Is there a reason to lockout the tail cap instead of the head?

OK, got a new Fire Flies E07.
I will probably only use mechanical lockout for a few reasons, mainly because I carry it in a holster and I have a tendency to activate lights while leaning back in the car.
On this light I can lockout either with the tailcap or the tube at the head.
It would be better to lock out at the head, since in simple terms there is more to grab (in firearms terms, it is a gross muscle movement rather than a fine movement).
Is there any reason to only use the tail for a lockout? This was a $75 light, I have no desire to ruin it.
Thanks for any info.

If locking out the head works, no real reason not to do it, it’s just not as universal. Many lights are glued at the heads, or use loosening the head as a UI mechanism, or just don’t anodize those threads, either for cost savings or to ensure compatibility with longer cells.

This one uses circular contact points on the front and back boards, so the current does not go directly through the threads, only through the ends of the tube.
So as long as it won’t do any harm that would be a better way to do it, for me.

One of my E01 lights locks out with a slight twist of the head, the other you have to almost take the head off all the way. That is the earlier one with the sharp fins, they must have made some manufacturing change.

Or the contact ring on the driver board is in contact with the threads or tube I guess. Both of the E01 are clear, so the one may not be anodized on the inside. The E07 is grey and the threads inside the head and on the tube are clearly anodized so that may be why.

Just for giggles I swapped the heads on the two E01’s
The threads on the early model must not be anodized, the head from the newer one behaves the same on either body.
And the older one behaves the same on either body.
My conclusion that that the threads are not anodized on the first version head.

I don’t know about that light specifically, but usually, the flashlight will be made to open at one place to change cells. On most lights, it will be the tail. At that joint, it is expected to have many on/off cycles, and at other joints it is expected to never move. So the threads may be better at the joint that is expected to be opened and closed repeatedly over the lifetime of the light. If your light has equal quality threads at both joints, it might be fine to open it either way. If both ends have good anodizing and square cut threads, then they should be functionally equivalent. Check for joint lubricant as well, and add some if the threads don’t already have it.

The threads are different on the two ends.
Square on the tail and fine on the head,
both appear to be well lubed and screw on and off easily

Well, then it seems to me that:

  1. The tail threads are the ones intended to be used for changing cells. but…
  2. Either will work if they are both anodized and lubed. If the fine threads are not anodized, then they will wear out faster, even if they’re lubed.

It’s just easier for me to lock out the tail, since it’s more intuitive.


Keep in mind, we are only talking about a twist of a couple of mm. Not a quarter turn. Not an eighth turn. Literally 2 or 3mm shuts it down.

But if you really wanted to put your light into service in a hurry, a 2 mm twist on the fat part is way faster and less likely to cause a miss due to sweat, blood, grease or whatever.

I always lock/unlock my Emisars at the head since I can quickly and easily do it one-handed.



A couple of millimeters is 2 full turns as usually the thread pitch is 1 mm (give or take some 0.25 mm) on square / trapezoidal threads.

As a machinist, square / trapezoidal threads are designed for easy and repeatable engagement. Finer threads aren’t as sturdy and the anodization may flake off. If the thread tolerance fit is loose, then there is a probable chance that it may bind as you apply a force not in line to the thread axis (shallow threads lock-up). Much to your dismay, tailcap lockout would be my choice.

Is that Common Core math? It is not two turns, it is literally just cracking the flush fit. You literally could not fit a hair in the gap. I know I am dumb, especially in math, but what you said makes no sense to me.

Then it’s not 2 mm.
A millimeter is about .040”
Check a ruler.

Edit; maybe you should have said a couple of thousandths (.001 to .002”).
Edit 2: a hair’s thickness is .004” in machinist’s terms.

One of my lights, fiicr which one, though, had the ano “wear off” just enough that a fractional-turn to lock out just isn’t enough anymore. And even when “locked out” but the tailswitch on, pressing on the tailcap can in fact turn it on again. Gaaah, trying to remember which one…

Anyway, whichever threads are made to be unscrewed should be the ones used. Given my druthers, I’d even use weak loctite to lock the head-to-tube threads so that they don’t accidentally unscrew.

I think he meant a couple of millimeters of turn “rotationally” around the circumference. :wink:

My TK15 (Thorefire) has shallow 60º threads. After a year of locking out, the threads’ anodization wore out some. Bugger turned on in my rear pocket at high (~1100 lm) and melted a clean hole in the nylon holster. Did smell it though!

When I was an apprentice…