# Tailcap thread on Minimag?



## wquiles (Apr 8, 2012)

Best I can find out via the search is that the thread on the tailcap side of the minimag "appears" to be single start, 5/8"-28 UN, but I can't find if this just happens to be "close enough" or if this is indeed "the" correct thread for the minimag?

Anyone knows for sure?

Thanks,
Will


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## PCC (Apr 8, 2012)

I bought a 5/8" - 28 TPI tap for this purpose and it worked. The threads were not a tight fit, though. If you are doing it on your lathe I'm sure you can get the tolerances a lot tighter.


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## gadget_lover (Apr 8, 2012)

All of the minimags that I've examined have had threads that looked like they were cut with an old worn die. The crest of the threads tend to be slightly tapered and the thread form is not a proper ISO thread form. Look at it closely with a magnifier. The width of the valleys does not usually match the width of the peaks. 

Even so, it matches close enough that a proper 5/8-28 thread will work with it in most cases. 

Daniel


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## wquiles (Apr 8, 2012)

Thank you guys - I will give the 5/8-28 tap a try 

Will


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## wquiles (Apr 14, 2012)

Guys, I wanted to thank you again. I got the tap, and sure enough, it works perfect. I have not even cleaned these threads, and they still look perfect!












Will


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## 350xfire (Apr 14, 2012)

Cool. One of these days I'm going to mod one of the 10+ minis I have laying in the garage!


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## wquiles (Apr 14, 2012)

350xfire said:


> Cool. One of these days I'm going to mod one of the 10+ minis I have laying in the garage!



I got new production boards for my Battery Vampires (Joule Thief) arriving soon, so I am planning on some "projects" with 1xA and 2xAA mini mags 

Will


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## Essexman (Apr 18, 2012)

I can't remember where I read it, but I'm sure the thread is a Whitworth thread with 55° thread angle.


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## wquiles (Apr 18, 2012)

Essexman said:


> I can't remember where I read it, but I'm sure the thread is a Whitworth thread with 55° thread angle.


It might very well be, but the 5/8"-28 works perfect


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## PCC (Apr 18, 2012)

wquiles said:


> I got new production boards for my Battery Vampires (Joule Thief) arriving soon, so I am planning on some "projects" with 1xA and 2xAA mini mags
> 
> Will


I'm looking forward to see what you come up with.


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## darkzero (Apr 19, 2012)

Essexman said:


> I can't remember where I read it, but I'm sure the thread is a Whitworth thread with 55° thread angle.



Doesn't make sense why Maglite would use that thread.

I mostly hear people say it's 5/8"-28. But 5/8"-27 also works fine. As Daniel mentioned about the threads being so sloppy, I have MagAA tailcaps that measure closer to 27 tpi & some that measure 28 tpi. When I measure Kroll threads they are 28 tpi. 

I've never bothered to try a measure the threads on the body of a MagAA, Arc LS clickies, or a Streamlight Jr. But I have had Krolls & MagAA tailcaps fit 5/8-27 thread. I know it's not a reliable method of telling but I can get a 5/8-27 tap to screw into some of my MagAA bodies & some that don't. I can't get the 5/8-27 tap to screw into any of my Arc LS clickies.


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## Chicago X (Apr 19, 2012)

Essexman said:


> I can't remember where I read it, but I'm sure the thread is a Whitworth thread with 55° thread angle.



That is spot-on, and verified over on BLF.

Thanks, Will, for verifying that the "standard" 5/8-28 tap works well !!!

(Off to supply house) :twothumbs:


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## Essexman (Apr 19, 2012)

darkzero said:


> Doesn't make sense why Maglite would use that thread.
> 
> I mostly hear people say it's 5/8"-28. But 5/8"-27 also works fine. As Daniel mentioned about the threads being so sloppy, I have MagAA tailcaps that measure closer to 27 tpi & some that measure 28 tpi. When I measure Kroll threads they are 28 tpi.
> 
> I've never bothered to try a measure the threads on the body of a MagAA, Arc LS clickies, or a Streamlight Jr. But I have had Krolls & MagAA tailcaps fit 5/8-27 thread. I know it's not a reliable method of telling but I can get a 5/8-27 tap to screw into some of my MagAA bodies & some that don't. I can't get the 5/8-27 tap to screw into any of my Arc LS clickies.



Fo on, admit it, you just can't stand the idea that your American made iconic Maglite has a British thread size can you :nana:


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## gadget_lover (Apr 19, 2012)

Essexman said:


> Fo on, admit it, you just can't stand the idea that your American made iconic Maglite has a British thread size can you :nana:



It can only be said to be a WW thread if it conforms to the standard. My experience is that the thread is so sloppy that it does not really conform to any standard. The last time I looked closely the sides of the male thread was actually concave.


Dan


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## KC2IXE (Apr 19, 2012)

Chicago X said:


> That is spot-on, and verified over on BLF.
> 
> Thanks, Will, for verifying that the "standard" 5/8-28 tap works well !!!
> 
> (Off to supply house) :twothumbs:



That like folks "confirming" that tripod sockets on cameras are Whitworth? (Hin't they are not - I've actually spent the $$$ to buy a copy of the ISO spec to prove it)


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## darkzero (Apr 19, 2012)

Essexman said:


> Fo on, admit it, you just can't stand the idea that your American made iconic Maglite has a British thread size can you :nana:



Actually I could care less what Maglite uses. I still own Maglites (customs) from many many years ago but I don't remember the last the time I ever purchased one for myself. I just thought that it does not make much sense why Maglite, yes an American company (European founder) & because of which, would use a WW thread for the MagAA tailcap when all their other threads are UN. I support American made because it's my country but I'm not one of those guys who refuse to buy foreign or don't accept it. 

No one else here has stated what size it is definitely, only what has worked for them. Taking into account the "sloppiness" of the threads, just curious what means of inspection are the BLF guys proving their findings to be so sure?


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## Chicago X (Apr 19, 2012)

KC2IXE said:


> That like folks "confirming" that tripod sockets on cameras are Whitworth? (Hin't they are not - I've actually spent the $$$ to buy a copy of the ISO spec to prove it)



Did you buy the spec for the MMag? Have you measured?

The member who confirmed it makes _only _custom MMags, and AFAIK used 3 different sizes before landing on the Whitworth as the "best fit" over the 60-degree offerings.

Lest you claim "Red Herring," he shared all of the specs, rather than attempt to obfuscate them, in an attempt to expand the knowledge base.

Your dismissive tone is unnecessary and insulting.


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## gadget_lover (Apr 20, 2012)

I think Darkzero was justified and was neither dismissive nor insulting. He just stated his opinion.

The manufacturer is the only one who knows for sure what the minimag thread is. Inspecting the thread in a batch of lights (even a large batch) only tells you the range of deviation in your sample. It does not tell you what the range is supposed to be, nor what the design calls for.

Many people have had success with the tap that Will bought. If if works, it works. 

Daniel


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## Essexman (Apr 20, 2012)

Guys guys come on! Did you not see the face at the end of my post. I was just trying to inject a bit of humour into the whole subject. Sorry it didn't go down well. 

I've been an engineer long enough to know if it fits use it.


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## KC2IXE (Apr 20, 2012)

I'm dismissive on him using Whitworth for the simple reason is that basically NO ONE uses Whitworth anymore. No me, having looked at a lot of maglights, I just thing it's a REAL sloppy tolerance (like a 1) UN thread form. I've seen a LOT of loose tolerance UN threads described as Whitworth, so I have my doubts.


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## Chicago X (Apr 20, 2012)

gadget_lover said:


> I think Darkzero was justified and was neither dismissive nor insulting. He just stated his opinion.
> 
> 
> Daniel



You're right - he wasn't.


I was addressing KC2IXE


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## gadget_lover (Apr 20, 2012)

Chicago X said:


> You're right - he wasn't.
> 
> 
> I was addressing KC2IXE



Yeah, my mistake. I was reading from my cell phone. Should have double checked. 

The point still stands, that you can not tell what thread was specified in the drawings just by measuring what your sample IS, especially if the manufacturer is using very loose tolerances. 

I suspect the fact that some folks have used 27 TPI and some have used 28 TPI would indicate that the tolerances are VERY, very loose. 

Daniel


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## moderator007 (Apr 21, 2012)

I cut my 1AA mini's threads on the lathe using 28TPI. Seems to work well for me.







The tap is probably the easier way to go. If I do any more mini's I think I will just buy the tap and save some time. Thanks Will and PCC for the info.:thumbsup:


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## las3r (Apr 21, 2012)

Will or anyone where did u buy that tap ?


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## will (Apr 21, 2012)

I have done a number of cut down mini-mags using 28TPI. Every now and then the fit is not so good, maybe a little tight getting the tail cap in.

Is it possible that Maglite uses a non-standard thread? The only way to be sure would be to look at the actual engineering specs for the light.


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## wquiles (Apr 22, 2012)

las3r said:


> Will or anyone where did u buy that tap ?



Got mine from Global Industries:
http://www.globalindustrial.com/

Will


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## PCC (Apr 22, 2012)

moderator007 said:


> I cut my 1AA mini's threads on the lathe using 28TPI. Seems to work well for me.
> 
> The tap is probably the easier way to go. If I do any more mini's I think I will just buy the tap and save some time. Thanks Will and PCC for the info.:thumbsup:


Interestingly enough, I sold my tap after I got my lathe. I never was able to easily align the tap with the tube, though the lathe would facilitate that, now that I'm thinking about it. What I used to do was to run the tap through the tail cap threads all the way in to about the half way point then cut it and dress it on the mill. This resulted in threads that were true and my hands got a workout, too


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## moderator007 (Apr 22, 2012)

PCC said:


> Interestingly enough, I sold my tap after I got my lathe. I never was able to easily align the tap with the tube, though the lathe would facilitate that, now that I'm thinking about it. What I used to do was to run the tap through the tail cap threads all the way in to about the half way point then cut it and dress it on the mill. This resulted in threads that were true and my hands got a workout, too


Figure it save me quite a bit of time, over having to set up the change gears ever time. Just put the tap in a drill chuck in the tailstock and thread right after I have cut the mini to length while it still centered in the lathe chuck.


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## darkzero (Apr 23, 2012)

I was curious to see if the internal threads were any better & wanted to measure them too. Well the internal threads of the body aren't any better than the tailcap threads. You could get away with using 28 tpi, 27 tpi, & .09 P(mm) just fine as long as your pitch diameters are undersized if even needed. 














Unfortunately I only had one donor to measure. I think I do have the end of an Arc LS AA Clickie pack somewhere to cut open, if I can find it.

I agree with Daniel, the tolerances are so loose that I would find it hard to believe anyone who claims they have came up with a definitive answer simply by measuring a few samples. I'm curious what it would look like in a comparator. I've only used a comparator a couple of times to inspect external threads. Is it possible to inspect internal threads in a comparator? Maybe make a mold out of plastic or something?

I don't think the threads are cut, I suspect they must be formed & rolled, & who knows how worn their tooling might be. I'm sure there must be some intention for loose tolerances to help prevent any fitment issues with replacement parts. Better loose than sorry _for them_, but I don't like the sound of that.


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## PCC (Apr 23, 2012)

moderator007 said:


> Figure it save me quite a bit of time, over having to set up the change gears ever time. Just put the tap in a drill chuck in the tailstock and thread right after I have cut the mini to length while it still centered in the lathe chuck.


As darkzero stated and what I alluded to earlier, using the tap leaves you with a loose fit between the tail cap and body. I forgot to mention this as another reason for selling the tap. Cutting the threads on the lathe will allow you to get the tail cap to thread on with a lot less slop.


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## moderator007 (Apr 23, 2012)

Is the tap slop worse than the factory slop?


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## PCC (Apr 23, 2012)

For me it was pretty bad. Worse than factory for sure. That may have been my particular tap, though.


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## moderator007 (Apr 24, 2012)

Will, do you care to comment on the slop with the Global Industries tap. Worse than factory or about the same.


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## wquiles (Apr 24, 2012)

moderator007 said:


> Will, do you care to comment on the slop with the Global Industries tap. Worse than factory or about the same.



I threaded 4-5 pieces (practicing technique, etc.) and I tried the resulting threads with 2-3 tailcaps. Quite honestly the threads with the tap I bought felt to have about the same slop as the factory. Quite hard to tell apart.

Will


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## moderator007 (Apr 24, 2012)

Thank you will. :thumbsup: Factory slop is good enough for me. I just didn't want it to have so much slop to the point of a potential failure.


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## wquiles (Apr 24, 2012)

moderator007 said:


> Factory slop is good enough for me.


Remember that there are other variables when cutting threads, and that the o-ring engagement area and the amount of o-ring compression also contribute greatly to the overall "feel" when engaging the tailcap. That is one area that you can experiment as I found that the o-ring engagement using the OEM measurements was way too loose for my taste - I designed mine to fit a tad tighter.

Will


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## moderator007 (Apr 24, 2012)

wquiles said:


> I designed mine to fit a tad tighter.


I also did the same thing Will.


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## wquiles (Apr 24, 2012)

moderator007 said:


> I also did the same thing Will.


Great minds think alike ... :devil:


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## 350xfire (Apr 25, 2012)

Chicago X said:


> obfuscate them



What he said!!!


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