# 6P-sized custom body project



## DrafterDan (Sep 9, 2013)

Hello all,
I was pointed over to this sub-forum, apologies for cross-posting as I can't figure out how to move a thread.

I'm working on a custom flashlight project, using 6061-T6, and have come across something worrisome. It looks to me like the body will be .02" (.5mm) thick in a couple places. At the tail, right where the threading stops, and where the gasket goes is pretty thin. I'm figuring on boring the inside to .734" (18.65mm). This won't leave much for strength. Will this be the first place the light breaks? 

DWG #1, an overall (not all dimensions shown of course)







DWG #2, a tail closeup
Grey linetype is the interior boring at .734"
Green linetype is the bottom of the threads/ gasket pocket at .755"
Dashed Green linetype is the 18650 I'm patterning this from (a Zebralight ZL631 protected)






It seems too thin. Is this an area of concern. I intend on using this/ these lights, so I'd like them tough. 
For the record, I've access to a full machine shop, everything except a radially-indexing head for the DRO CNC.

Added info: I plan on using SF and SolarForce bezels/ tails, so they'd have to be Z44-sized. There are people boring out existing SF bodies to house the 18650, so is it just assumed you will have to baby the light? Doesn't seem like a good plan to me.

Thanks for your input on my first manufacturing project!
~Daniel

**edit, changed thread name to better reflect ongoing project.


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## gadget_lover (Sep 10, 2013)

*Re: Dimensional question on 6P-sized custom body project*

You need not worry much. A short section of .020 is fairly sturdy when in a tube. 

If that were on an edge you'd have some concerns with it denting when it is dropped. In your case it is protected by being sandwiched between some thicker areas so even dropping it will not cause a dent there.

I've built a lights with several parts that were quite thin. I did the bezel on one at .015 using 6061 and was sad that it dented when dropped. The whole weight of the light was concentrated on one spot. The skirt of the tail cap was even thinner and never had a dent. I just measured the skirt of a Fenix LD20 at .023. A pelican M6 had parts as thin as .028 and the thinest I found on my L4 surefire was around .036.

Since you have a small machine shop do a dummy run and see if you can make that part fail before something else gets messed up. Chances are it will not be the weakest link. 

Oh... the biggest problem with a setup like that comes when someone buys it and thinks they can bore it out to use a slightly larger battery. All of us have 'parted' a flashlight at a groove by accident at one time or another.

Dan


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## precisionworks (Sep 10, 2013)

*Re: Dimensional question on 6P-sized custom body project*



DrafterDan said:


> It looks to me like the body will be .02" (.5mm) thick in a couple places. At the tail, right where the threading stops, and where the gasket goes is pretty thin. I'm figuring on boring the inside to .734" (18.65mm). This won't leave much for strength. Will this be the first place the light breaks?



.734" is too small to accomodate many protected 18650's - .738" covers most everything out there except the newest 3400 mAh cells & those need .744"



> There are people boring out existing SF bodies to house the 18650, so is it just assumed you will have to baby the light?



Many of my boring customers are LEO-FF-EMT & some MIL. They beat the holy crap out of all their equipment including lights - nothing like ramming the bezel of a weapon mounted light against a brick wall barricade to test durability. No failures to date.

Thin & thick are relative terms that can be best addressed by finite element analysis. Many shops that run SolidWorks have the FEA package & you'll want to run the numbers to see where your design fails. The only lights that run really thin IMO are the E-series & L-series because the O-ring OD is .752". These get a smaller bore (.728") leaving a wall thickness of .012" (about 1/4 mm). Not all 18650's will fit into this bore size but quite a few will - including 2900 & 3100 mAh AW protected cells. Again there are no failures to date.


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## DrafterDan (Sep 10, 2013)

*Re: Dimensional question on 6P-sized custom body project*

Excellent. I can toss in a few more thou to make sure various batteries will work. I'm just planning on building less than 10 for my family and a couple friends. Since I have to learn threading before I attempt on a "real" body, I'm sure I will have several dummy bodies to do testing on. 

I'll keep posting my progress, pretty sure I'll run into other questions. The metal shop is my fathers. His hobby is building sports cars like this:






~D


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## precisionworks (Sep 10, 2013)

*Re: Dimensional question on 6P-sized custom body project*

Nice wheels :thumbsup:



DrafterDan said:


> ... I have to learn threading before I attempt on a "real" body, I'm sure I will have several dummy bodies to do testing on.



Manual threading or cnc threading? CNC is nice when doing a run of 10.


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## DrafterDan (Sep 11, 2013)

*Re: Dimensional question on 6P-sized custom body project*

The mill is an old Bridgeport, although it's been thoroughly gone through and updated. It has variable speed, motor driven bed and digital readout (DRO). But it's still a basic mill, not CNC. I'm sure some photos will be posted as we move through the machining processes. 

We plan on doing some test threading this weekend.


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## gadget_lover (Sep 11, 2013)

*Re: Dimensional question on 6P-sized custom body project*

In most cases you will do a thread on a tube using a die (if it's a standard size) or single point on a lathe. The lathe can be CNC or manual. Threading on a lathe is not as difficult as it sounds. It's just a matter of following instructions and understanding terms.

If you have a CNC mill you can mill the threads too.

Daniel


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## Cavi Mike (Sep 13, 2013)

*Re: Dimensional question on 6P-sized custom body project*

The O-ring doesn't have to seat all the way into the body. Make the OD on the body larger and open up the ID of the cap to compensate. It's just rubber, it will stretch.


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## gadget_lover (Sep 13, 2013)

*Re: Dimensional question on 6P-sized custom body project*



Cavi Mike said:


> The O-ring doesn't have to seat all the way into the body. Make the OD on the body larger and open up the ID of the cap to compensate. It's just rubber, it will stretch.



There is a thread in this sub forum that deals with o-rings. A source of o-ring specifications is found in that thread. There is a definite science behind making the groove the right size and shape for the particular o-ring that you choose.

Cavi Mike: in this case he is trying to make a part that will mate to tailcaps from Surefire. This constrains the dimensions that he can work with.

Daniel


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## precisionworks (Sep 13, 2013)

*Re: Dimensional question on 6P-sized custom body project*



gadget_lover said:


> There is a definite science behind making the groove the right size and shape for the particular o-ring that you choose.


+1

Quite a few considerations ... groove OD should be about 2% greater than O-ring ID, groove width should be 1.5X O-ring cross section diameter, groove depth is determined by cross section diameter & desired compression, etc. A quick calculator here:

http://www.efunda.com/designstandards/oring/calc_oring_radial.cfm

Or you can measure a SF body & duplicate those dimensions.


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## DrafterDan (Sep 16, 2013)

*Re: Dimensional question on 6P-sized custom body project*

@ precisionworks and Gadget Lover, I'm taking the easy route and copying the 6p...
I need to wait for some inserts and other parts to show up before I can continue, so it will be awhile before I update. We did figure out how to do the 20tpi threading. It all made more sense once we figured out to switch over to the Imperial gearing! 
First cuts


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## Tiresius (Sep 17, 2013)

*Re: Dimensional question on 6P-sized custom body project*

These two are always the first to give the most reliable and unbiased information, DrafterDan. They're the ones that helped me through my machining problems.


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## Tiresius (Sep 17, 2013)

*Re: Dimensional question on 6P-sized custom body project*

I forgot to mention about cylinder wall strength. You need at least 0.5mm of untouched wall thickness. DO NOT thread with 0.5mm thickness left before actually threading. You'll end up with a thrown away project. There would be too little metal left and you're left with two results:

1.) You cut a hole through the wall.
2.) You have a bulge on the opposite side of the threaded section.

You'll have to do the math first and acquire the right thickness. Make sure you input the dept of the thread cuts AND the desired cylinder wall thickness on top of it. This is where I messed up on my first full build project.


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## DrafterDan (Sep 18, 2013)

*Re: Dimensional question on 6P-sized custom body project*

Thanks Tiresius, for both the recommendation and the tip. That does make sense, I was thinking about doing the threading last, but will do the o-ring grooves last.


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## precisionworks (Sep 18, 2013)

*Re: Dimensional question on 6P-sized custom body project*

As long as you follow 6P dimensions (with the exception of bore size) you should be OK.

Groove depth on all full sized SF lights is about .775". Your bore size leaves a wall thickness of .015" which is a lot of material IF (probably need to repeat that) IF the OD & the ID are concentric. Easiest way to achieve concentric OD/ID is to do as many ops as possible with one chucking.

Since the tail of the light is a long way from the chuck (for threading) center drill the solid stock & use a live center when threading - much less deflection that way. Finish the threads, make the O-ring cuts & then drill/bore/ream the tube.

You'll still have to figure a way to hold the nearly finished tube to thread the head & the forward part of the body will have to be taper bored to accept a drop in module but it just takes planning.


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## PCC (Sep 20, 2013)

*Re: Dimensional question on 6P-sized custom body project*



precisionworks said:


> You'll still have to figure a way to hold the nearly finished tube to thread the head & the forward part of the body will have to be taper bored to accept a drop in module but it just takes planning.


Here's an inexpensive and quick way to protect the outside of a 1" light body in the chuck. It's Schedule 40 PVC with a slit cut down one side. 






As far as the drop-in pocket is concerned, I would bore it to be a snug fit with whatever drop-in you choose. It makes it difficult or impossible to upgrade later on, though.






This light has a drop-in pocket bored specifically for this Neoseikan drop-in. It was pressed into the body so the thermal path is quite good.


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## wquiles (Sep 21, 2013)

*Re: Dimensional question on 6P-sized custom body project*



PCC said:


> Here's an inexpensive and quick way to protect the outside of a 1" light body in the chuck. It's Schedule 40 PVC with a slit cut down one side.


I use Delrin a lot for making custom fitted rings/collets/etc., but I got to admit that the PVC here was a perfect use :thumbsup:


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## precisionworks (Sep 21, 2013)

*Re: Dimensional question on 6P-sized custom body project*

My normal split collet material is 2" OD Delrin. With a nominal 1" bore the remaining sidewalls are 1/2" thick. Thicker sidewalls do a nice job distributing jaw pressure from either a 3-jaw or 4-jaw chuck & my chuck jaws are tightened as much as possible to keep the body from spinning while reaming.

Thinner material can certainly be used if a reamer isn't part of the process. Boring with a single point tool generates minimal torque reaction force but reaming forces are many times higher. Running my lathe at 100 rpm for reaming produces 157.5 lb/ft available torque & it's easy to hear the motor loading down during a typical 2-cell ream. Reamers generate a huge amount of surface contact area compared to single point boring.


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## DrafterDan (Sep 24, 2013)

*Re: Dimensional question on 6P-sized custom body project*

I know what I'll be doing this weekend, the tooling showed up.


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## precisionworks (Sep 24, 2013)

*Re: Dimensional question on 6P-sized custom body project*

The silver inserts work well for finish cuts on aluminum but they aren't meant to remove lots of material per pass. The manufacturer's website will give a maximum DOC & a max feed - stay within those for good life.


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## DrafterDan (Sep 25, 2013)

*Re: Dimensional question on 6P-sized custom body project*

Thanks for that tip, I'll look up that info. I do have some other carbide inserts and holders that I'd intended to do the "grunt work". I was just excited about getting shiny new tooling!


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## precisionworks (Sep 26, 2013)

*Re: Dimensional question on 6P-sized custom body project*



DrafterDan said:


> ... I do have some other carbide inserts and holders that I'd intended to do the "grunt work".


Good to hear that. The more pointy an insert the easier it is to break off the tip. For fine detail profiling I use the insert shown below, run it at 50 sfpm in Ti-6-4 & limit the DOC to .010" or less. Nose radius is .008" which is the smallest one I have.







Roughing gets done with a large nose radius on either a negative or neutral insert at normal titanium speed (about 150 sfpm). CNMG & SNMG shapes are both available as Aluminum Specific (polished rake face) and can sometimes be found for as little as $5 each. The small pointed insert shown in the photo is $10 & has only two cutting edges so breaking those hurts.


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## DrafterDan (Sep 28, 2013)

*Re: Dimensional question on 6P-sized custom body project*

More progress was made yesterday. I roughed out one body to get a feel for how it would go. I brought it down to a few thou of final dimensions. The next step is to break out the new fancy inserts to do the final milling and threading.


















PS: those are my father's hands, I was manning the camera!


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## Tiresius (Sep 28, 2013)

*Re: Dimensional question on 6P-sized custom body project*

You know what's the best part about making your own custom body? You have complete control over what the gut's design is. I'd go with a D26 design because it's easiest to make a drop-in for.


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## precisionworks (Sep 29, 2013)

*Re: Dimensional question on 6P-sized custom body project*

Looks good Dan.

Are you planning to knurl or groove the body? If so the time to do that is now because the body still has full support in the chuck & lots of wall thickness.


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## PhotonFanatic (Sep 29, 2013)

*Re: Dimensional question on 6P-sized custom body project*



DrafterDan said:


> More progress was made yesterday. I roughed out one body to get a feel for how it would go. I brought it down to a few thou of final dimensions. The next step is to break out the new fancy inserts to do the final milling and threading.



Can I suggest that you do not tempt Fate by using such a large overhang? There's no need to have the stock sticking out that far from the chuck.


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## precisionworks (Sep 29, 2013)

*Re: Dimensional question on 6P-sized custom body project*



PhotonFanatic said:


> Can I suggest that you do not tempt Fate by using such a large overhang? There's no need to have the stock sticking out that far from the chuck.


Great point Fred. I totally missed that.

Along the same line of thought ... is a live center being used to support the tail end? The image in post #11 shows no evidence of tailstock support:






You can get away without TS support at one to two diameters from the chuck jaws. Guessing that the round stock is 1.5" diameter, if so the maximum safe distance from the chuck jaws is 3" without TS support. Anything beyond that is an invitation for disaster ... with luck you only break tooling, without it you go to the doc & get sewn up.


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## DrafterDan (Oct 2, 2013)

*Re: Dimensional question on 6P-sized custom body project*

Updates from last night's work. The flashlight body shown above ended up being a "test piece". I learned quite a lot doing that first one, and we're already on version 2.0. I was using the live tailpiece several times on the previous one, but probably not as much as I should have. The threading and knurling we did on v1 was all done with the tail in place, and it turned out quite well! A solarforce tailcap screwed right on without issues. 
I feel very confident with the new tooling/ inserts that we can make a viable body. 






We got a late start, so didn't get as much done. Just some basic roughing out. One of the things I'm learning is economy of movement. Proper planning sure makes things easier!


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## DrafterDan (Oct 16, 2013)

*Re: Dimensional question on 6P-sized custom body project*

I haven't done anything for a while, but did manage to get some lathe time in last night. 






body is complete up to the bezel shoulder. We do need to make a couple more boring passes to clean up the insides. Then I get to try the PVC trick when we part this off and finish up the threading on the business end. It looks like I need to make six of these bodies, for family gifts. I'll either really like the process, or hate working on lathes by the time I'm done


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## precisionworks (Oct 16, 2013)

*Re: Dimensional question on 6P-sized custom body project*



DrafterDan said:


> ... I get to try the PVC trick when we part this off and finish up the threading on the business end.



I've never tried PVC pipe as I machine a dedicated split bushing for every model light that I work on. Delrin is nice but pricey, UHMW works just as well for half the cost. I make the ID identical to the body OD for a size-on-size fit & runout is normally around 0.001"

Three splits are made at 120° spacing. Two go only half way through & one is cut all the way through.


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## PCC (Oct 16, 2013)

*Re: Dimensional question on 6P-sized custom body project*

Sorry, forgot to mention that the PVC trick works if you have a four jaw independent chuck because you can center your piece using the individual adjustments. If your chuck is not independent then you're subject to possible variances in thickness of the PVC which will cause your piece to not be concentric.


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## DrafterDan (Oct 31, 2013)

*Re: Dimensional question on 6P-sized custom body project*

I can really only devote a couple hours per week, so updates have been slow. First flashlight body is complete, just need to build the LED module. I plan on working with that tonight, so maybe I'll get photos up of the complete 1st body.

Body #2 version 4 is very close to complete. Here it is during part-off





An with the Ronac tailcap fitted





Now I need to chuck it up again and refine the bezel end. We do have a split piece of PVC pipe, but we've used a boring bar on the ID to keep it as consistent as possible. With luck, I can get body #2 finished this weekend.


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## wquiles (Nov 1, 2013)

*Re: Dimensional question on 6P-sized custom body project*

Very nice work


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## tobrien (Nov 1, 2013)

*Re: Dimensional question on 6P-sized custom body project*



wquiles said:


> Very nice work



agreed, good stuff man!


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## precisionworks (Nov 2, 2013)

*Re: Dimensional question on 6P-sized custom body project*



DrafterDan said:


> ... We do have a split piece of PVC pipe, but we've used a boring bar on the ID to keep it as consistent as possible ...



After machining a couple of dozen different split bushings two details jump out ...

First turn the OD of the bushing so it's a dead nuts cylindrical shape with no ovality & no taper. Part off the cylinder.

Then chuck the cylinder on the OD & bore the ID for a size-on-size fit with the body.

The reason I start with 2" diameter Delrin or 2" diameter HDPE is so the walls will be adequately thick after boring a nominal 1.000" hole. The bushing walls are about 1/2" thick & this has worked well on every light I've bored. I've never tried making a bushing out of smaller material as the 2" OD fits easily through the bore in my chucks (both 3-jaw & 4-jaw). If the bushing is carefully machined on both OD & ID most lights will indicate .002" TIR or less in the 3-jaw & a Post-It Note or two will bring that down to well under .001" TIR. 

Just saying


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## DrafterDan (Nov 2, 2013)

*Re: Dimensional question on 6P-sized custom body project*

So HEv1 is complete. Well, maybe 99% because I'd like to polish the bezel head a bit more. I purchased several solarforce bezels, with a light blue anodizing, I think it looks better in the white. This is my father's light (his lathe, he gets the first one!), he wanted a thicker body and a cool spiral design. 

On to the photos!











LED is an XML2 @ 5K, run from an 18650, controlled by a Nanjg 105c five mode.


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## Bullzeyebill (Nov 2, 2013)

*Re: Dimensional question on 6P-sized custom body project*

Nice work. Please resize images to 800x800 pixels max. Thanks,

Bill


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## DrafterDan (Nov 4, 2013)

*Re: Dimensional question on 6P-sized custom body project*

my light, HEv2 is finished, save for installing the tritium vials in the ronac tailcap once they arrive. I'm posting smaller images now.


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## DrafterDan (Nov 27, 2013)

*Re: Dimensional question on 6P-sized custom body project*

here are the final products. We made a total of five flashlights. Thank you everyone for your grand help in this process!


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## precisionworks (Nov 28, 2013)

Those came out great. Any plans for a Ti version?


Barry Milton
Precision-Gunsmithing.com
iPhone5 voice recognition


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