# Wouldn't you like to see other Al. Alloys than 6061?



## tino_ale (Oct 10, 2007)

Hi all,

As far as I know, most of the aluminium machined flashlights are made from 6061 alloy... sometimes 6061-T6 which is heat treated.

While I totally understand this choice for low/middle priced flashlights, I am sometimes surprised that higher end models are not made from something more solid.

Expensive models and/or expensive custom torches are most of the time 6061 alloy too. You get 6061 T-6 if you're lucky. Don't get me wrong, 6061-T6 has good properties, but it's certainly not the best you can get. But when I see flashlights with to-be-released led bins, super-hyper-efficient drivers, 2mm thick (or more) AR coated sapphire glass, top notch o-rings, silver coated springs... in the middle of all these refinements well I feel that 6061 alloy, even T6, is kind of at the low end of the material choice. For example, I'm surprised to see that ARCmania $800 SF V, a zero-compromise high end and refined limited model, is machined from 6061-T6 only. Just an example.

You can go for titanium, but the offering is very limited, and prices are so much higher. Titanium has it's niche.

I would like to see something in between. It's perfectly doable with 7075-T6 alloy for example. It is something like 40% higher in tensile and yield strenght compared to 6061-T6. 300% and 700% higher if you compare to simple 6061. Upgrading from 6061-T6 to 7075-T6 would be a significant change in terms of dings/scratch/bend/breakage resistance.

I think the Tiablos are made from 7075 alloy, but I don't even know if there are flashlights out there that are made from 7075-T6. 7075 is actually a little less strong than 6061-T6.

So... I am the only one here?? I have that feeling that people are extremely picky about led bins (a P4 WC cree is kinda outdated as of today...), reflectors, glass and many other things but not the alloy used. Why? Manufacturer advertise over and over that alloy used is "aerospace aluminium"... that is 6061. Do people think when they read "aerospace" it's the very best you can get?

Thanks for your thoughts.
Cheers


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## scott.cr (Oct 10, 2007)

When a manufacturer chooses the material, it's choosing the set of compromises that suits them best; let's go with your example of a 7000 series aluminum over a 6000. The 7000 will be at a disadvantage for a rough-use light because it cannot undergo as much deformation as a 6000. Once you pass the elastic limit of the metal, its strength quickly and severely diminishes. Then there's thread gall and wear, ability to take a finish (7000 is difficult to finish unless it's a plated or spray-on finish). And of course, it takes longer to machine and thread 6000/7000 aluminums over, say, 2000 aluminums.

Look at Surefire's infamous "bulletproof 6P" ad. I'm sure a speeding bullet would have exceeded the elastic limit of a 7000 series aluminum as used in a flashlight, and the police officer carrying it may not have gotten back up to resume the fight. The (what I think is) 2011 Surefire uses gains in toughness what the 6 and 7000s have in tensile strength.

Once you look at a flashlight as a *system* that will see non-textbook use, its design considerations become a lot more than "which material in my bluebook has the highest tensile strength?"


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## Buck91 (Oct 10, 2007)

6061 and its variants has to be fairly sturdy as Trek uses it a lot for bicycle parts/frames...


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## Flash_Gordon (Oct 10, 2007)

I guess it somewhat depends on how much more you want your lights to cost with no real gain in quality, durability or utility.

Harder material requires more expensive and shorter lived machine tools. This cost will pass directly to the price of the light.

As scott.cr pointed out, there are added disadvantages. 7000 series aluminum is more brittle and might be more inclined to break rather than distort unless it is originally machined thicker and heavier.

Maybe more importantly to most of us, the harder aluminums to not take finish nearly as well. 6000 series aluminum are much easier to anodize and give us more choices in color.

7000 series aluminum is better suited for some applications but not necessarily for flashlights. It could just be over engineering without any gain.

Mark


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## Marduke (Oct 10, 2007)

For those of you who would like to know:

6061-T6 specs
7075-T6 specs

6061-T6 is slightly more fracture resistant/less brittle, but 7075-T6 is superior is almost every other way. Cost is another matter altogether...


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## tvodrd (Oct 10, 2007)

7075 T6/651 hard anodizes just fine, and the added strength helps reduce thread wear, especially with fine threads like my avatar.

Larry


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## tino_ale (Oct 11, 2007)

scott.cr said:


> The 7000 will be at a disadvantage for a rough-use light because it cannot undergo as much deformation as a 6000.


Unless some experts could confirm, I can't see how we could give a definite answer to the question : what is more important for "rough" use. Elasticity, tensile strentgh or yiels strength? As for dings, scratchs, thread wear, blemishes or other consequences of dropping a flashlight on concrete, I would intuitively say elasticity is not in play that much. I would like to do some tests about this but unfortunately I don't have the mean to do it.


Buck91 said:


> 6061 and its variants has to be fairly sturdy as Trek uses it a lot for bicycle parts/frames...


Which doesn't prove anything about the fact that 7075-T6 would or would not be superior for flashlight use. Bicycle frames are tubular structures, an entirely different subject. As I said 6061-T6 has good properties, the question is more can't mfgers/custom builders do better?


Flash_Gordon said:


> I guess it somewhat depends on how much more you want your lights to cost with no real gain in quality, durability or utility.


How are you so sure that there would not be any gain in real life? People want nothing else than HA-III now, there is a reason. They want durability against scratches and other blemishes. Don't you think 7075-T6 would be much better in that regard?


Flash_Gordon said:


> 7000 series aluminum is better suited for some applications but not necessarily for flashlights. It could just be over engineering without any gain.


I think the idea that 6061-T6 aluminium is enough for a flashlight is totally acceptable. I do think "it's enough", after all a scratched/dinged/scratched/dinged flashlight can still fullfill it's purpose of illumination tool. But I don't think it is the best. But look at most of high-end/custom flashlights. Can you say they are not over engineered already? Most of them are advertised as "no-compromise", "ultimate", or "only the best for our customers" etc. In that regard, I'm surprised how we stick to 6061 that much.

The fact that the gain from 6061-T6 to 7075-T6 is not *needed* doesn't mean it's not there. High end flashlight often implement features which brings a gain that is not "needded", but because it's a no-compromise model, it's there.

I really wonder if the slick name "aerospace aluminium" given to a pretty soft alloy after all doesn't contribute to the fact that people think they get the best out there. I personnally find that my Al flashlights are too easily and too deeply damaged from a simple drop on the floor, even from a slight smack on a hard edge and so on. Things that happend often in everyday life.

Typically, I'd just like to see something between 6061-T6 and titanium in the flashlight offer. I'm surprised it looks like there is no demand for it, while anything that is not HA-III just won't sell (talking about high end models remember).


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## Marduke (Oct 11, 2007)

I have yet to see a milled aluminum flashlight split in half from overstress. The 7075-T6 would not scratch or dent as easily, but that's what a good HA-III coating is for. Also, you would be less likely to strip the threads with 7075-T6. Either way, unless you are using the light as a hammer, the body with outlast both you and the electronics inside.


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## Patriot (Oct 11, 2007)

Clearly the 7075 T-6 is superior in almost every area. My guess is that it's an issue of cost and availability. In the next few years we may see 7075 T-6 more frequently used in construction for our hobie. By then we will probably be asking why our lights aren't made from Weldalite 49-T8 or Kobe's new alloy. There is always a lag between what cutting edge industry is using and what is commonly available to the consumer.


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## scott.cr (Oct 11, 2007)

My vote is for pure heat-treated unobtanium.


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## elgarak (Oct 11, 2007)

Let's not forget that manufacturers have to machine it. A slight improvement in mechanical properties could result in huge increase in cost for the machining of large numbers of light, without much payoff for the end user (as already pointed out).


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## Marduke (Oct 11, 2007)

scott.cr said:


> My vote is for pure heat-treated unobtanium.



+1, or adamantium :twothumbs


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## yellow (Oct 11, 2007)

glad to see there is _always_ someone more crazed than oneself.
I'm a flashoholic, but I think I might possibly be cured
- You are lost
:nana:


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## SCEMan (Oct 11, 2007)

I'd actually like to see flashlights with synthetic contact areas (non heat dissapating) to prevent marring, & scratching. It seems like my 6061-T6 flashlights are hard enough to damage about everything I accidently hit with them.


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## DM51 (Oct 12, 2007)

Very interesting thread, even for someone like me with little knowledge of metallurgy.

EDIT: Maybe it should be in the "Materials/Mechanical/Machining" section?


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## tino_ale (Oct 12, 2007)

I've just noticed the Gotham is machined from 7075-T6 alloy, the front bezel ring being Grade 5 Ti.

http://www.lighthound.com/index.asp?PageAction=VIEWPROD&ProdID=2901


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## sysadmn (Oct 12, 2007)

Marduke said:


> +1, or adamantium :twothumbs


 
I probably shouldn't mention this until the patents are filed, but I'm working on a few projects.

The first is a light made from an alloy of unobtanium and upsydaisium. I'm using it to make a light you can never buy, and never find if you do own one.

The second is a light made of heat-treated alloyed adamantium and upsydaisium. It flies around and kicks bad guys' butts!


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## mudman cj (Oct 12, 2007)

elgarak said:


> Let's not forget that manufacturers have to machine it. A slight improvement in mechanical properties could result in huge increase in cost for the machining of large numbers of light, without much payoff for the end user (as already pointed out).



The data sheets on Matweb indicate a machinability index of 50% for 6061-T6 and 70% for 7075-T6. This seems to indicate that 7075-T6 is easier to machine than 6061-T6.

If 7075 is heat treated to temper T73 instead of T6, then the ductility is comparable to 6061-T6, which will of course improve impact resistance. Corrosion resistance is also improved while retaining increases in strength and hardness.


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## tvodrd (Oct 12, 2007)

6061 T0 IMO, is a little "gummy" to machine- gives long continuous chips, which tend to wind-up on your workpiece. The T6 condition is a little better. 7075 T6 chips tend to break up and not clog things. I'll leave out things like cutter/chip breaker geometry, but at the end of the day, it's _easier_ to machine!

Larry


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## tino_ale (Oct 13, 2007)

For large manufacturers, even if "easier" to machine it may be more costy due to cutting tools requirements/wear. But for custom made or limited runs and offerings, it doesn't sound like an issue (some specialist could confirm).

A 7075-T6 D-cell mag with HA-III would be awesome. Unfortunately, nothing sound more unlikely than this considering Mag ability (or will or strategy) to evolve.


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## PEU (Oct 13, 2007)

For annodized flashlights the best choices are 6xxx and 7xxx aluminium series, others don't annodize well according to the anno shop I use.

Then there is the price factor, 6061 or 6262 (the one I used for my last run) cost 1/2 of the same size 7075 and for a flashlight that wont be used as a hammer  IMHO there is no real need to go for the expensive alloy...

There are many ways one can innovate in the art of flashlight design to just rely on the metal choice to be original 


Pablo


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## Cuso (Oct 13, 2007)

It may be that most flashaholics just dont care about what type of aluminums are used in the lights... Its either titanium or aluminum, and the "flavors" for aluminum being HAII , HAIII, or bare. Now if we talk about knifes....


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## gadget_lover (Oct 14, 2007)

6061 is ok, but I find it dents pretty easily. My first home made light was 6061-t6. The bezel was really thin (.015) and it deformed the first time I dropped it. That really burned me up.

I made my current edc from 2011. It's been my edc for about two years now. It's been dropped a few times and although it's sustained a few shallow scratches the aluminum has not dented. This is important since I have sections of the tailcap that are about .010 thick with a .002 gap between tailcap and body. Any deformation and it would bind.

2011 is REALLY nice to machine. I get good clean chips with agressive feed. The finish almost looks polished. 

Since my EDC is bare aluminum the scratches barely show. From 2 foot away they are invisible. 2011 can be anodized, but I heard that the other metals in the alloy causes it to come out blotchy. This probably could be disguised by "splash anodizing". 

I guess all I'm saying is that 2011 makes for nice bare aluminum lights.

Daniel


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## tino_ale (Oct 14, 2007)

It sounds true, this is precisely what surprises me a bit :thinking:


Cuso said:


> It may be that most flashaholics just dont care about what type of aluminums are used in the lights... Its either titanium or aluminum, and the "flavors" for aluminum being HAII , HAIII, or bare.


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## Anglepoise (Oct 14, 2007)

Very interesting thread tino. The last flashlight I machined was made out of 7075 T6. I selected this grade because I knew before I started that I was going to have very thin side walls due to my design restrictions. I was very happy with machining 7075 T6.
I suspect in the world of manufacturing every penny counts and unless one grade is very superior to another, the cost factor will be the decider.


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## dcjs (Oct 14, 2007)

tino_ale said:


> It sounds true, this is precisely what surprises me a bit :thinking:



Doesn't surprise me anymore, most people here aren't engineers, if they think that they have "the best", it gives them that warm and fuzzy feeling they are after. This only applies to subjects that are genaraly discussed and agreed upon as being "important" though, if somethin isn't visible and /or easy to understand, it may not manage to make it on the "cool factor"-list that everyone goes through when judgeing a light. 

This reminds me of knife steels, people are happy as a pig in sh*t when they have the "top flavour of the season" steel alloy that everyone is rambling about right now, but they don't care wheter this particular steel is really well-suited for the specific application, let alone about careful heat treatment etc. 

Let's face it, most decisions by hobbyists are not taken with an educated background, so it is oftentimes hard to convince people of something that has advantages but lacks the "cool factor". 

If someone marketed 7075-T6 as "Tougher than aerospace grade aluminum!", they might just have a chance.


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## Bogus1 (Oct 14, 2007)

Please correct me if I'm wrong, but hasn't one of the main reasons we've used 6061 been due to heat dissipation? In many LED lights heatsinking was and is still of primary concern.


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## tino_ale (Oct 15, 2007)

While 7075-T6 has a slightly lower thermal conductivity than 6061-T6, it is a lot better than titanium and should not be a problem at all.


Bogus1 said:


> Please correct me if I'm wrong, but hasn't one of the main reasons we've used 6061 been due to heat dissipation? In many LED lights heatsinking was and is still of primary concern.


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## sysadmn (Oct 15, 2007)

dcjs said:


> If someone marketed 7075-T6 as "Tougher than aerospace grade aluminum!", they might just have a chance.


 
Quick, get the trademark for "7075: Outer Space Grade Aluminum!"


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## Bogus1 (Oct 15, 2007)

tino_ale,

Well that all depends on how hard you are driving your LEDs on whether Ti works. 

You seem invested in 7075 as an option and I agree with your points and the points of those who know more than I do. However 6061 doesn't just have better thermal properties, it also has better electrical conductivity and better corrosion resistance. These are key features in flashlights. Certainly tensile strength is also a key feature as you have pointed out.

At TnC I've discussed with Chris using 7075 and we are fine with it if that's what customers want. Yes, it's more expensive but that expense IMO is justified. However there hasn't been a demand, as most just see aluminum as aluminum and go to Ti for durability. Personally I like my lights to weigh as little as possible and still hold up so 7075 is a good alternative IMO. At the same time to understand why 6061 has been and sometimes will remain the alloy of choice I think is also important. It's all a balancing act of priorities and applications. 

Is the added strength of 7075 worth less heat sinking, more corrosion, more electrical resistance, and perhaps more difficulty anodizing worth it? It might just be, once again depending on the customer and the uses of the light. We intend to put this question to our buyers in our future interest threads so thanks for raising the question.


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## Ron Schroeder (Oct 15, 2007)

I like 2024 alloys. It threads better than 6061 and I think the "off the lathe" finish is much better. I have made a few flashlights from it but I don't know how it will take a HAIII finish.


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## mudman cj (Oct 15, 2007)

7075-T73 actually has the same thermal conductivity as 6061-T6 at 100F. 

If you were to temper 7075 to the T6 condition though, it would exhibit about a 15% decrease in thermal conductivity. This data is from Mil-HDBK-5.

I have not yet found data for electrical conductivity, but my studies in solid state physics have taught me that they tend to go hand in hand.


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## tino_ale (Oct 15, 2007)

I would actually be interrested in some real world data about our flashlight's loss of runtime due to it's alloy electrical resistance. Shouldn't it be negligible?


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## mudman cj (Oct 15, 2007)

I found some data at the end of the work day (after hours of course) for electrical conductivity, and I will check it tomorrow against what Matweb has. They list 5.15E-6 Ohm*cm for 7075-T6, 4.3E-6 for 7075-T73, and 3.99E-6 for 6061-T6.

Assuming a cross sectional area of 1 cm^2 for a typical small light body, this gives a resistance of (3.99E-6)*(Length in cm)/1. Power lost is then I^2*R or not much larger than R for most lights since current is rarely greater than 1 amp in small lights. The results are on the order of 0.1 mW. For reference, a 5mm LED running at 20 mA and 3.2V consumes 64 mW. Therefore IMO there's really no need to be concerned about an 8% or even a 29% increase in resistivity going from 6061-T6 to 7075-T73 or 7075-T6 respectively.


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## Data (Oct 15, 2007)

I made the 005 in both 6061 and 7075. I only use T6.

If I handed you quality anodized flashlights made with 6061-T6 and another identical flashlight made with 7075-T6, you would not know the difference. If you dropped both lights on the concrete it will chip the ano and dent the surface on both of them! 

7075 does not add much to an anodized flashlight body because most bodies do not need to have a super strong strength to weight ratio like an aerospace vehicle frame does. But the cost factor is through the roof unless the light is tiny like the draco or wee.


6061 is more economical for making most flashlight bodies for several reasons:

1) the material costs less, way less.

2) It is available and so is less likely to disrupt the production cycle. This equates to lower cost. Just two years ago it was nearly imposable to get 7075. And today it is still difficult.

3) machining costs are lower because tools last longer and can cut deeper. 7075 is a harder metal and requires shallower (lower chip load) cutting to achieve the same finish and the harder 7075 will take the edge off carbide tooling quicker. 

4) more anodizing shops understand 6061, this equates to better finishes and reduced costs.

It is not just the additional cost of the material. There are many factors that go into the cost equation. 

6061 makes a better flashlight for the money.



Cheers
Dave


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## PEU (Oct 15, 2007)

Ron Schroeder said:


> I like 2024 alloys. It threads better than 6061 and I think the "off the lathe" finish is much better. I have made a few flashlights from it but I don't know how it will take a HAIII finish.



Before my 1st flashlight run I knew little to none about aluminum alloys, so I purchased bars just by the size I needed. 
When I started making samples for HA3 they consistently came out bad, meaning, the color was ok, but they weren't scratchproof.
The shop owner after the 3rd try asked me about the material, and my stupid reply was: aluminium 
Next test was done with proper 6061 (or 6262 I dont recall) and the HA3 passed the xacto knife test with honors 

The problem, as you may guessed, was the alloy 2xxx series don't hard anodize well, but they are great for machining, thats why when I told the seller the rods were for my lathe they always gave me 2xxx (is called Camplo, a local trademark)


Pablo


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## tino_ale (Oct 16, 2007)

Data said:


> If you dropped both lights on the concrete it will chip the ano and dent the surface on both of them!


That's an interresting yet surprising statement. I wouldn't expect the 7075-T6 to be intact, but at least wouldn't the dent or scatches be noticably deeper in the 6061 body? This is confusing coz it would mean yield and tensile strenght have limited to no impact at all on how a flashlight will be affected (granted, it can be only aethetic) by a drop on concrete or hard surface.



Data said:


> But the cost factor is through the roof unless the light is tiny like the draco or wee.


I was not aware price of the 7075-T6 is that much superior to the 6061-T6 price. In high end and/custom aluminium torches, I though the cost of the raw material was not much of a concern, seems that I was wrong.

I understand what you are pointing out and think it perfectly makes sense.

That said : your point about cost of the raw material and machining could be easilly applied on titanium too. I guess they would all apply, starting from the cost of the raw material, which everyone know it is very high. Still, there is an offer and a demand for titanium, eventhough titanium *has* some significant drawback compared to Al (thermal conductivity, weigth to start with). Which means there is a demand for torches that are not necessary "best bang for the bucks" and no-one, or at least not many, question the fact that most of the people who buy a titanium flashlight have any need for what it brings over aluminium. There is a passion factor that make most of us buy titanium model without any hard justification. I don't think we should be ashamed of it, heck we are flashaholics :duh2:. We are ready to pay more for something that will have some advantages over standard aluminium that we might not even need for real.

So my point is : why wouldn't this apply to higher end aluminium alloy too? Why does it seem to be a problem that we don't really need what 7075 brings over 6061, but it's not for titanium? The advantages of titanium over Al is worth the $$ (eventhough vast mojority doesn't need them) but the advantages of higher end Al alloy over standard 6061 does not?

Of course, if a more expensive aluminium alloy does not bring anything in real life (like you say in my first quote) there would be no point of dealing with the extra hassle. I just have some difficulty to understand WHY it would not make any difference (I'm really not educated that much on mechanical stuff).


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## Ron Schroeder (Oct 16, 2007)

mudman cj said:


> 7075-T73 actually has the same thermal conductivity as 6061-T6 at 100F.
> 
> If you were to temper 7075 to the T6 condition though, it would exhibit about a 15% decrease in thermal conductivity. This data is from Mil-HDBK-5.
> 
> I have not yet found data for electrical conductivity, but my studies in solid state physics have taught me that they tend to go hand in hand.



Electrical and thermal conductivity don't go hand in hand.

For example, diamond is a great electrical insulator but is probably the most thermally conductive solid.


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## mudman cj (Oct 16, 2007)

Of course they don't in all cases, or else we couldn't have devices that make use of the Seebeck or Peltier effects. I was just making a generalization about some materials of which metals such as this are members. The reason they go hand in hand in cases like this is because both must be conducted through the crystal lattice and both are affected by atomic bond characteristics and lattice discontinuities. If you want to continue this discussion I suggest PM since this is OT.


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## Data (Oct 16, 2007)

tino_ale said:


> That's an interresting yet surprising statement. I wouldn't expect the 7075-T6 to be intact, but at least wouldn't the dent or scatches be noticably deeper in the 6061 body? This is confusing coz it would mean yield and tensile strenght have limited to no impact at all on how a flashlight will be affected (granted, it can be only aethetic) by a drop on concrete or hard surface.
> 
> 
> I was not aware price of the 7075-T6 is that much superior to the 6061-T6 price. In high end and/custom aluminium torches, I though the cost of the raw material was not much of a concern, seems that I was wrong.
> ...



I think your response is spot on. I would only say that titanium brings something very real, and that is, it gives an all metal finish that can be very beautiful and much lighter than steel. It can also be polished and blemishes can be repaired. I love the shiny metal look in a flashlight.



Cheers
Dave


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## zelda (Oct 16, 2007)

7075 T6 is nice for cuting with very little or without liquids. 
The sureface with slow feed shimmers with nice colors.

Price in Switzerland is around 26$/Kg.

zelda


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## mudman cj (Oct 16, 2007)

I was told by a friend at work that the price of 7075 is about twice that of 6061, but that probably only applies to the T6 condition. Manufacturers typically age to the T6 condition and therefore charge for an additional treatment to age the extra time to achieve T73.

Anyway, I was wondering if that price ratio is about what you guys have seen purchasing for small projects instead of for industrial applications.


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## Ron Schroeder (Oct 17, 2007)

I usually get small pieces from http://www.mcmaster.com/ They sell in 1 foot lengths.


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## tnuckels (Oct 21, 2007)

In a previous lifetime I worked at a scrapyard, and learned to classify the most common aluminum alloys, based mostly on look, feel, use, how it was made (cast, extruded, etc.), and even on its filings. The 4 that I still recall were 2024, 3003, 6061 & 7075. My recollection of each follows:
2024 – springy, used a lot in aircraft body panels
3003 – soft and shiny, used when looks mattered more than durability, like cheap lawn furniture
6061 – stronger and weldable, thus its use to build bike frames, used for heavier shapes
7075 – strongest & ridged, if a bit brittle, used for structural members and more delicate shapes

Knowing these “attributes” are not very accurate, look here for more information from the manufacturer: http://www.alcoa.com/gcfp/en/product_browse.asp, and here, for a product selector: http://www.alcoa.com/gcfp/en/alloy_selector.asp.

It seems that most flashlight literature I’ve read indicates 6061 or quotes the generic use of aircraft or aerospace aluminum in their product. To achieve the smallest, strongest light possible, I can only hope that the manufacturers have gone through the tedious exercise of prototyping their body tubes in different alloys and then testing for durability characteristics, and are not simply buying what everyone else is buying.

When I hear that 7075 costs twice as much as 6061 as justification for its prevalence I can only frame this argument in terms of buying a new roof for your house, where the good looking 50yr shingles cost 2x the ugly 30yr ones, but represent a relatively small portion of the overall bill. Everything is a tradeoff. I just hope that I’m being presented with the best options available so I can pick the ones that best suit my needs.


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## gadget_lover (Oct 21, 2007)

At the local dealer it's $3 a pound no matter what I buy. 
6061? $3
7075? $3
2024? $3

I learned the hard way that a 3 foot section of 3 inch diameter 6061 weighs a LOT more than the same piece in 1 inch. I needed to buy another $10 worth of metal to meet their minimum order so I grabbed the big piece. It doubled my order. 

Daniel


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## Tritium (Oct 22, 2007)

My requirements in a use flashlight metal.
At least as tough as a Mag Light. 
Don't care beyond that. Its a tool.

My requirements in a knife blade metal.
It Sharpens well and holds an edge through normal use.
Don't care beyond that. Its a tool also.

Now collector items are a totally different story.
Anything goes.

Thurmond


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## Ron Schroeder (Oct 23, 2007)

I just machined some parts for a non-flashlight project out of both 6061 and 2024. The 2024 sure was a lot easier to get clean smooth deep holes and the external finish was a lot nicer with slow feeds.

While I was doing the machining, I was thinking that the 2024 may not knurl as well. Has anybody tried knurling 2024 or a 7000 alloy?

A glass bead finish on 2024 looked good.


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## tvodrd (Oct 23, 2007)

2024T4 should knurl as well as 6061T6. My only beef with the 2XXX alloys is poor weldability and anodizability. 

Larry


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## tnuckels (Oct 24, 2007)

There is an interesting, and perhaps telling, chart on several of the Alcoa alloy PDF sheets like this one: http://www.alcoa.com/gcfp/catalog/pdf/alcoa_alloy_2024.pdf, second page, about ½ way down, entitled: *Comparative Characteristics of Related Alloys/Tempers*. Granted, these are not all the relevant criteria you might consider when choosing the right alloy for your application, but it hits several of the top contenders and it would appear that 6061 is the overall champ, except regarding machinability, of all things. 

Isn’t knurling accomplished by impressing (formability on the chart?) the pattern into the blank surface using high pressure? Again 6061 leads the pack.

I never know exactly how to take corporate produced slicks/PDFs like these from Alcoa … sorta’ strikes me like lumen ratings from light manufacturers. However, given that they seem perfectly willing to rank their products poorly in several key areas, it might lend credence to their more glowing assessments in others … unless of course they’re just pushing a more profitable product.

Ssaaay little boy … wana’ buy a kilo of 6061? :huh:


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## Elmie (Jul 9, 2008)

*7075 vs. 6061 Aluminum*

I'll apologize in advance if this has been covered already. I tried a search but couldn't find anything specific to this.

What is the big deal with 7075? Certain individuals seem to be overly obsessed with lights being made out of 7075. I've never managed to crush or bend my existing 6061 lights and quite frankly I don't really care as long as it isn't weak like a M*g. 

If the light was being used as a tool like a screw driver then I could see why it would need to be made out of a harder alloy. But a flashlight is designed to shine light and of course have some robustness to it as well. So is 7075 really necessary for a flashlight?


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## half-watt (Jul 9, 2008)

*Re: 7075 vs. 6061 Aluminum*



Elmie said:


> ...So is 7075 really necessary for a flashlight?



maybe the right ans. is that it depends upon the particular light and expected applications - true professional use vs. collectors, for instance.

keep in mind that the temper may vary even within the particular alloy. just in case anyone is unaware, Al alloys are numbered into series, and often mentioned with a "dash number", e.g. 6061-T6, or 7075-T6 (there are other "numbered" alloys and tempers as well). so, not all 6061 is the same, nor all 7075. one needs to consider the temper as well. higher temper numbers can increase the tensile strength and yield strength of the alloy considerably - up to at least 2x greater and maybe more, but i'm forgettin' precisely how much.

one possible advantage could be in the area of wall thickness (and weight) of 7075 vs. 6061. 7075 having more than 50% greater (actually up to nearly 2x, IIRC) tensile strength and yield strength than 6061 might allow a design to be lighter and have thinner walls, yet resist yielding better than a similar design using 6061.

i'll leave it to any material scientists (which i'm not) to explain more.


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## DM51 (Jul 9, 2008)

*Re: 7075 vs. 6061 Aluminum*

I'll move this to MMM, where it will receive expert attention.


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## Elmie (Jul 9, 2008)

*Re: 7075 vs. 6061 Aluminum*

I could see why different designs would require a stronger alloy. Like the D10, they tried to make the light as small as possible and that meant thinner walls so in that instance it would make complete sense to use 7075 since its twice as strong as 6061. However, lets just say they used 6061 instead. What are the chances of the battery tube crushing due to the thickness of the wall. 

How much more does 7075 cost in terms of material and manufacturing (is it as hard a hard material to work with like stainless steel). If the cost wasn't substantial than I'm all for having a harder alloy. It never hurts to have the light stronger.


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## Stress_Test (Jul 9, 2008)

*Re: 7075 vs. 6061 Aluminum*

Go to "matweb.com" and type in the alloy number in the search box (6061, etc.) 

It's a great site for browsing different materials of all kinds, and reading about their properties. 

Have fun!


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## mudman cj (Jul 9, 2008)

*Re: 7075 vs. 6061 Aluminum*

And here is a thread from last year with a discussion on this topic.


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## gadget_lover (Jul 10, 2008)

*Re: 7075 vs. 6061 Aluminum*

Thanks Mudman. I knew it had been discussed before. 

What it all comes down to is engineering. If you know the properties of the material you can design the light around those characteristics.

When you desire a specific design or dimension, you chose a material that can meet those specs.

And last but not least... When you have a budget, you choose materials that make manufacturing easier.

Daniel


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## DM51 (Jul 10, 2008)

*Re: 7075 vs. 6061 Aluminum*

I'm merging this thread with the one linked by mudman_cj.


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## half-watt (Jul 10, 2008)

here's one other point i'd like to make.

other than perhaps the threads (particularly fr/over torquing heads and tailcaps), i don't see a flashlight being exposed to repeated stress cycles and vibrations, like those experienced by an aircraft - particularly a helicopter. so, fatigue characteristics, other than for the head and tailcap threads, probably don't matter at all.

also, i don't know if thermal cycles really produce what an engineer would term "damaging cycles" leading to eventual crack formation, propagation, and ultimately failure. i rather doubt that they do. if they did, the number of cycles would probably be out at ten to the eighth or ninth cycles since the stress of each damaging cycle is so low, but still above the s/n curve for the light (though i think that these thermal cycles would be below the endurance limit of the alloy used). in other words, practically speaking, we would never have a fatigue failure fr/thermal cycling. or, from any other fatigue related cycling.

therefore, i'm not sure that the greater elasticity of 6061 alloys versus 7075 alloys is a benefit for a flashlight application. sure, 6061 can undergo more (i.e. a greater percentage) elastic deformation w/o yielding than 7075, but it does this when subjected to a lower stress than 7075. so, do i want an alloy that will give a bit more when subjected to smaller stresses, or do i want an alloy which has less capability for elastic deformation, but will only undergo yielding at a much higher stress? to my way of thinking, considering only this aspect, i'd opt for the 7075 alloy.

either way, fr/one perspective (viz. BEFORE crack initiation) Al alloys have good fatigue characteristics (i.e., they are more elastic, than let's say steel or Ti). however, fr/a different perspective, namely AFTER crack initiation, all Al alloys that i'm familiar with have very poor fatigue characteristics, since, cp. to steel or Ti, it takes relatively few cycles to produce significant crack propagation and failure.

therefore, fatigue issues are, IMO, not a concern - except for maybe threads if one repeatedly and significantly over torques the head and/or tailcap and even then, the number of total cycles are going to be relatively low (maybe at most, hundreds or a thousand or two over the service life of the light).

so, if fatigue is not an issue, what is? obviously, non-fatigue related issues such as static loading (e.g. stepping on or driving over the light w/a vehicle). considering only this basis, i'd go w/7075. however, in point of fact, what percentage of our lights get damaged in some way (e.g. a partially crushed battery tube)? so, it would seem that 6061 does suffice in most cases.


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## Mirage_Man (Jul 10, 2008)

One big advantage of 6061 is that it usually anodizes better.


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## Buck91 (Jul 10, 2008)

*Re: 7075 vs. 6061 Aluminum*

Ya know, there are a lot of high end bike stems and seatposts made from 2014-T6...


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## PEU (Jul 10, 2008)

PEU said:


> For annodized flashlights the best choices are 6xxx and 7xxx aluminium series, others don't annodize well according to the anno shop I use.
> 
> Then there is the price factor, 6061 or 6262 (the one I used for my last run) cost 1/2 of the same size 7075 and for a flashlight that wont be used as a hammer  IMHO there is no real need to go for the expensive alloy...
> 
> ...



I still think the same way a year after 


Pablo


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## Marduke (Jul 11, 2008)

I want an AAA light made out of 2195 :naughty:


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## VanIsleDSM (Jul 12, 2008)

Check out 7068-T6 Aluminum. It's the hardest aluminum I know of, never tried machining it though.

I searched that Kaiser sight for it:

http://www.matweb.com/search/DataSheet.aspx?MatGUID=72e595303f7d43fea0831c4ae268aa2d

It's quite a bit harder and stronger than both 6061 and 7075.. more expensive too obviously, but one of the biggest advantages is the thermal conductivity, it's also the highest of any heat treated aluminum.. 

I'll have to phone the local metal supermarket to see if they can order it in. I'd like to try making a light from some of that stuff.


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## VanIsleDSM (Jul 16, 2008)

So I checked locally, and I can't seem to get this 7068 aluminum. I'd really like to try making a light out of this stuff. Mcmaster carries it, but I already tried ordering from them, they won't ship to Canada. So.. I was thinking maybe someone would want to go halfers on a 6' bar 1.25" DIA. ? It's $150 for the whole bar to split, and costs $87 for 3'. So you get a good deal if you just want a bit to experiment like I do.

If someone is in PM me and work out the details, I'll obviously pay the extra shipping to Canada from you.. just cut the bar in half when you get it 

Here's some data on this aluminum comparing to other aluminum and titanium Ti-6Al-4V (Grade 5), annealed, which is the hardest I could find, what type do you use MirageMan?

Ti-6Al-4V (Grade 5), annealed:

Hardness, Brinell: 334
Tensile Strength, Ultimate: 138,000psi
Tensile Strength, Yield: 128,000psi
Shear Strength : 78,900psi




7068 T6, T6511

Hardness, Brinell: 190 
Tensile Strength, Ultimate: 103,000
Tensile Strength, Yield: 99,100
Shear Strength : 52,900 




7075-T651

Hardness, Brinell: 150
Tensile Strength, Ultimate: 83,000
Tensile Strength, Yield: 73,000
Shear Strength : 48,000




6061-T651

Hardness, Brinell: 95
Tensile Strength, Ultimate: 45,000
Tensile Strength, Yield: 40,000
Shear Strength : 30,000


All taken from MatWeb, same order as above:
http://www.matweb.com/search/DataSheet.aspx?MatGUID=a0655d261898456b958e5f825ae85390
http://www.matweb.com/search/DataSheet.aspx?MatGUID=72e595303f7d43fea0831c4ae268aa2d

http://www.matweb.com/search/DataSheet.aspx?MatGUID=4f19a42be94546b686bbf43f79c51b7d

http://www.matweb.com/search/DataSheet.aspx?MatGUID=1b8c06d0ca7c456694c7777d9e10be5b




This 7068 will also take an anodizing quite well.. with a shell almost as hard as diamond, and an intertior core twice as hard as regular 6061, I think it would be pretty durable. Without the soft aluminum under the ano to deform, the ano won't chip near as easily. Much more economical than Ti, and machinability is rated the same as 6061. I'd really like to give this stuff a go, could be great.


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## Tekno_Cowboy (Jul 16, 2008)

The new Nitecore lights are made of 7075-T6 :thumbsup:


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