The flashlight thread in square cut and standard triangular cut

Minos2014

Newly Enlightened
Joined
Mar 7, 2014
Messages
124
I just found some flashlights thread have 8 circle of solenoid coil (like photo 3.1). The Screw pitch is relatively narrow

64b35d2d-8ef1-0fe7-cb40-bba7ae2bceda.jpg


And some flashlight has only 4 circle of
solenoid coil.(like photo 2.1); And the Screw pitch is relatively larger.
473e2512-5755-63d8-2981-a082eff23485.jpg


And some flashlight the thread in Square cut (like photo 1.1)

b91b7607-b449-c7eb-1fc3-61dd33148202.jpg


Some thread in standard triangular cut.(like photo 4.1)
de8360d7-6d94-2e2e-97bb-0bddbd342634.jpg


Even in one flashlight the head thread and tail thread is different. See the below photo 6.1 "Tail thread" is square cut and biger
Screw pitch.
06945c74-56e6-4faf-3c79-1aec1750c980.jpg


And the head therad is standard triangular cut (see photo 6.12) and relatively narrow screw pitch
ab2066f4-cf7b-5157-8aa4-b3cb385b405a.jpg


About the thread,Is there any one know what kind of thread is good for flashlight? Do you think the thread type is very importand to a flashlight ? IMO . The square cut and narrow screw pitch will be good for the flashlights.Is there any different thread here in the lights?

Thanks
 

StorminMatt

Flashlight Enthusiast
Joined
Oct 30, 2012
Messages
2,263
Location
Norcal
Square threads have their advantages when it comes to flashlights. Its chief advantage is the fact that tightening the joint doesn't cause the female part to expand. Therefore, there is less of a chance that, say, a tailcap will break from over tightening. And there is less chance of the tailcap expanding and skipping a thread (which causes damage). Also, with triangular threads, the chances of these two things happening increase as threads wear. But this does not happen with square threads. So square threads are useful for parts which are frequently removed. This is why the light you mention uses square threads at the tail and triangular threads at the head. Since the head is removed FAR less than the tail, there are fewer advantages to using more difficult to cut (and more expensive) square threads there.

As far as pitch, a larger pitch (fewer threads per inch) is generally better. This is for much the same reasons as listed above for square threads. Although larger pitch triangular threads can still cause the female part to expand, it is far less likely that it will expand enough to skip. This is because it would need to expand more. However, deeper threads require more material, which tends to make things like tailcaps larger in diameter.
 

Minos2014

Newly Enlightened
Joined
Mar 7, 2014
Messages
124
As far as pitch, a larger pitch (fewer threads per inch) is generally better. This is for much the same reasons as listed above for square threads. Although larger pitch triangular threads can still cause the female part to expand, it is far less likely that it will expand enough to skip. This is because it would need to expand more. However, deeper threads require more material, which tends to make things like tailcaps larger in diameter.[/QUOTE]
-------------------------------------------------------------------------------------------------------------------------------
Hi . Storminmatt

Thanks for your answer. I am appreciate you read my post carefully. Generally i agree with your opinion.So you think if one flashlight use Square threads in the tail and triangular threads in the head is more perfect choice.

But why you say a larger pitch (fewer therads per inch )is generally better? I think larger pitch means compactedness was reduced,which means easy to loose.

What's your thoughts?

 

Richwouldnt

Enlightened
Joined
Apr 17, 2011
Messages
314
Location
Reno, NV
Larger pitch threads are deeper cut so more material wear is needed before they wear enough to start causing problems. Also less likely to be cross threaded when screwing two parts together.
 

TEEJ

Flashaholic
Joined
Jan 12, 2012
Messages
7,490
Location
NJ
Generally, to avoid the problems a flashlight can run into, a finer pitch means a part has to rotate more times to fall off, and, that there are more ridges to brace the part against force/damage. It can also increase the leverage/torque advantage in screwing parts together, as its a more gentle ramp. (A finer pitch is MORE threads per inch, not fewer though, just to clarify)

Some people find its easier to cross thread a finer pitch than a course thread pattern, but, that's mostly on poor threads that don't ramp properly to start with.

Deeper threads also add strength, as they also increase what the part is braced against.

A longer section with threading, so that the two parts are joined by a larger overlapping area, also adds strength, by increasing the length of the bracing between them.

The advantages of square threads was discussed already, and, again, the thickness of the ridge that is braced against adds to the strength as well. The machining on square threads tends to be better than on triangular profiles, as its a more advanced thread technique that costs more, etc. This means the triangular threads might be rougher/less well finished, and more prone to cross threading, etc. Some are finished quite well though, so its QA/QC dependent, etc.

A large overlapp of fine square threads can result in a more water/dust proof connection as well.

As mentioned, if you make the threads TOO deep, the matching female end has to be proportionally larger in diameter to fit over it and have enough wall thickness, etc. When bored out too far, the walls can be too thin, and that also reduces strength. If the OD stays the same, that means the male end's ID may be shrunk to make room, or, again, wall thickness may suffer, reducing strength.


Some of the above issues are all questions of DEGREE on a flashlight, in that a light without all the "stronger choices" may work just fine anyway, depending on the design.

Sometimes, missing ALL the above features, can result in the light not being durable.


Large pitch threads with a small overlapping areas tend to fall apart more easily under stress than finer thread pitches with larger overlapping areas. I've had some eBay specials that literally fell to pieces when attached to a weapon and whacked with recoil forces for example.

Some of these lights worked fine as flashlights, as long as they were never stressed, but, when stressed, they can fail, sometimes catastrophically. The walls can fold/collapse, poor threading can rip loose/tear off the threaded part, and so forth. Its not pretty.


:D
 
Last edited:

NoNotAgain

Flashlight Enthusiast
Joined
Jan 25, 2014
Messages
2,364
Location
Blue Ridge Mountains, VA
When it comes to threading soft materials like aluminum, a coarse thread is preferred as it is easier to manufacture. Threads are fabricated either by cutting or rolling the thread. A rolled thread is faster from a production standpoint to fabricate, but initial tooling costs are higher. The standard 28 degree thread pitch lends itself to produce a clean thread with low cost.

Square threads are called ACME threads and have to be cut not rolled. Acme threads are used in applications that are subject to higher torque loads.

I can't speak for all of Surefire's lights, but my M3, M4, M9 and P6 series lights, all of the male threads are roll formed threads on the light bodies. They are very smooth to operate while some of the lesser quality lights are a lot more difficult to screw together.
 

Minos2014

Newly Enlightened
Joined
Mar 7, 2014
Messages
124
When it comes to threading soft materials like aluminum, a coarse thread is preferred as it is easier to manufacture. Threads are fabricated either by cutting or rolling the thread. A rolled thread is faster from a production standpoint to fabricate, but initial tooling costs are higher. The standard 28 degree thread pitch lends itself to produce a clean thread with low cost.

Square threads are called ACME threads and have to be cut not rolled. Acme threads are used in applications that are subject to higher torque loads.

I can't speak for all of Surefire's lights, but my M3, M4, M9 and P6 series lights, all of the male threads are roll formed threads on the light bodies. They are very smooth to operate while some of the lesser quality lights are a lot more difficult to screw together.
-----------------------------------------------------------------------------------
Do you think is this an important factor to decide a high quality light or not ?
 

Minos2014

Newly Enlightened
Joined
Mar 7, 2014
Messages
124
OK . I got it .I think Square cut thread is necessary for a tactical flashlight and gun light.
 
Joined
May 19, 2005
Messages
910
Location
Seattle, WA
OK . I got it .I think Square cut thread is necessary for a tactical flashlight and gun light.

I would not say that. Most lights, including SureFire and Streamlight use triangular threads. There are some benefits to square cut threads, but I don't believe they're worth the extra cost it takes to make them. If you want a good gun light, you should look at user reviews instead of making your decision based on the type of threads they use. You might find that your lights have other issues when they need to absorb the recoil from a gun.
 

TEEJ

Flashaholic
Joined
Jan 12, 2012
Messages
7,490
Location
NJ
The overlap between the lengths of the threaded sections makes a large difference in a weapon light...an inch of threading will hold up better than a 1/4" and so forth. Triangular threads if well made, are ok if deep and long enough in overlap, etc. Square profile is better, but, not crucial if all else is strong.
 
Top