How do i polish aluminum?

[touser]

Hello everyone, i have been searching the forum and google for information on how to polish aluminum and thus far all i have found is ways to polish it to a mirror finish. The information i am looking for is how do i make it look like this: http://www.ultimatepedals.com/catalo...ooth_satin.jpg

I just machined a custom dead pedal for my car out of boredom and it is covered in machining marks and is entirely too shiny and just doesn't match the stock pedals at all. Here are some pictures for a comparison:
http://crystalcove.ath.cx/pics/cad/d...deadpedal1.jpg
http://crystalcove.ath.cx/pics/cad/d...l/carafter.jpg

Thanks for any help in advance!

[harvard5]

It looks like the finish you want is a bead blasted finish. Where the part is sand blasted with glass beads (almost a powder in size of bead) We do this all the time on aircraft parts.

Bill

[touser]

Thanks for the reply harvard. Considering i dont have access to sandplasting equipment i suppose i could comprimise with a finish like this: http://www.ultimatepedals.com/catalo...th_brushed.jpg
does anyone know how to achieve that look? Thanks again!

*edit*
actually, after looking at how cheap sandblasters can get how would i go about sandblasting it to achieve that look? I am also curious as to how to achieve the brushed look as well though. Here is a sandblaster for $50, would it do the trick? http://www.amazon.com/gp/product/B00...52024?n=228013

[James Marshall]

Hello, I am new here but I may have some ideas for you. Using glass beads will give you the finish you want. You can but it at Grainger if you have access to an account, though it comes in a 50 lb bucket, or at Eastwood. Its finest grit size is like powder but you can purchase it in a couple of coarser grits. Never use more than 40 psi with glass or you will waste it. The higher pressures will turn it to a baking powder like substance. Glass bead is not verry agressive, but will remove light rust and paint, and is used for prep prior to painting and powder coating. If you are going to use a blaster like the one fron Northern than you can recover it off the floor but will have to buy a seive to filter it. Better yet you can buy a benchtop unit from someone like Eastwood or Northern. This way you wont have to recover it and it wont make a huge mess in your shop. Be aware of needing to protect yourself from the dust with PPE. Eastwood is a good sourse for other finishing and metal working supplies. I hope this helps.

[mdreitzusa]

if your going to try the blasted finish.you could try one of these sand blasters.they would be ok for hobby use.
http://www.harborfreight.com/cpi/cta...emnumber=92857
http://www.harborfreight.com/cpi/cta...emnumber=30979
the other finish look like the finish i use.it is easy to do just sand the surfice with long strokes in only one dirrection.the git you use will determin the final finish.
another idea would be to use an anodized type finish.something like this.
http://www.duplicolor.com/products/metalcast.html
you can get it at napa or walmart.

[greybeard]

Being an ex-lab tech rather than an engineer, the first idea I would try is etching with an alkali.
I'd take a piece of the same stock with the finish as per your pedal, de-grease it thoroughly( no fingerprints!) then sart with hot washing soda solution in a pyrex dish, as the safest starting point.
If that didn't give you a deep enough etch, I'd next try cold caustic soda solution. Both attack aluminium giving of hydrogen in the process.
Best not to smoke
In both cases you need to take appropriate care, and carefully wash off all traces - lots of water, then dry (low oven) before handling.
You'll notice they are both household products, and very cheap.
More info if required.
John

[touser]

Thank you all for the help i really appreciate it. I think i will run to harbor freight later and pickup a small sandblaster and give it a shot on a sample piece of metal later today. Also, the etching idea really intrigues me. I will have to find out where to buy the necessary chemicals and give it a shot as well! Thanks again everyone for all of the help i would be lost without you! Also one last question; while sandblasting with glass bead with one of those smaller sandblasters from harbor freight what kinda of safety equipment will i need and will there be any way to recover the glass bead? Can i put my work inside a bucket to try and minimise the mess?

[seidlry]

Personally I would just wet sand it with 320 grit wet sand paper in the direction you want the brush finish to be in . The aluminum I have glass bead blasted in the past seems to get stained easily and the only way to clean it is to bead blast it . The best finish would be to anodize it after you bead blast it . here is a link to a home anodizing kit and tips .
http://www.focuser.com/atm/anodize/anodize.html

[greybeard]

Washing soda and caustic soda are old fashioned methods of degreasing. W/soda generally replaced by detergents, caustic for drain cleaning.
They also work as preliminary preparations of aluminium before anodising.

[motomitch1]

RED DEVIL "Lye" drain cleaner mixed with 3 gal. of water will give it a matte finish it only cost a few bucks. That will work on 6061 but if it is 2024 alloy or 7075 that has 5% copper in it will turn black then you have to desmut it. Desmut is a mixture of sulfuric and ferric acid.

These are all common acids that are used for DIY anodizing aluminum at home.

[touser]

Thanks for the reply's. I went to harbor freight today and they had a whole sandblasting enclosure with gun on sale for $80 so i picked it up and am going to give it a shot on some scrap aluminum i have. motomitch1, for the 3 gallon mixture do i just set the piece of aluminum in the bucket for a certain amount of time and then its done or does it just need 3 gallons to be diluted enough so i can then rub it on?

[motomitch1]

Thats diluted for 1 RED DEVIL "Lye" drain cleaner you could do a 1/2 of a can to 1.5 gallon of water
you wont have to rub it on, just set it in there for 5 or 10 min. and rinse it off with water.

sandblasting with some really fine sand might be closer to what you looking for looking at your pic.