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Author: Subject: Making Aluminum (cuttings) for easier milling of Al powder
RogueRose
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[*] posted on 7-9-2018 at 14:37
Making Aluminum (cuttings) for easier milling of Al powder


Looking at a lot of videos where people make Al powder it seems that most people are using small pieces of Al foil - largely because it is easy to find and it is supposedly pretty pure. Well I've found that this is far from ideal for many reasons.

First is the purity. When I've dissolved the foil in HCl I ended up with a lot of black/grey sediment and the acid quickly turned yellow, when I added enough Al to use up the HCl, the solution looked extremely dirty, almost black. When it settled, there was a bottom thicker layer of black/grey and the top layer was a deep yellow - which I kind of suspected as AlCl3 is yellow, but a pure solution of AlCl3 is actually clear. IDK what the contamination is, I suspect a lot is carbon. I've used Al from soda/beer cans and I didn't get this dirty mix and I got even cleaner looking solution when using hard drive platters as well as the body of hard drives which I suspect is an alloy but it produced clear salt solution.

When using strips of foil they usually end up balling up into very tight spheres and these are extremely slow to break up for some reason. If you tear up the foil in multiple layers at once, the foil doesn't break apart but forms a larger ball of Al. Not a great way to make grinding material.

I bought a cheap table saw w/ 1/4hp motor and it had an old finish cut wood blade (high tooth count but all steel - not carbide). I had some Al I poured from melted cans and such into a 1" x 13" x 9" thick slab and passed it through the saw. It cut extremely fine shavings which were collected with a clean vacuum (an old household vacuum cleaner works great).

The cutting was a little slow b/c the motor is weak and the blade isn't real sharp. I used a carbide blade (about 1/2 the teeth count) and it cut about 8-10x faster and I has shavings/cuttings just as fine (feed the Al slowly through blade). It's possible to put a few blades next to each other and make a wider cut and it's even better if you put a stronger motor on it (pretty easy and they can be had cheap). I found a 1HP and 2HP that I'm going to try with 6-10 blades so it will cut about 3/4" wide per pass.

These cuttings are all very fine unless you use a very low tooth count saw (like a ripping blade). A finishing or framing blade is a good choice and you will get maybe 200-300 tiny slices per CC or ml, which means it is already pretty fine. Putting this into a mill makes the process MUCH faster, taking about 5-25% of the time to make powder as compared to Al foil.

I've tried putting in some charcoal dust (about .5% by weight) and about the same of magnesium stearate (which is a waxy substance) and it seems to coat everything very well and the product is a nice dark grey. I had no problem with ignition when allowing air into the container after 16 hours of milling but it is possible some air leaked in as it milled (slight cracks in the milling container).

You can use a few different saws to cut the Al and find different sources for the metal. A good source is finding a metal working shop and ask for the cuttings/scraps. Offer to pay above market price and I'll bet they would be happy to sell it - I've found many that were happy to give a few blocks away (about 4-5 lbs of 1" x 6" x 3" blocks of pure Al alloy blocks). If you want to make this, look for an old table saw (older the better, especially if it has pulleys/belts to connect the motor) and if it doesn't have a "dust shield" you can make one from thin plywood or thin plastic - this should have a port to connect the vacuum.

Even if you wanted to use a blender or coffee grinder to make powder, it is MUCH faster with these shavings and I'd suggest sharpening the blades on the blender/grinder - it makes a HUGE difference in how fine the powder can get not to mention speed. Overall, this is much less efficient than a ball mill.


This can also work with Mg or Mg/Al and Mg cuts MUCH faster than Al.
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CouchHatter
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[*] posted on 7-9-2018 at 17:10


I've done this with tin bars and a miter saw, although I wasn't able to recover much. Also the blade I had was too fine, it was like tin mist. Can't beat a lathe:(

Isn't it hard to make your own magnesium bits because of its reactivity? I have read about the conditions required to work with it, like having it fully submerged in coolant. I have only read, though, never done! Maybe the danger is exaggerated.
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RogueRose
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[*] posted on 7-9-2018 at 17:50


Quote: Originally posted by CouchHatter  
I've done this with tin bars and a miter saw, although I wasn't able to recover much. Also the blade I had was too fine, it was like tin mist. Can't beat a lathe:(

Isn't it hard to make your own magnesium bits because of its reactivity? I have read about the conditions required to work with it, like having it fully submerged in coolant. I have only read, though, never done! Maybe the danger is exaggerated.


I'd like to try this with zinc and tin as well.

A miter saw is not ideal for this because of the way the blade works and where/how chip collection is done. With a table saw, the blade is coming downward in front of the metal and the chips are brought down underneath the table surface. Enclosing the blade in a "sheath" that has a vacuum port directly underneath where the blade meets the metal allows for great flow as the metal is pushed right to the port and the air movement pulls the chips in.

As for Mg, i've only tried small blocks (fire starter blocks) and I didn't have problems, but my saw runs at about 1/2 speed of normal saws but it has a very high tooth count, so lots of very fine chips, smaller than from a lathe.

I've also tried drilling with a 1/2" bit in a drill press and that makes much larger chips, but they are still better than the foil balls.

I'm considering making a cyclone connector and having oil in the bottom so the chips/dust falls into the oil so they don't oxidize. IDK if that is the best option, I figure mineral oil would work well.

As far as using oil while cutting, I didn't with the Al but I'm suspecting that they do form a layer of oxide on the chips. Maybe catching in oil would help, but it would need a good cleaning before milling (not easy).

The Al I collected from the drill bit didn't seem to oxidize very much as the surface seemed to remain shiny, I guess the oxide might be able to be shiny though (foil is...).

I'd like to find some place that works with Mg and has scrap pieces to try this with but IDK what kind of shop would do a lot of work with Mg.
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[*] posted on 19-5-2019 at 18:43


I shredded some tin using a table saw with a cheap 1-gal tupperware. I recovered 80% of the tin I started with, so it worked far better than a miter saw! Thank you for your advice.

Without any way to gauge the mesh, though, I'm not sure how it will do for some of the reactions I have planned. I'll post back when I get around to using it.
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[*] posted on 20-5-2019 at 14:18


If you are going to use a saw like that it would be worth investing in a blade intended for cutting aluminium. The teeth are designed differently to a wood blade, which helps with chip formation and prevents binding - aluminium is quite 'sticky', especially if pure.



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[*] posted on 20-5-2019 at 17:02


When starting with scrap cans etc it may be easier to melt the cans,
(plastic coatings, shrink-wrap labeling, residues ... NO liquids obviously)
remove the dross, slowly and carefully pour into water to get fairly clean aluminium globules.
Cans aren't pure aluminium, always an aluminium alloy, of variable compsitions.
A wood or charcoal fire, with a fan, can easily melt down aluminium in a steel pot or even can (red to yellow hot works quickly).
I'd expect the fumes to be toxic so take care (stay upwind)




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vmelkon
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[*] posted on 4-6-2019 at 08:59


Quote: Originally posted by Sulaiman  

Cans aren't pure aluminium, always an aluminium alloy, of variable compsitions.


Source:
https://aluminum.org/resources/industry-standards/aluminum-a...

America’s favorite beverage container, the aluminium can, is made from multiple aluminium alloys. The shell of the can is composed of 3004 and the lid is made from 5182. Sometimes it takes more than one alloy to make one, everyday item.

3xxx Series
Manganese is the major alloying element in this series, often with smaller amounts of magnesium added. However, only a limited percentage of manganese can be effectively added to aluminium. 3003 is a popular alloy for general purpose because it has moderate strength and good workability and may be used in applications such as heat exchangers and cooking utensils. Alloy 3004 and its modifications are used in the bodies of aluminium beverage cans.

5xxx Series
Magnesium is the primary alloying agent in the 5xxx series and is one of the most effective and widely used alloying elements for aluminium. Alloys in this series possess moderate to high strength characteristics, as well as good weldablility and resistance to corrosion in the marine environment. Because of this, aluminium-magnesium alloys are widely used in building and construction, storage tanks, pressure vessels and marine applications. Examples of common alloy applications include: 5052 in electronics, 5083 in marine applications, anodized 5005 sheet for architectural applications and 5182 makes the aluminium beverage can lid. The U.S. military’s Bradley Fighting Vehicle is made with 5083 and the 7xxx series aluminium.


If you want high purity, you have to get electrical wires. These are made of Al series 1xxx.
Example: Aluminium 1199 (99.99% min. purity)




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