# Turning Aluminium bar vs tube?



## piesoup (Sep 24, 2009)

Hello
I have been turning ali bar for quite some time and have noticed about 80% of the metal ends up in the swarf tray.
What is ali tube like to machine? I would have hardly any waste as I can buy near enough the correct diameter. As it is most probably extruded, I'm expecting a less than perfect finish.
I use a 8x14 lathe with tungstun cardboard tips.
Any advise??

Thanks


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## saabluster (Sep 24, 2009)

piesoup said:


> I use a 8x14 lathe with tungstun cardboard tips.
> Any advise??



Try changing your tips to tungsten carbide.
 


Sorry I don't have any real advice to give but I just couldn't help myself.


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## Doh!Nut (Sep 24, 2009)

Tube is fine, its not round but then again the bar is not either.
I try to skim off some od (until I am down to new metal all the way round) and square up the end before turning the piece end to end to finish the od and tidy up the id. That seems to give me a pretty good start point that can be removed from and returned to the lathe with a reasonable chance of being concentric again.

The only other thing is you will notice the more flexible tube will be more prone to chatter.

Nick


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## precisionworks (Sep 24, 2009)

Most commercial manufacturers of hollow aluminum products start with tube that's near net size. As Doh!Nut said, the OD needs to be slightly over size to allow a cleanup cut, and the ID has to be slightly under size for the same reason. For machining any material, whether aluminum, Ti, brass or unobtanium, the closer you can start to finished size, the faster you can complete the part.

A customer ordered 500 bronze bushings, about 2" long, 1.50" OD and 1.25" ID, which was done at a local CNC shop. The material cost was roughly half using tube, and the machining cost was also much less. If you have the material shipped to you, you'll also pay less in shipping charges.


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## KC2IXE (Sep 24, 2009)

Tube generally machines fine - depends on the alloy

As for roundness - there are generally 2 kinds of "tube" Extruded and Drawn over Mandrel (DOM). DOM usually is a lot more accurate as to size/shape


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## tino_ale (Sep 24, 2009)

Is it easy to source 6/4 Titanium in tubes?
Is the material different from solid bars? I mean extruded versus "I don't even know how bars are made" ?


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## piesoup (Sep 25, 2009)

Thanks for the replies chaps
I think I will go for the tube now that you have reassured me it'll be ok! It'll save a hell of a lot of boring boring!
precisionworks, I forgot about the obvious savings in postage too! 

Thanks


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## gadget_lover (Sep 25, 2009)

While you save a heck of a lot of boring by buying tube, it's not a bad idea to stock both.

Use the tube when appropriate, and use the solid stock when you do not have the right size tube available. Sometimes when you want a light to be scuplted you become constrained by tubing sizes.

Daniel


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## precisionworks (Sep 25, 2009)

> Is it easy to source 6/4 Titanium in tubes?


In the USA, a good source for decent priced tube material is Titanium Joe ... but he mostly carries tube in Ti 3-2.5. This grade is often seen in bicycle frames, golf clubs, and aircraft tubing. It's not as strong as Ti 6-4 (90 ksi vs. 130 ksi). Most, if not all the tubing currently on eBay is Ti 3-2.5.

http://stores.shop.ebay.com/TITANIU...804QQ_sidZ27772198QQ_trksidZp4634Q2ec0Q2em322

Ti 6-4 is more readily available in solid rounds, although the tube form is not uncommon. If you want to keep the price down, but still want the light weight, corrosion resistance & strength of Ti, you may want to try 3-2.5.


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## piesoup (Sep 26, 2009)

gadget_lover said:


> While you save a heck of a lot of boring by buying tube, it's not a bad idea to stock both.
> 
> Daniel



Definitly! The round bar will be used for press fit heatsinks and such like.


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## will (Sep 27, 2009)

One thing with aluminum tubing. It is made by pushing the molten metal through a die (extrusion) The metal welds itself back togetheras it is passed through the die. If you look at the tubing, you can see this weld line, you have to look really close, I mean really close. If you have the aluminum part anodized, you might be able to see this line, This will show up even if you turn down the OD and the ID. Here again , you have to look really close. To be fair here - I am really nitpicking .....

My understanding of this is due to the fact the weld line has a slightly different heat treatment at that point resulting in a slightly different alloy. 

I had a few Mini-mags HAIII treated, I could see the lines from the extrusion. 

Solid bar does not have this issue.


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## tino_ale (Sep 27, 2009)

will said:


> Solid bar does not have this issue.



How solid bars are made? and does a Titanium tube have the same "problem" than an extruded aluminium tube?


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## gadget_lover (Sep 27, 2009)

I think that small bars are drawn through dies to get them to the right size. IIRC, large bars are rolled to dimesnsion.

I could be wrong.

Daniel


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## will (Sep 27, 2009)

gadget_lover said:


> I think that small bars are drawn through dies to get them to the right size. IIRC, large bars are rolled to dimesnsion.
> 
> I could be wrong.
> 
> Daniel



I think you are correct


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## tino_ale (Sep 28, 2009)

So, just to make it clear, there is a difference in the alloy you are getting when using a tube of aluminium versus a plain bar.

My question is : is it the same with titanium? Are you getting the exact same alloy from a tube vs. a bar, say, once you're done with your machining work and the part is finished?


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## 65535 (Sep 28, 2009)

One thing about using tube stock is that you have to machine threads into the ends to accept a plug. With solid round stock you can just leave a section of the body intact as the end.


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## precisionworks (Sep 28, 2009)

> is a difference in the alloy you are getting when using a tube of aluminium versus a plain bar.


There certainly could be. Whenever metal is purchased, the seller will list the metal identification number - like 6061-T6, Ti 6-4, etc.

Different alloys of any metal have different mechanical characteristics. In aluminum, two different alloys will not anodize to the same color.



> is it the same with titanium? Are you getting the exact same alloy from a tube vs. a bar


If you buy Ti 6-4 tube and Ti 6-4 bar stock, the alloy composition is identical (within manufacturing tolerance limits). The only way to get exactly the same alloy is to buy all the material from one heat or lot number.


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## will (Sep 28, 2009)

I had a few Mini-Mags re-anodized HAIII, I even had 2 of them ceramic coated white. The bodies came out a slightly different color than the head, bezel, and tailcap. I am reasonably sure the body is made from tube stock, the other parts from solid bar. Maglite would not release the alloys used, but, I have heard that they are all 6061. I am not a metal expert, so I can't give what the tolerance might be in 6061 aluminum. 



I can't speak to titanium, no experience with that metal in a long, long time.


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## wquiles (Sep 28, 2009)

will said:


> The bodies came out a slightly different color than the head, bezel, and tailcap.



+1 

Every time I have had HAIII done, or have seen pictures of HAIII done on Mag's, the head, bezel, body, tailcap all look "slightly" different, sometimes more significantly. 

For example, all except from the one on the very left are all supposed to be HAIII. From left to right:
FL12, FM HAIII 2C, MM 2C HAIII, FM 1.5D, Modamag 1D, MM HAIII 1C:


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