Finishing Aluminium

[williamwright]

then acetone, then primer, then spray.

Bill

[thescullster]

Hi Guys

I am profiling a bracket shape out of 12 thk aluminium.

Got as far as the rough profile with a jig saw and a bit of chain drilling and will dress it to shape with a file next. The question is, how do I get a decent finish on this? The edges will need tidying as will some scratches that were already present in the metal surface.

Is this a job for ever increasing grit sand paper? How do I achieve a polished finish if that isn't asking the obvious?

Thanks

Phil

[The Natural Philosopher]

yes

Wver increasing grit sand* paper? Followed by a buffing wheel and cutting/polishing compound

*wet and dry, used wet.

It won't stay shiny long though. Not aluminium. Always ends up looking dull and slightly oxidated.

[Martin Brown]

It will be fine if you lacquer it or it is in a nice dry environment. Humidity and alkalis are the enemy of aluminium metal.

Its weak point will be the screws/bolts since dissimilar metals in contact also leads to corrosion problems.

Anodising will work but not for a mirror finish. Not really DIY either.

[Thomas Prufer]

Yes.

I like something around 120 grit to finish, maybe 220. Sandpaper on table, push over it along a guide to get the final scratches parallel and straight to finish.

Finer paper, and/or Scotchbrite, and then polishing wheels: felt and sewn, with the buffing compounds. I have cheap Wolfcraft "Hobby Polishing Set", felt and sewn wheels, blocks of compound, an arbor, goes in a drill. Works fine, will take ally to mirror finish with patience. (Leaves a black waxy mess imbedded in your finger skin:-)

Thomas Prufer

[Brian Gaff (Sofa]

Normally you would not aim for shiny, more a brush look,with a mildly abrasive rotating brush of some kind. Then of course, if you are really keen, you may need to get it anodized professionally, or maybe dipped in alochrome to seal it. The latter gives a kind of almost satin finish with tinges of gold sometimes in certain lights. Not as hard as anodising though. Brian

[nothanks]

Finish the edges by draw filing (file used at 90 degrees to normal use) with a fine file

[The Natural Philosopher]

self taps for thin sheet, but tap holes for machine screws in thicker Or use some kind of nut insert - Al is not strong in shear...

[thescullster]

Thanks for all the advice guys.

Had forgotten the term draw filing as I have been away from the tools for decades. Will have to look at the most appropriate fasteners as I will be tapping screws into the aluminium body.

Phil

[Dave Plowman (News]

At school, we were taught not to use the best files on ally, as it clogs the teeth. But that was before the days of readily available abrasive sheets of all types.

[nothanks]

Chalk or paraffin can help with clogging, and my remaining memory pixies seem to think that caustic soda solution can be used to clean files that are clogged with aluminium