# Best Flashlight Material



## Flashlight Aficionado (Apr 8, 2009)

What is the best flashlight material? You need a conductive material to let the body conduct some electricity. The material has to transfer heat efficiently. Crush and scratch resistance is always a plus. Lighter weight makes EDC easier.

No price limit. I am just asking for amusement and to gain knowledge. Let's have some fun.

Gold - great conductor, easily scratched and crushed, very heavy and a great heat conductor. Not a great flashlight material.


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## rayman (Apr 8, 2009)

Don't know what the best material for the heatsink is. But hard-anodized aluminium is really good for the body of the flashlight as it is relatively light and is really tough.

rayman


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## Marduke (Apr 8, 2009)

In the aerospace world, there is just such a material called Wishalloy. It has all the properties you desire. The price is prohibitively expensive however, to the point of being unobtainable....


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## Kestrel (Apr 8, 2009)

Beryllium (~3%) - copper alloy

~200k psi yield (~2x-3x that of 7000-series aluminum) so a very high strength-to-weight ratio
Very high electrical and thermal conductivity, considerably higher than (precipitation-hardened) 7000-series Al.
I also wanted to drop in a table I put together earlier, since rayman mentioned heatsinks:
*Thermal* Specific _Den _*“Thermal*
*conduct* HeatCap _sity _*volume”*
(W / mK) (J / gK) (g/cc)_ (J/ccK)​Aluminum *250* __0.85 ___2.7__ *2.3*
Brass..... *110* __0.38 ___8.6 __*3.2*
Copper... *400* __0.39__ 10.5__ *4.0*
Silver..... *430 *__0.23 ___9.0 __*2.1*
("thermal volume" is the heat that a fixed-size part such as a heatsink will absorb, per degree rise in temperature)


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## wadus (Apr 8, 2009)

Kestrel, how expensive would a light made of that cost for the body? Also, is it corrosion resistant at all? I know copper corrodes pretty badly; the statue of liberty is a good example of why I ask.


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## mmajunkie (Apr 8, 2009)

Marduke said:


> In the aerospace world, there is just such a material called Wishalloy. It has all the properties you desire. The price is prohibitively expensive however, to the point of being unobtainable....



Do your 7,591 other posts contribute this much?


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## Kestrel (Apr 8, 2009)

wadus said:


> Kestrel, how expensive would a light made of that cost for the body? Also, is it corrosion resistant at all? I know copper corrodes pretty badly; the statue of liberty is a good example of why I ask.


Probably pretty spendy, Be-Cu is being phased out of use due to toxicity issues related to the generation of fine Be particulates during machining.

Corrosion would be somewhat worse than pure copper due to the high distortion in the copper lattice from the Be-Cu intermetallic precipitates. However, the oxidized surfaces are pretty inert and are actually rather attractive, in a subdued sort of way.


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## Gunner12 (Apr 8, 2009)

What about multi layers? I'm thinking copper(or even silver) inner layer with coating on the very inside for chemical resistance and something and the outer layer will be something that holds heat well and the very outside will be something like Ti or Stainless steel or if the second layer is Al, good HA. I'm not sure how well the thermal transfer will work though. Contacts will be gold plated (and no contact through the threads).


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## Blindasabat (Apr 8, 2009)

It's called unobtanium. The term we use around work for the material we want to use, but doesn't exist. "What's that made of, unobtanium?"

I'll second Beryllium. But more pure, not alloyed with Copper. Lighter than aluminum & less thermal conductivity, but compared to any other material even AL & copper, it has better thermal properties relative to its density (more thermal conductivity & capacity per given mass). It is stronger than AL of the same thickness. But very expensive - $745/kg (!) . And it is a carcinogen, so coat it in something!  Don't breathe the machining dust!

From Wikipedia:


Wikipedia said:


> Beryllium has one of the highest melting points of the light metals. The modulus of elasticity of beryllium is approximately a third greater than that of steel (stiffer than steel). It has excellent thermal conductivity and is nonmagnetic.
> At standard temperature and pressures beryllium resists oxidation when exposed to air.
> Due to its stiffness, light weight, and dimensional stability over a wide temperature range (down to -240C), beryllium metal is used for lightweight structural components in the defense and aerospace industries in high-speed aircraft, missiles, space vehicles, and communication satellites. Several liquid-fueled rockets use nozzles of pure beryllium, such as the Saturn V.


"My flashlight is a missile!" :nana:

Beryllium Copper is good for a "normal"  material:
"Beryllium copper is a ductile, weldable, and machinable alloy. It is resistant to non-oxidizing acids (for example, hydrochloric acid, or carbonic acid), to plastic decomposition products, to abrasive wear and to galling. Furthermore, it can be heat-treated to improve its strength, durability, and electrical conductivity.


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## Sub_Umbra (Apr 8, 2009)

"Best" might be differemt for different types of lights. The self-lubricating qualities of brass make it nice for small pocket twisties...


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## nzbazza (Apr 8, 2009)

Flashlight Aficionado said:


> Gold - great conductor, easily scratched and crushed, very heavy and a great heat conductor. Not a great flashlight material.



Gold has some advantages:

Major bling factor
If made from 24K gold, one could easily make the battery tube larger to fit an additional cell in...

What about Al-Li alloys? When compared to more standard 2xxxx and 7xxxx Al alloys, Al-Li alloys have

• 7-10% Lower density.
• 10-15% Higher Modulus.
• Excellent fatigue and cryogenic toughness properties.
• Higher stiffness.
• Superior fatigue crack growth resistance.
• Reduced ductility
• Low fracture toughness

For Al-Li alloy 2090
Density, 2.59 g/cm3
Melting range, 560-650 degC
Elastic modulus, 76 GPa
Poisson’s ratio 0.34
Thermal conductivity at 250C, 84-92.3 W/m-k
Specific heat at 1000C, 1203 J/kg-k


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## kramer5150 (Apr 8, 2009)

Copper as mentioned above.
In a lot of the designs I review at work, if aluminum heatsinks do not provide sufficient thermal conduction we opt to spend more $$$ and go with copper.

FWIW, 316L and titanium (two very sought after boutique CPF materials) are both relatively poor thermal conductors. IIRC titanium behaves more like a thermal insulator.


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## Kestrel (Apr 8, 2009)

The thing with Aluminum-lithium, yes some of the mechanical properties are improved, but the OP was asking for good thermal conductivity as well. Al-Li has only about 50% of the thermal conductivity of 6000-series Al.


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## Marduke (Apr 8, 2009)

mmajunkie said:


> Do your 7,591 other posts contribute this much?



Swing and a miss.....


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## Marduke (Apr 8, 2009)

Kestrel said:


> The thing with Aluminum-lithium, yes it's strong enough, but the OP was asking for good thermal & electrical conductivity as well. Al-Li has only about 50% of the conductivity of 6000-series Al.



Some alloys of it are better than others. It's just harder to find published data on them due to their primary uses


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## Kestrel (Apr 8, 2009)

Marduke said:


> Some alloys of it are better than others.


Yes, it's very difficult to generalize when talking about various alloy compositions of the same element. A co-worker of mine was one of the original developers of modern Al-Li, when the issue of Lithium diffusing out of the Aluminum lattice was solved.


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## Patriot (Apr 8, 2009)

Marduke said:


> Some alloys of it are better than others. It's just harder to find published data on them due to their primary uses




Meaning weapons or aerospace....military and such? I noticed there was limited info on some of the metals discussed so far after trying to search them.


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## Marduke (Apr 8, 2009)

Patriot said:


> Meaning weapons or aerospace....military and such? I noticed there was limited info on some of the metals discussed so far after trying to search them.



If they have not yet been consumerized, and/or used for applications which could be used for military purposes, information is withheld.


Al-Li 2195 is a good example that I have a great deal of experience with.


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## Big_Ed (Apr 8, 2009)

Best can mean different things in different situations. For example, if you work outside in a cold climate, a metal flashlight might not be the best choice. A plastic or rubber one would be much more comfortable to hold. And it'll be lighter too.


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## american lockpicker (Apr 8, 2009)

I like brass and stainless steel.


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## Art Vandelay (Apr 8, 2009)

It depends. Most of the time the answer would be aluminum.

For no reason in particular, I'd like one made of titanium.


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## LukeA (Apr 8, 2009)

Marduke said:


> Swing and a miss.....



I disagree. The quoted post (with image completely irrelevant to the thread!) is informationally useless.

As for the OP, 6000 and 7000 series Aluminum alloys seem to me to be the best compromise among thermal, electrical and physical properties. I can't think of a better performing material than aluminum alloy at any price point.

That said, they all need a good coating to improve emissivity and environment resistance.


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## Marduke (Apr 8, 2009)

LukeA said:


> I disagree. The quoted post (with image completely irrelevant to the thread!) is informationally useless.



The originally quoted post had no picture. It was also quite informative in the respect that it demonstrated the "best material" for ANY device does not, and cannot ever exist.

However, that underlying meaning in the statement, obvious to most, was clearly too cerebral for others, hence the later "swing and a miss" comment. I attempted to instead post an "over your head" comment, but I could not easily find an accompanying picture.


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## Sgt. LED (Apr 8, 2009)




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## popcornpicker (Apr 9, 2009)

So then we all agree on an aluminum alloy with a Ti coating, right?


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## StarHalo (Apr 9, 2009)

I think the bigger question is if that much more thermal conductivity over what we already have will make that big a difference - we know if you put an MC-E in a 6P host, the aluminum won't be enough to sink away the heat, so if we had a hypothetical Super-6P made from Kestrel's BeCu alloy or Gunner's "Club Sandwich" multi-layers-of-everything design, would it then wick away heat so much better that the MC-E could be driven hard indefinitely? 

It just seems to me that there's only so much you can do thermally with a limited amount of an inert material before you have to move to active cooling, and a lot of our current emitter/host combos have crossed that line..


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## DM51 (Apr 9, 2009)

Unnecessary bickering aside, this is an interesting thread about materials. Kestrel, you obviously know quite a bit about alloys, and it's intersting to hear it. 

I'm moving the thread to MMM.


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## KC2IXE (Apr 9, 2009)

There isn't one "Best" material (well, except for unobtainium - and folks, it is a standard line, usually from a more Sr designer to some Jr kid, who makes a design that needs it)

Engineering is the art of "the tradeoff" Silver will give you great thermal and electrical conductivity, but will scratch/tarnish, and is somewhat expensive. Gold won't tarnish, is an OK electrical/thermal conductor, but keeps conducting. Ti is light, but is thermally poor, and will scratch. Berylium - hahahaha - yeah, that'd keep you happy for the rest of your fairly short life (Machining Be is done in sealed hoods). BeCu has it's good points. Carbon fibre - nice, light strong, but doesn't conduct, and is brittle

If you wanted to go exotic - it might be something like:
Carbon fibre Battery tube, with 7075 (or even 6061 or Ti) inserts on the ends for threads, a BeCu strip on the inside to conduct the electrons. Gold plate on the contact points on the points where the strips connect on both ends, a Al or Ti tail cap, the head being a sandwich of say Al and CU, or even Ti and CU, with the Cu heatsink exposed out to the edge of the head - or maybe instead of copper, Nickle Silver (actually a Cu alloy that has the advantage of haning it's tarnish being electrically conductive) - or, how about, Cu, and have the outside Gold Plated (or maybe Rhodium) to prevent tarnish? Oh - I know - PVD Diamond coat (Diamond actually is a great thermal conductor)

Is Manufacturing this beast going to be EASY? NO. Cheap, Hahahahaha.

Asking what the "best" material to make a flashlight out of is like saying "what is the best material to make a car out of?" - different parts want to be made from different things


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## Blindasabat (Apr 9, 2009)

It is not necessarily true than an Auminum MC-E/P7 6P will not work. Material is not everything - design can make a big impact. Often with adequate finning, AL can transfer the heat away via convection. I did some calculations on that in a thread a month or so ago when I compared AL to copper. Conductivity made very little difference as long as you could move the heat out to the body of the FL & allow it to dissipate via convection. In that case AL won by being lighter & lower cost than copper for only a degree or two difference at the LED. A properly designed 6P sized light with adequate finning or thermal path to the holder's hand would do better than a stock 6P made of the same AL alloy. The stock "drop-in" design of the 6P is the biggest problem. Make a finned head with the LED AA to the head itself and thermal dissipation will increase significantly.


StarHalo said:


> ...we know if you put an MC-E in a 6P host, the aluminum won't be enough to sink away the heat...


The stock "drop-in" design of the 6P is the biggest problem. Make a finned head with the LED AA to the head itself and thermal dissipation will increase significantly. 
Even though this thread is about material, I just want people to know that proper thermal path design is more significant and will make a bigger difference than changing material alone. Turboferret put a MC-E Malkoff in a redesigned AL headlight designed for LED drop-ins and it runs 3.5-4 amps with no problem for long times. And that actually has less aluminum because it is missing a battery tube, but it has some (minimal) finning.

Replacing the 6P head with a KL3, will also be far more efficient as the KL3 was designed for an LED while the 6P was not. IIRC some people have even put MC-E & P7 into KL3 with no problem, and even smaller KL1/KX1 (smaller than a 6P head) with little problem if not driven too hard.


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## precisionworks (Apr 9, 2009)

> I noticed there was limited info on some of the metals discussed so far after trying to search them.



The best source for commercially available metals information (IMO) is Metals Handbook Desk Edition. If you have a fat wallet & need the newest information, buy the most recent 2nd Edition for $286 (ISBN 0871706547). Many users, self included, find the 1st Edition very useful, and a bargain for around $50 if you shop the online book sellers (Alibris, AbeBooks, etc.). Look for ISBN 087170188x.

Other than Machinery's Handbook, nothing else in the shop is used more often. The information from a Google search is so limited, compared to the information in this book.



> What is the best flashlight material?


The larger volume makers, like SureFire, buy their material in near net shape extrusions, which lowers both materials cost & machining cycle times. It wouldn't surprise me to see them use a PM (powdered metal) aluminum alloy, as PM can be custom blended to achieve almost any desired physical, mechanical & electrical property ... within the limits of the alloy itself. Alcan 76 is the PM version of Type 7075, both having high strength & hardness.


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## Blindasabat (Apr 9, 2009)

Even though brass does not have thermal conductivity as high as AL or Copper, Malkoff makes a good drop-in with it because of superior thermal design (patent pending he says on his site). A Malkoff might run two degrees cooler made from Copper, but would cost more... like KC2IXE said, engineering is an educated & reasoned balancing of tradeoffs.


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## Anglepoise (Apr 9, 2009)

For me it is no contest. Ti is the perfect material ( forgetting that it is very hard on the tooling used to machine it.)

It is strong, tough, and a thin tube holds up well. It looks great with a gray sheen and does not corrode (Aluminum ) or tarnish (Brass ). If after extensive use, it can be made to look like new again with a few minutes spent with a 'Scotchbrite pad'. It does NOT need any type of coating. 

It's electrical properties are good as its 'oxide' is conductive. And the lack of heat transmission as a problem has become a non issue for most of the builders. Weight ?. As flashlights are thin tubes, weight becomes less of an issue with Ti. Everyone at some stage in their CPF membership should own a Ti light with a single light weigh lithium rechargeable CR123a battery.
The ultimate EDC.


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## precisionworks (Apr 9, 2009)

> It (Ti) does NOT need any type of coating.


Threaded, moving connections, like a twist head or a twist tail cap, are the one area that can benefit from a coating. Ti on Ti galling is well documented ... one website says this:

_When titanium slides against titanium it tends to gall or stick more so than any other metal combination. Similarly, titanium to titanium parts in threaded combination “cold weld” making disassembly impossible without destroying the parts. In order to prevent this, typically dry film lubricants are applied over suitably prepared titanium (i.e. either anodized or conversion coated)._ 

http://www.finishing.com/Library/titanium.html


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## Marduke (Apr 9, 2009)

precisionworks said:


> The best source for commercially available metals information (IMO) is Metals Handbook Desk Edition. If you have a fat wallet & need the newest information, buy the most recent 2nd Edition for $286 (ISBN 0871706547). Many users, self included, find the 1st Edition very useful, and a bargain for around $50 if you shop the online book sellers (Alibris, AbeBooks, etc.). Look for ISBN 087170188x.
> 
> Other than Machinery's Handbook, nothing else in the shop is used more often. The information from a Google search is so limited, compared to the information in this book.



MIL-HDBK-5J is an excellent source for metals information. It has been superseded by MMPDS04, but 5J is now available for free. 

For a quick search MatWeb is also a useful source, but you must take the numbers with a grain of salt since they are usually commercial "typical" values and not statistical design allowables.


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## Kestrel (Apr 9, 2009)

Blindasabat said:


> Even though brass does not have thermal conductivity as high as AL or Copper, Malkoff makes a good drop-in with it because of superior thermal design (patent pending he says on his site). A Malkoff might run two degrees cooler made from Copper, but would cost more...


BTW I asked Gene about the possibility of using an aluminum heatsink / drop-in body, but he says that he can't get the soldering good enough to get a good thermal path.


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## Mick (Apr 9, 2009)

Aluminum alloy 7068 is a good choice for high strength as it is about 30% stronger than 7075. It does not form well so would be tough to knurl. 
Here is a nice aluminum properties chart for quick reference. Note you can get 7068 from McM-Carr. And check 6020 for free machining.
http://www.mcmaster.com/#about-aluminum/=1ddc25


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## tino_ale (Apr 10, 2009)

I have yet to see any serious thermal study which conclusion is that Aluminium is not good enough in a flashlight, as a heatsink. Taking the heat from the flashlight to it's environment is much more of a limitation than taking the heat away from the LED to the rest of the body.

About Ti galling, I have never experienced or heard about it on flashlights as long as you keep the threads at least a little lubed.

I vote for Ti


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