# N cell project: machinist needed



## glire (Feb 7, 2006)

[size=+1]UPDATE: drawing done[/size]






I'm trying to design a simple small sized flashlight based on one N cell (about 2/3 AAA).

Basically, inner diameter is 10.6mm, outside 15mm and overall length about 46mm. Inside body length is about 31mm (left part). Head is 16mm (right part). A thread will fix head on body (thread 4mm length).
The rightmost head inner diameter is 12.0mm.
Parts should be metal (aluminium), at least the body.

Before going further, here are some questions:
Can these parts be easily machined?
Are there any questionable issues (thickness, body depth, etc, a 16mm longer body could be done for a AAA flashlight version later).
Tell me what you think.

PS: of course, some day I will ask someone to do the job :wave:


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## xochi (Feb 7, 2006)

*Re: N cell project*

Hey, check out the peakledsolutions shasta. It comes like your light. It may be a bit larger though. Peak lights tend to be large compared to the cell they run on. 


That would be a cool little light with nichia cs leds. I'd be interested in buying if they are reasonable. Their are also good 500ma nimh ncells available.


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## CroMAGnet (Feb 7, 2006)

*Re: N cell project*

Yes I use a LiON 10280 in the 3LED Shast without a problem. It's EXCELLENT

BUT we need yourr SMALLER light


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## glire (Feb 7, 2006)

*Re: N cell project*

Well, it seems I don't know yet CPF. Until now I neglected manufacturers' forums. There are some interesting stuff there, indeed 

I just looked at Peak's Sasha. Cute and affordable. But runtime charts...

Yes, that's what I'm trying to do: use AW's 10280 LiIon in a simple light smaller than an AA cell. With 3 good 5mm LEDs we could expect usefull brightness and +2 hours runtime.

Comments are welcome.
Thanks again.

EDIT: just found this now https://www.candlepowerforums.com/threads/101304


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## glire (Feb 8, 2006)

*Re: N cell project*

I updated the initial picture with measures. My AW's 10280 LiIon is 10.25 to 10.40mm diameter by 28.5mm length.
Here is a picture of cells (with a Fenix L1P and a choco can )




Wouldn't it be nice to have a 3 LED light smaller than a AA battery? And no, no titanium here. This is for a non luxurious but usefull light.


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## glire (Feb 20, 2006)

*Re: N cell project*

OK, now it's offical 
Can someone machine two cylindrial pieces for me? (with compensation)
Post #1 has been updated with a cut view and measures.
Feel free to ask any question.






PS: what a pain drawing with Paint :toilet:


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## olephart (Feb 21, 2006)

Since you asked...

A quick look indicates no clearance between the head and body.

Why Metric? Most U.S. hobbyists are set up to thread and measure in inches. You will probably find it more difficult to get help with metric threads and dimensions.


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## TENMMIKE (Feb 21, 2006)

olephart said:


> Since you asked...
> 
> A quick look indicates no clearance between the head and body.
> 
> Why Metric? Most U.S. hobbyists are set up to thread and measure in inches. You will probably find it more difficult to get help with metric threads and dimensions.


 i am a aerospace machinist and work with both types of measurements every day, however i am unable to help him out , but to convert simply divide his measurements by 25.4 to arrive at our inch measurements, it seems that his tightest tolerances are +0.05mm -0.000mm and -.05mm +0.000mm meaning he is probably trying for a nominal fit on these call outs of +.025mm OR -.025mm (depending on which one we are looking at), that works out to approx +-.001 inch( one thousandth of inch)per callout, these are not outrageous specs but would certainly require somebody to pay attention to what they are doing and many non industrial grade tooling / machinery might be hard pressed to maintain that tol.


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## glire (Feb 21, 2006)

Thanks for answers.

The clearance: there is between 0.00 and 0.10mm, I thought it was clearly marked with given tolerance, and far enough value.

Metric: outside USA, you know, there is something called "rest of the world" 
Seriously, AFAICK the metric system is the international standard for measures. Anyhow, just divide by 25.4, or 25 for simplicity.

So, it seems tolerances are quite tight for hobbyists. Don't take them as a "must be" and in any case I will not be able to check them with precision as my caliper has 1/20mm (0.05) precision at best.
You can change all marked 0.05 tolerance by 0.10, make an imperial thread if you like with a pitch of about 1/32", and set the clearance between body and head to any acceptable value. I just need to insert a N cell, a small spring, a 1/2" diameter 2mm thick PCB with three 5mm LED (sorry, I mean 0,19685" LED )

Thank you.


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## gadget_lover (Feb 21, 2006)

The point where most people make mistakes are the threads. Using 32 tpi, the body will have about .030 inch (.8 mm ??) wall thickness at the threads. That's OK in my experience. The .7 mm head thickness at the threads should also be OK.

Is the sandwich going to be secured by that 1mm gap between the end of the threads and the central bore of the head? If not, what will keep the PCB from being forced out the front?

Daniel


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## greg_in_canada (Feb 21, 2006)

What's the reason for the thick metal in the bottom? Do you want a bump in the middle to contact the negative of the cell (otherwise the heatshrink on the cell may prevent contact)? Or maybe keep it thick and do a non-thru drill and tap then put in a stainless steel screw for the negative contact.

Greg


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## greenLED (Feb 21, 2006)

you may want to add a small convex "bud" on the inside of the body to provide a secure negative contact with the battery. As it is right now, if you use a cell that has a wrapper, the bottom end of the battery won't touch the bottom of the body.


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## olephart (Feb 21, 2006)

It has nothing to do with dividing by 25.4. It has to do with having the gearing on a lathe to cut metric threads.

Perhaps you should solicit help in the rest of the world or pick some threads that almost anyone (in the US with a lathe) could produce. 

If both parts are cut exactly as drawn, you have no clearance. They are both 13,6. Somewhere in the tolerance range there is clearance. Somewhere there is not. Since an acceptable part can lie anywhere in the tolerance range, you are specing parts that won't fit or would be quite painful to make.

It's not a question of being able to make parts that have no clearance. The question is who would want to spend the time - this isn't a rocket ship part.

Your response seems to be, well, just change stuff and make it fit. My comments were offered to make it easier for you go get someone to help you out for a reasonable price.

Sorry if you were offended.


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## gadget_lover (Feb 21, 2006)

I just noticed the first post shows the mounting of the circuit board. Sorry bout that.

But I also see that .8mm pitch is called for. That has a sharp V depth of .69mm, and you only have .70 mm wall thickness in the head. That will not be enough, IMHO. 

The formula for thread height I'm using is 0.866025 * .8 = .692820 . If someone has a proper tap for the thread you can get to 0.54127 * .8 = .43301mm . Even so, that only leaves .27mm ( .010 in) thick at the threads. Kinda thin. I'd add another 1/2 mm to the head outer diameter

My EDC has a section that is only .022 thick and that's about as thin as I want to make things that may take some stress. It's made of 2011 so it's a little stiffer than 6061.

I could, of course, be all wet 

Daniel


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## gadget_lover (Feb 21, 2006)

Oh... BTW. With stock gears on a 7x10 lathe you can do 0.7993 pitch. That's per my gear calculation program at http://www.tanj.com/cgi-bin/tpi.cgi. 

With the 21 tooth gear from little machine shop you can come within a fraction (.7501mm) of the .75mm pitch.

Since this is a 1-off light, the exact thread pitch is not as important as getting a good fix between head and body.

Daniel


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## HarryN (Feb 21, 2006)

Daniel - I am reading his drawing slightly differently, although possibly incorrectly. I think his wall thickness at the thread point is 2 x that.

Glire - Paint is difficult to use. I design my lights in excel. Not exactly easy, but easier.

I try to keep wall thickness at or above 1mm if at all possible. If it goes thinner, it has a tendency to become a sharp edge.


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## gadget_lover (Feb 21, 2006)

Good catch Harry. The 13.6 appears to be the root of the female threads, not the crown. Given that....

The threads should be fine as long as the proper thread form is used. It will probably be kind of tight getting the circuit board past the threads....


Daniel


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## CNC Dan (Feb 22, 2006)

glire said:


> Thanks for answers.
> 
> Metric: outside USA, you know, there is something called "rest of the world"
> Seriously, AFAICK the metric system is the international standard for measures. Anyhow, just divide by 25.4, or 25 for simplicity.


You should fill out your location in your CPF profile( the country at least), so people know where you are. You might find some one close by willing to help.
Many people won't want to get involved if they don't know where you are.


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## glire (Feb 27, 2006)

Here I'm back with answers.

Metric and imperial:
This is not important I guess, but threads indeed.
In metric, V shape depth formula is 0.613*pitch (told to me, but unverified). A 0.8mm pitch gives ~0.49mm V deepth. That's within measures and tolerances I gave which should give an overlapping thickness body-head between 0.40mm and 0.50mm (if I'm not wrong).
Gadget_lover, given your formulas, it seems the V shape is much more deep with imperial threads than with metric. 52 TPI seems needed for my depth (which is a pitch of 0.0192"). Is that correct?
Actually, I think someone should help me here by giving the "good" thread for my dimensions.

Electrical body depth contact:
A conical spring should fit in there. I'll use a spring from any battery holder (from an old toy, old radio...), et voilà!
The machined "shape" is not very important on that part, as long as I can fit the spring and the battery. If it can be flat, then perfect. If a tool needs to make some cone which can't be flatten, then OK (with a minimal depth of 31mm).

Body bottom thickness:
Yes, I left 5mm. It's thick. That's because I don't really know how would look the interior "shape" (see my previous point: flat? conical?). With such thickness, the body interior end has a wide margin shape style. A hole could also be easily drilled or milled from the outside for a lanyard or key-ring.

PCB:
The 1mm gap between body and head is for the PCB. Three LED and three resistors will be soldered. I don't really feel the need of a regulator for this simple project. That's the advantage of LiIon: a step-up is not even needed.

My location: Brussels (Belgium). Old Europe, metric world (I think even UK "joined us" for that ).

Thank you.


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## gadget_lover (Feb 27, 2006)

If I'm interpreting correctly, on the head you have a 12.6 mm bore that you want to thread. The max thread depth should be .5mm.

For some reason, I was starting with the 13.6 bore as the root of the thread and working backward.

The .613 multiplier for the pitch is the "basic height of an external thread". The internal equivilent is 0.54127. The basic height is after you subtract the rounded root and the crest. That's why I said you'd need a proper tap or a proper single point threading cutter. You can hand ground tools for a specific thread size. Well, others can. I can't.

If you have only tools with a sharp 60 degree tip, you can still make the cuts. The root is not rounded, so you end up with a sharp V. Same shape but the very bottom of the thread has a sharp v shaped bottom. You can still do the flattened crest with any tool.

Go with the .8 or .75 mm pitch and you should be fine. You actually have 1.8 mm between the 12.6 bore and the 16.0 outside wall. 

Some good thread info at....
http://www.colinusher.info/Livesteam/mewdata.html . Also good info in Machinery's Handbook.


Daniel


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## glire (Mar 1, 2006)

gadget_lover said:


> If I'm interpreting correctly, on the head you have a 12.6 mm bore that you want to thread. The max thread depth should be .5mm.


Yes, exactly.
I updated the drawing on the first post.



gadget_lover said:


> For some reason, I was starting with the 13.6 bore as the root of the thread and working backward.
> 
> The .613 multiplier for the pitch is the "basic height of an external thread". The internal equivilent is 0.54127. The basic height is after you subtract the rounded root and the crest. That's why I said you'd need a proper tap or a proper single point threading cutter. You can hand ground tools for a specific thread size. Well, others can. I can't.
> 
> ...


Thanks for the link about threads. I understand now what you were meaning about "sharp V". So I updated the drawing with "flat" crests and "round" roots. Given formulas in your link, actual depth is about 0.433mm for a pitch of 0.8mm (iso metric). I reflected them in the drawing ("rounded" to 0.45).
Instead of iso metric threads, if a standard whithworth thread has to be done, it should have a pitch of 0.7mm to obtain about the same actual depth (0.027").

Still nobody can make those pieces for me? Thanks.


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## HarryN (Mar 1, 2006)

Gire - I will discuss the project with my brother and see if he is interested. There are some interesting challenges to the project. 

1) The walls are very thin, which likely means that several attempts will be needed, and success is not certain.

2) The thread is a custom / non standard size, but based on a metric standard concept. This makes sense for a machine shop, but most hobbyist do not have the tools to pull that off. That is why there have been questions and comments about the exact thread shape needed. Hobby lathe people are usually set up for sharp thread shapes.

A custom tap to exactly make what you want is about $ 200 and will only be useful for this one project.

3) A CNC lathe might be able to do most of this pretty easily, but the thin walls require lots of light cuts. Each piece you have drawn there might take 2 days to produce one "in spec" on a hobby lathe, by the time you include setup.

A CNC shop would charge about $ 1,000 for that work.

A very generous home hobbyist might do it for $ 25 - 50 / hr, and you are looking at 20 - 30 hours of effort for a "one off".

4) This is not a criticism, but the outside of your light is very smooth. I am not sure how many people would really want a "smooth" light body that cost almost $ 1,000 to make. With the walls that thin, it will be difficult to texture.

I think the reason no one is jumping at this is that we are not sure if you are ready to throw that kind of money at this light, when there are so many lights on the market that are just a little bit larger. Perhaps you can comment on this aspect.

The cost of custom machining is very high, no matter where it is done. Even my brother charges me $ 30 / hr, with a 4 hour minimum, plus tooling and food. (that is really cheap) I have some lights with a lot of $s in them, that have ended up looking pretty simplistic.


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## gadget_lover (Mar 1, 2006)

Well, the good news is that it's totally do-able on most home lathes. The tolerances are loose enough that even I could do it. You might have to settle for an approximation of the .8 pitch if it's done by a hobbiest. The 32TPI is 0.7937 mm pitch. Many hobby lathes sold in the US do not come with the necessary change gears to cut metric threads. 

This should not be an issue unless you are trying for interchangability. Realistically, most if us who machine at home hand fit the matching threads. That way it does not matter if the threads are .003 too shallow on one part, you make up for it by compensating on the other part.

The good news is that your plans are complete enough to take to a machine shop and have it made. (I think) The bad news is that I've too many other projects going on, so I'm not offering to do it.

Daniel


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## greg_in_canada (Mar 1, 2006)

If you are using a spring in the bottom how will the light turn off? Will you be using a foam donut (like the Arc AAA) at the top to force the postive contact to break contact when you loosen the head?

Greg


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## gadget_lover (Mar 1, 2006)

I see harry and I typed our messages at the same time. 

To make it easier to find an amateur machinist, you might amend the spec to allow for "close" but not on spec. This allows for errors in machining. 

As an example. The OD does not have to be exactly 13.5 mm. It might be a touch less if the machinist cuts off a few thousandths too many. That's really OK as long as the head dimensions are altered to match. Why does this matter? It matters because machining is a multi step process. You have to bore, knurl, turn, cut and thread. If each step has to be perfect, you may have to start over after spending an hour doing the first two or three steps. This adds to the time and expense. A CNC machine or a professional would be expected to do it exactly to spec.

As a general suggestion, when designing a light (or anything else) it's best to start with standard dimensions and threads. The diameter of 13.5mm is just right for the light, but it's .5305 inches. This means that the machinist has to start with a bar larger than 1/2 inch and reduce it to .530. In this case it's not bad, since the head will be .5895 inches so a 5/8 inch bar (.625 inch) will probably be used for both. In a larger light it could make a lot of difference. Again, just general advice.

Daniel


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## glire (Mar 1, 2006)

greg_in_canada said:


> If you are using a spring in the bottom how will the light turn off? Will you be using a foam donut (like the Arc AAA) at the top to force the postive contact to break contact when you loosen the head?
> 
> Greg


Positive contact is done by direct contact between battery and PCB center.
Negative contact will be done by the body on a donut on the same PCB. Twisting the head in/out should turn on/off the LEDs (well, I expect it).

HarryN, Gadget_lover,
Thanks a lot for your responses.
More to come after some thinking (and sleeping ).


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## glire (Mar 23, 2006)

Job done!





For right to left, back:
Nuwai TM-311H (excellent machining IMO)
Triton P1 (average machining IMO)
Fénix L1P (very good machining IMO)
SE FL319 AAA (amazing little light from http://candlepowerforums.com/vb/showthread.php?t=108812 )
My N cell proto (good machining IMO, no coating)
NiMh AA cell
NiMh AAA cell
LIR123 cell
10280 cell (from AW)
Inox M14 bolt

Front:
My N cell proto open
My N cell proto with an Oring and the 10280 inside
Inox M14 bolt after having been passed on a lathe


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## greg_in_canada (Mar 23, 2006)

Cool. Who did it for you? A CPFer?

Greg


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## gadget_lover (Mar 23, 2006)

Looks nice. I see you added an o-ring groove since the last time I studied the drawings. Good idea. I find an o-ring also helps in that it prevents the head from unscrewing in your pocket.

Do the threads of the head hit the o-ring? The drawing shows a 4mm male thread on the body with the o-ring right next to it. The head, on the other hand, has a 2mm band for sealing the o-ring followed by the 4mm female thread. The stop for the male thread would be the back of the circuit board. This can allow the threads to engage up to 5.5 mm deep.

It is probably not a problem since the battery should prevent the threads from ever being screwed all the way down. If you notice the 0-ring getting 'chewed' you may want to add a small washer.

Daniel


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## Changchung (Mar 23, 2006)

Hi my friend, this N flashlight is for sale??? or maybe you can sell me one??? Or two....


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## glire (May 18, 2006)

Well, as you can see I spend more time buying flashlights than progressing in my little project 

I just started learning Eagle Lite to draw PCBs. Only after having made a PCB I will have, maybe, something that outputs some light... 

I the meantime, I tried to anodize.
I gave 2 prototypes to a company who just ruined them after holding them for 5 weeks. I assume he had no interest for my prototypes, despite some initial hypocrit interest...
Another company anodized 5 prototypes in black. He also did some mechanical coating to remove micro-scratches on 3 of them. 3 days for this job.
The ano process shows that the machining has been made on two different types of aluminium for head and body. The head seems harder and keeps a brilliant aspect. The body straches easier and is becoming darker (I assume it's some kind of oxydation), looks like not a high grade aluminium.

The machining and ano have been done by professionnals. No CPFer helped yet...
I'll give numbers when finished.

Changchung, why not if you're ready to pay 50€ at least for something that will exist in 8 samples only 

Seriously, with some help and interest, this could be doable. Not cheap, but affordable.
HarryN predicted $1000 for the machining of one prototype. I'm fortunatly far below for ten.


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## glire (May 18, 2006)

Oh, I forgot one very important thing: actual N cells seem to be 11.5mm diameter, not 10.5mm like AW's 10280. A23 cells (12V) should fit like the 10280.
So a generic N cell light would be a little more fat.


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## tvodrd (May 18, 2006)

Actually, an N-cell light is possible starting with 1/2"/12.7mm diameter barstock. It requires internal threads on the battery tube, and is indeed "thinwall." There are 25-30 of them out there somewhere, and they tend to be "picky" about battery brand :green: . Some still have their windows/optics, others... :shrug: Mike Jordan's microconvertors haven't been available for some time, but were small enough to be used in the formfactor. 

Sorry,  (And I had the pleasure of visiting Nivelles for a couple days not too long ago!  )

Larry


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