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Aluminum/Stainless Steel Polishing Help

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  • Aluminum/Stainless Steel Polishing Help

    I am working on some items for a good friend of mine. They are cast aluminum valve covers. I currently own a 1HP polishing motor with two speeds low and high (1640 RPM and 3650 rpm).

    Any tips for getting the casting marks out of the valve covers. I tried sanding with 220-320-600-800-1000-2000 but its still somewhat in there. He wants these to a mirror finish and I am struggling.

    Also for the intricate details any tips or advice? I am generally not a small intricate kind of finisher.

    In addition, for my business i do a lot of small stainless steel bottle openers, hand polishing is a pain, would a vibratory tumbler be better. the issue I have is the holes in the pieces tend to want to rip it away, while I try to lead on a face and not an edge it is hard to do sometimes with all of the holes. Picture is below of the item I need to polish. Click image for larger version

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  • #2
    I have no experience with vibratory polishers. I have polished a lot of stainless. To do those small items on a production basis using wheels and buffs seems like a real pain. As you have no doubt discovered, stainless is both very resistant to sanding, yet at the same time is kind of gummy. I would guess a tumbler or a vibrator would be the way to go.

    As for your valve covers. With aluminum, I usually begin with 150 grit, then 220, 400, 600. After that, emery on a hard sewn cotton wheel (hard sewn is the operative word here) takes out the 600 scratches. The problem most polishers have is not sanding the previous grit scratches out before moving on. If there are any 150 scratches remaining after the 220, they will almost surely not be removed by the 400. You must get all of the previous grit scratches out before moving on. After the emery, I use a white finishing compound and then a mildly abrasive liquid polish with clean micro fiber rags. (Clean, as in wash the new rags yourself.) This takes out those almost invisible scratches you can only see in bright sunlight.

    As for the intricate details. Felt bobs or one or two inch wheels in a die grinder is what I use. My magic weapon is this:
    It's a Chicago Pneumatic polisher max 2500 rpm. With a soft pad I can get into most places.
    And I made this for a 1200 rpm polisher.
    It's been useful as well.
    Last edited by Rasper; 08-29-2016, 07:44 PM.