fits snugly into a groove.

One-way swap: the head of the Convoy S2+ fits nicely enough — a bit loose — onto the battery tube of the BLF A6.
But not vice versa — the head of the BLF A6 is a bit too tight to fit the S2+ body.
[typos fixed, thanks Boaz]

Some “3W Police” 2xAA lights will donate one or two tube segments that fit some SK68 clones and some #3 zoomies, to make a 2xAA or a 3xAA out of the SK68 or #3 light.
(the LED head of the 2xAA 3W police has a plastic pill with a purple emitter; that can become a 1xAA with the leftovers, dim enough to be a decent kids’ toy I suppose. There’s a topic here for that.

Just thought to try this:

My EE X6-SE battery tube accepts heads from Convoy S2 and S2+

but they don’t make electrical connection, don’ t light

My EE X6-SE head does not accept either of two Convoy S2+ battery tubes, but it does accept a Convoy S2 battery tube.

One of my two red Convoy S2+ tubes takes my EVVA protected cell fine, the other tube is so snug I’d be afraid of getting the cell stuck in it (both of the red S2+ lights have every sign of being real, not fake — it’s just that their inner diameter happens to be just on the edge for this one cell I had out.

Lots more variation than I expected, even within the Convoy red S2+ lights I have here.

Another case of “slightly loose” works but “slightly tight” doesn’t, I think

EDIT — and note, your particular combinations of parts may vary, that’s the point of collecting first hand experience.

> one type of threading

I’d guess it’s more a failure of two things — repeatability and accuracy — so their tolerances are so wide that Lego-ing doesn’t work reliably.
Even assuming they’re using lathes that allows them to specify exactly what thread that lathe produces — how many operators, on how many different lathes, on how many days, are going into this production?
Seriously, these have to be beginners. Once someone’s competent to make truly interchangeable parts in mass production — that operator is going to be working on something more important than cheap flashlights.
Thank goodness, since that might be a nuclear plant or aircraft.

We’re getting the “training wheels” stage of industrial learning.

Quoting from the A6 thread at Thu, 09/10/2015 – 15:22

Quote:

body tubes are 2.732, 2.723, and 2.730 …
… tail cap measurements are .998, 1.000, and 1.000.
The tail cap that measures .998 only works when the 2.732 body tube, but i have to crank the tail cap as tight as I can

Quote:

That’s a perfect illustration why having a production that respects and understands specified tight tolerances matters.

There you have one that is less than .01 too short on one part, and less than .01 too long on the other piece, and — put them together, and hey, this one sample works fine.

Checking one product fails to detect the problem — too much variation around the spec — because some combinations of parts will average out to working properly.

See follow-on comments in that thread for more on tolerances and how you need really tight specs.

I posted a long quote on using micrometers that included:

Quote:

Repeatability is as much a function of my ability to achieve a consistent “touch” as it is the mechanical integrity of the mic.

Here’s an easy test – measure the same thing 10 times and see how much the readings vary.

I routinely see variations of +/-0.0001” on a good day.

There will be some variation — and the variations add up to this kind of problem when parts meet or don’t.

from a search, happened to notice a couple of mentions in other threads:

Quote:

Cheap UniqueFire C108 clone: http://budgetlightforum.com/node/38643
… Legos with the UF C8 and C12….

deal alerts: @ ebay, all flashlights below $5
… reviewed here: http://budgetlightforum.com/node/35779 …Legos perfectly with the Ultrafire 501b (at least the cheap host I bought from FT).

Mentioned by antenne, elsewhere:

Quote:

Hugsby XP1/XP2. It’s REALLY not recommended to put a 10440 in the XP-1, since the head is different from the XP-2. You could use the XP-2 one with a 10440 on the body of the XP-1 but not the other way around.

I just saw a “read somewhere” note that the MtnElectronics spacers (2 different ones) for the S2 and S2+ may also fit some other lights.
Anyone know for sure?

Tailcaps: the tailcap of my red Convoy S2+ fits and works correctly on the battery tubes for both an Eagle Eye BLF-X6-SE and an Manker A6. (only checked one of each)

The tailcaps for both of those black lights are too tight — they start but won’t screw onto the red Convoy S2+ battery tube.

As noted above — the tolerance for variation is so large on these that a sample of one isn’t proof of any general claim about what fits what.

I’d guess somewhere there are three bins — heads, body tubes, and tailcaps — and whoever assembles the lights just keeps fishing until he finds a complete set and calls it good.

It’s the Goldilocks approach to flashlight construction. Some are too small, some are too large, some are just right.

That’s an oversimplification — threads have to be defined by several different numbers — spacing, depth, slope of the cut, maybe more. We don’t get that kind of precision.
(Or we get the seconds, if there are some that good)

———— Has anyone checked the threads for the retaining rings? I don’t know if those are done to any standard or not.

My Convoy red S2+ tailcap legoes with the Jaxman UV tube, and vice versa.

(that as noted above isn’t always the case, and your tailcaps may vary — but these could be twins as far as the threads and depth go.

Quote:

the whole S2+ tail switch threads onto the A6 tailcap. unfortunately the A6 tailcap does not fit on the S2+.

http://budgetlightforum.com/node/36748#comment-832868

Quote:

This is an ultrafire c 308 battery tube that fits but just looks stupid

And just before that, in the same thread, also said

Quote:

digging through old threads shows the battery tube fits the Defiant.

hat tip to escereal
at: http://budgetlightforum.com/node/41481 — EAGLE EYE X6 XPL HI V21A

Quote:

escereal wrote: Received mine as well! I added a dollar more to receive a warm white XPL, and it is fantastic. … the tailcap of this X6 IS interchangeable with the BLF X6’s tailcap. Every part legos just fine. The threads are different between the two model lights, but they are able to be mixed and matched.