How to "Clean Up" Satin Finish Aluminum???

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toddalin
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How to "Clean Up" Satin Finish Aluminum???

Post by toddalin » Wed Apr 03, 2019 2:38 pm

I had a machinist make a bunch of aluminum spacers, and he did less than a stellar job on the finish. The fact that he dropped the box (45 pieces), certainly didn't help. It is a brushed satin aluminun, and I believe the finish is obtained using a "scotch brite" tool. This shows one on my website:
Image

I've tried to use a green scotchbrite pad and just rubbing the piece seems to make more scratches than it removes. So what would be the best (i.e., easy and cheap) to clean these up? I do have a small mill.

Thanks.

Harold_V
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Re: How to "Clean Up" Satin Finish Aluminum???

Post by Harold_V » Wed Apr 03, 2019 3:45 pm

Glass bead blasting will blend all scratches to a uniform finish. By varying air pressure and bead size, you can achieve a texture that pleases you.

While it's not a perfect solution, you can protect the finish by having the parts anodized. That offers the opportunity to dye the parts to a chosen color, or they can simply be clear anodized. The resulting surface isn't very deep (just a tenth or two), but it's hard enough to prevent superficial scratching. The finish can be made matt (if that's your desire) by etching the parts before anodizing.

It's possible the parts were originally tumbled (or finished in a vibratory) with a specific media. That, too, will provide a uniform finish--without grain.

H
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toddalin
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Re: How to "Clean Up" Satin Finish Aluminum???

Post by toddalin » Wed Apr 03, 2019 5:58 pm

I do have access to both course and smooth media cabinets, and this is certainly worth a try. Thanks.

They were not tumbled and everything you see was done on the big CNC mills; first a Fidal, then two different HAAS. I had been to the shops several times.

Harold_V
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Re: How to "Clean Up" Satin Finish Aluminum???

Post by Harold_V » Thu Apr 04, 2019 1:39 am

It's hard to discern the finish from the pictures, so I'm not sure I understand the brushed satin one you mentioned. I suppose a rotary brush could have been applied, which, with CNC's, would be easy enough. I'd enjoy hearing how the parts had the desired finish applied.

Aluminum is just too soft to expect any type of finish to be resilient enough to withstand any contact. Even grit on your fingers will alter the appearance, so if finish is important to you, consider anodizing, as I mentioned. That process creates a thin film of aluminum oxide, which is exceedingly hard. They also seal the surface after the process, so it isn't subject to staining. The sealing process closes the pores that are created in the anodizing process.

Without seeing the problems you mentioned, I'd consider them quite nicely made. They sure look good at my end, anyway.

H
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shorttrackhack
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Re: How to "Clean Up" Satin Finish Aluminum???

Post by shorttrackhack » Thu Apr 04, 2019 10:15 am

I use a 3 1/2" wide Dyna Cushion wheel mounted on and electric motor, or sander/polisher. Scotchbrite bands are available in brown, red, blue, and gray, as well as cloth/resin backed abrasives. For long and large panels, I use an air file (like for bodywork) with Scotchbrite pads spray glued to old sanding strips.

shorttrackhack
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Re: How to "Clean Up" Satin Finish Aluminum???

Post by shorttrackhack » Thu Apr 04, 2019 10:20 am

Seal the surface with car wax, it will keep it shiny for a while and keep the aluminum off your hands.

toddalin
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Re: How to "Clean Up" Satin Finish Aluminum???

Post by toddalin » Thu Apr 04, 2019 2:47 pm

I tried the blast cabinet. The fine media cabinet wasn't working and I tried the course media. Interesting finish, but rough. Certainly gets rid of the scratches. Will try this one again with fine media.

http://headerbracket.com/index.html

Very unhappy with this "machinist." All others separated the pieces when finished and he just threw them in a box together to bang on each other, then dropped the box.

Harold_V
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Re: How to "Clean Up" Satin Finish Aluminum???

Post by Harold_V » Thu Apr 04, 2019 3:50 pm

toddalin wrote:
Thu Apr 04, 2019 2:47 pm
Very unhappy with this "machinist." All others separated the pieces when finished and he just threw them in a box together to bang on each other, then dropped the box.
For that I don't blame you. Regardless of finish requirements, a good machinist won't package parts that way.

Playing with the air pressure when using glass beads can spell a difference. If fine beads aren't doing much, increase the air pressure. Keep in mind, so long as they are not degrading (turning to dust), they don't cut, they just peen. However, once they start turning white, they have been fractured, resulting in smaller, but sharper particles, so they tend to cut better, but with a different patina. The faster they get propelled, the better the chance they'll begin fracturing.

H
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RSG
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Re: How to "Clean Up" Satin Finish Aluminum???

Post by RSG » Fri Apr 05, 2019 7:33 am

If I may add to Harolds advice, you can also use Sodium Bicarbonate (baking soda) in your blast cabinet which produces a nice soft satin finish but as Harold mentions this is just cosmetic and does nothing to protect the part. Judging by your website these items must have some level of cosmetic value so it would just go without question for me to say they must be anodized. Once installed it's a matter of time before they start to oxidize and marr. If you do decide to anodise be very careful what type of blast media you use as anything with silicates will give a failure on the ano outcome.
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toddalin
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Re: How to "Clean Up" Satin Finish Aluminum???

Post by toddalin » Fri Apr 05, 2019 1:17 pm

Anodizing is out of the question due to expense. My profit on each of those aluminum pieces is only about $8 with my labor, and anodizing would kill that.

I've had some of these sitting in a box for over 4 years and they still look like new. Once mounted, it is up to the user to keep them clean. Or, they can purchase them in a polshed finish, and these also still look new.

This is my Chinese competition:
Image

And this is my all American product:
Image

toddalin
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Re: How to "Clean Up" Satin Finish Aluminum???

Post by toddalin » Sat Apr 06, 2019 4:57 pm

I was going to try the finer media for blasting, but the cabinet wasn't working. When I noted this to the staff, it didn't matter because they had now loaded both cabinets with coarse media. Figures! Of course I can bring in my own media.

But..., I was remined that there is also a small vibratory tumbler, so I'll give that a try next time. It looks to be loaded with small wet stones.

Harold_V
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Re: How to "Clean Up" Satin Finish Aluminum???

Post by Harold_V » Sun Apr 07, 2019 1:53 am

One of the advantages of a vibratory is that the resulting finish, if the media choice is correct and the time in the machine is long enough, is that surfaces that you may desire to have a high luster can quickly be brought about. They leave a very nice surface, albeit frosty.

What mounts on those spacers? I was surprised to see they're for an engine.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

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