So if using the metal shop grinders is forbidden while working with Aluminium, what does one use to grind welds, remove burrs, etc ?
Flap wheel disks on the angle grinder will load up and become worse than useless quickly on aluminum, but they generally won’t fail like grinding wheels. There are also expensive angle grinder wheels rated for aluminum, but the space doesn’t stock them, and you may be stopped occasionally to prove what you are using if you bring your own.
2 Likes
Belt sander, disc sander. They will still load up if aggressively used but they wont Explode!
3 Likes
They aren’t too bad on price…
Fastenal is a quite a bit more than Amazon…
4 Likes
Just in case it’s not clear to you or anyone else that stumbles across this thread in the future:
The reason that it’s forbidden to grind aluminum is that the metal itself is too soft, and literally fills in all the tiny spots between the grains of the wheel. This is bad for two main reasons.
-
It can cause catastrophic failure of the wheel itself. The wheel can literally crack and split apart, usually under load when a user is very close to the wheel. There is a tremendous amount of energy stored in the wheel and there is a high chance of injury or even death due to the forces involved.
-
It fouls the wheel. Filling in the wheel means that it’s not going to grind anymore, and has to be replaced.
11 Likes
Definitely grinding wheels on aluminum is a recipe for disaster. Working aluminum usually requires specialty tools that are different than the common variety for steel. In general, anything you use for aluminum should ONLY be used for aluminum. I mark all my aluminum stuff specifically so I don’t cross contaminate my work.
Using wire brushes, sand paper, flap wheels, etc. on ferrous materials, or others and then using them on aluminum will deposit that other material in the aluminum and make it harder to weld or to get a good finish.
An exception to the rule would be files. A file can be cleaned between uses, so as not to deposit material into the surface of the aluminum. It is a bit more work doing it that way, but it saves the cost of buying a double set of files.
After welding, cleaning, and so on, a scotch brite pad makes a nice ‘brushed’ finish on the surface and can make your finished piece look like it was one continuous piece of aluminum. There are different ‘grits’ of scotch brite that can be used.
I also tend to use water or sometimes WD40, Boe-lube or other lubricant when doing finish work on a completed piece. This prevents the paper from loading up. The scotch brite pads have a built in lubricant.
Prior to doing any finish prep for paint, powder coat, etc. It is a good idea to wipe the whole piece down with soap and water, and then finally a good wipe down with acetone and a clean cloth. If possible, baking it for a while to off gas any other contaminants is a good idea too. It all depends on the finish you want and what you have available to you.
2 Likes
For deburring things like thru holes or edges, you can used a deburring tool. It looks like a thick razor blade and literally shaves off the burr as you drag it across the edge of the material. There are also tools that look like a big counter sink on a screw driver handle. Both varieties can be sourced at Harbor Freight for a few dollars for what I would consider to be low to mid grade… and Aircraft Spruce for more professional grade at a commensurate cost.
If deburring a hole, you could also use a drill bit a few sizes larger and turn the edge by hand. Before I had the more ‘specialty’ tools, that was how I cleaned up all my dzus fittings and rivet holes.
This video explains some of the different ways to deburr… he starts explaining the tools about 1:40 into the video.
Hope this helps 
1 Like
Scotchbrite wheels work well, but I don’t like them on a grinder. I chuck them in a drill press instead. They’re expensive. 1x6 wheel is $100.
Also scotchbrite roloc pads in an air angle die grinder work great and are cheap.
I’ve never had to grind an aluminum weld… No idea about that. Scotchbrite is like fine sandpaper for aluminum… smooths things out.
Yeah, I use mainly the roloc/drill variety, or just the sheets. I veered off the machine topic a bit there and got more into the finishing / prep for paint side of it.