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Polishing cast aluminum

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  • Polishing cast aluminum

    I am about to polish aluminum for the first time. I purchased the necesary wheels and buffing/polishing bar (sisal, sprial sewn, loose sewn wheels, black, brown, and white rough bars) to polish my aluminum valve covers. The valve covers are casted aluminum. Do I have to sand them down with wet sand paper before I use my wheel with the black emery compound? What grit should I start and end with on the sanding? Thanks.

  • #2
    YOu definetely must sand!...Depending on how rough the casting is, you might get away with starting at 220 wet...to get those pits out though you might need something as low as 80 grit!.Start out high and work lower if need be...don't make any MORE work for yourself!..Good luck with it, and post some photos of the finished product!!! Dave S.
    WWW.DSMETALPROJECTS.COM

    Polishing and Motocycle customization

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    • #3
      Start with 120 - if it's too slow for you drop to 80, then 120/220/320/ No need to go wet til at least 220. For the best job finish off with 500-600 wet, then emery/spiral.

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      • #4
        should I sand by hand or use a palm sander? The valve cover has some curves so what is best? Thanks.

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        • #5
          glad you asked as i just finished a set last week. i use a small palm sander on the flats all the way thru 400 wet( i wet the part with a mist bottle. if you try this and shock yourself you are on your own) as for the curved surfaces i do this by hand. as for the wheels you have i would shy away from the sisal it might be too aggressive for the soft cast alum. after you spend all the time to sand to 600, sisal is going backwards. try emory and spiral. best of luck bro. keep us posted on how it works for you.
          when in doubt polish it out/ why replace it when you can refinish it
          G2 Polishing and Powdercoating

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          • #6
            thanks for all the responses. I am going to try to polish this weekend.

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            • #7
              I use an air jitterbug when necessary - no danger of shock there.

              But on those valve covers I usually use a drum sander, but gotta keep the piece moving to avoid ripples.

              BTW, don't be surprised if you find "pits", which are really pores within the cast aluminum - you'll never get these out since new ones will appear as you keep sanding. Nothing you can do about it unless you plate them.

              And, for you and all the newbies - I sure hope you are wearing at least a dust mask, preferably a respirator, while sanding and polishing. Ingestion of aluminum has been linked to nasty stuff, including the onset of alzheimer's.

              We should stress safety more in here.

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              • #8
                Originally posted by mpierich
                We should stress safety more in here.
                i fully agree it is not discussed enough. i have had a few incident's of parts being jerked out of my hands and such also had an allergic reaction to something a couple weeks ago and had to go to emergency due to lips and tongue swelling. all of the stuff we use can be dangerous if not handled responsibly. might be a good idea to make a sticky on this board with lessons learned and safety issues. any moderators agree.
                best of luck and stay safe.
                when in doubt polish it out/ why replace it when you can refinish it
                G2 Polishing and Powdercoating

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                • #9
                  << i have had a few incident's of parts being jerked out of my hands>>

                  Oh, yeah...when you figger the speed of the face of the wheel...I put my main machine next to a window, haha...gotta fix that someday, had a primary case hit it at 80 mph, good thing it's safety glass. But that hasn't happened in a long time (knock wood), seems the more I work the better I get at keeping the piece from doing that.

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                  • #10
                    I have shot a valve cover right in to the yard .. my machine is in front of the door and a loose grabbed it and off it went.. i got to put ply wood up on the wall in that area .. the dry wall has some battle marks

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                    • #11
                      Originally posted by customandsound
                      I have shot a valve cover right in to the yard .. my machine is in front of the door and a loose grabbed it and off it went.. i got to put ply wood up on the wall in that area .. the dry wall has some battle marks
                      Ha, I was thinking of hanging an old mattress...all polishers should be in a padded room anyhow...

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                      • #12
                        the first time i shoot one i was amazed that it went as far.. they the last time i shoot one i had a shop full of customers. but in the new shop i am putting padding up on the wall i got that soft mat mat + it will cut down on the nosie alittle... either that or i am going to have the kid there with a catchers mit on just waiting ...

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                        • #13
                          A shooting part is bad enough, but having to pick it up and see all the dings on a part that was almost done kills me.

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                          • #14
                            well, I tried to polish the valve colves last weekend and it did not turn out well at all. I sanded the covers with a 220,400 grit using the 1/4 sheet hand sander. then I manually wetsanded using 600 grit. After that I used the spiral sewn with black emery, spiral with brown, the lose with white. the result is depressing since it is now where near mirror finish. Infact, it looks like unpolished billet material instead how long do I have to spend on each wheel? how much pressure? I was using a 1/2 hp converted sander and I can only get in about 5-6 minutes before the motor heats up and lose power. If I need to get a new motor, any recommendations for a decent motor but not too much $$$. Thanks.

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                            • #15
                              you need a new motor. i spend about 10-20 minutes on each wheel but i am running a 1.5hp at about 9000 sfm on the first wheel also you might need to use more pressure. there is no exacts in this game it is trial and error. if buffing didnt scratch or open pits/pores then you can rebuff until its as good as you want. i suggest the biggest buffing motor you can get/afford. if you are going to keep doing this kind of work it is a good investment to buy big and strong. quality is expensive but worth it. hope this helps bro.
                              when in doubt polish it out/ why replace it when you can refinish it
                              G2 Polishing and Powdercoating

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