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How-to: polishing aluminum (engine parts etc.) - step-by-step guide

Discussion in 'Exterior and Detailing' started by Nachtmensch, May 16, 2007.

  1. Nachtmensch

    Nachtmensch New Member

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    pulled this from mr2oc.com. thought you guys could use it :)

    -kevin



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    I get a lot of questions concerning my polished engine pieces. I think it's time to reveal the big secret (which is that there isn't one)! I took pictures of all steps needed to get from a standard >10 year old part to a shiny mirror-like show piece. I also wrote down the amount of time needed to complete each step. Now let's have a look!

    We start with the standard piece, in this case it's the coolant neck of a Gen3 3S-GTE engine.

    awww.carpron.com_multisite_d_127616_2_IMG_2464.JPG

    The first step is the most time consuming and important phase. The amount of work and detail you're prepared to bring into this phase determines how well it'll look in the end.

    To get the part to a smooth, mirror-shine finish we need to smoothen the surface of the part. Since this aluminum part is cast, the cast structure needs to be leveled. Aluminum is very soft and this can be achieved by hand-sanding the structure down with grit 80 sanding paper:

    awww.carpron.com_multisite_d_127621_2_IMG_2465.JPG

    I'm using a cork sanding block, which isn't too large and gives in a little. A hard, plastic sanding block wouldn't work as well because it's not flexible, making it much harder to sand curved surfaces.

    After the first stroke, this problem area becomes visible:

    awww.carpron.com_multisite_d_127624_2_IMG_2471.JPG

    The top is not completely round but has a weird shape. You could leave it like this, but as I said, this stage determines how well the finished piece will look. So I want this removed to create a nice round shape instead of what it is now. I use a big metal file to level the high areas. This is the result:

    awww.carpron.com_multisite_d_127627_2_IMG_2475.JPG

    I also filed down the casting seams at the top:

    awww.carpron.com_multisite_d_127630_2_IMG_2476.JPG

    The rest of the shapes were okay, these just required sanding. Do as much as you can with the sanding block, because you can easily apply pressure on it, making the work much easier. Also, when not using a tool like a block, you're bound to create waves in the soft material, which will show once it's completed. Compare it to body filler: you need the sanding block to create a tight, planar surface. If you'd sand the filler by hand, you'd create a warped surface.

    After sanding more:

    awww.carpron.com_multisite_d_127636_2_IMG_2480.JPG

    Here I filed away the ongoing casting seam with the same file:

    awww.carpron.com_multisite_d_127642_2_IMG_2485.JPG

    The file leaves pretty heavy scratches. 80 Grit sandpaper deals with it though:

    awww.carpron.com_multisite_d_127645_2_IMG_2487.JPG

    A bit further down, there's a small '2' cast into the piece.

    awww.carpron.com_multisite_d_127654_2_IMG_2502.JPG

    I used a miniature file to get rid of it:

    awww.carpron.com_multisite_d_127657_2_IMG_2508.JPG

    I used the large metal file again to level this:

    awww.carpron.com_multisite_d_127660_2_IMG_2510.JPG

    You can see how much material was removed by looking at the blank material. After more sanding, sanding and sanding, stage1 was completed.

    awww.carpron.com_multisite_d_127669_2_IMG_2515.JPG

    TIME NEEDED TO COMPLETE 80GRIT SANDING: 6-7 HOURS

    -------------------------------------------------------------





    The next stages are considerably shorter, and easier. 120 Grit sandpaper is up!

    awww.carpron.com_multisite_d_128663_1_IMG_2543.JPG

    In this picture, the top part has been sanded down with 120 grit, the rest is still 80. The idea is, that every scratch you made with the 80 grit sanding paper must be removed by the 120 grit. If you don't, you'll see it throughout the remaining stages!

    awww.carpron.com_multisite_d_128667_1_IMG_2552.JPG

    Here, the piece is complete done.

    awww.carpron.com_multisite_d_128670_1_IMG_2553.JPG

    TIME NEEDED TO COMPLETE 120GRIT SANDING: 1.5 HOURS.

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    The next stage is 220 grit sanding. Again, you should sand away all the sanding marks left by the 120 grit stage. All done:

    awww.carpron.com_multisite_d_128676_1_IMG_2560.JPG

    TIME NEEDED TO COMPLETE 220GRIT SANDING: 1 HOUR.

    -------------------------------------------------------------






    The next phase it 400. This is where it gets tricky, because this is one of the highest grits you can still dry-sand. Wipe off the paper often, because it tends to fill up with aluminum dust very quickly.

    awww.carpron.com_multisite_d_128680_1_IMG_2562.JPG

    As you can see, the piece gets shinier by the hour!

    TIME NEEDED TO COMPLETE 400GRIT SANDING: 1 HOUR.


    -------------------------------------------------------------






    Now we move to wet sanding. Get a bucket of warm water and throw in some pieces of 1200 grit sanding paper. You might also get an old towel, fold it four times, and lay it on your lap. I found this greatly helps in not getting my lap soaking wet.

    awww.carpron.com_multisite_d_128684_1_IMG_2569.JPG

    Also, note that at this point, sanding can be done by hand for most parts. You're not altering the shape of the piece any more, you're just refining the texture of the aluminum. Some parts may still be easier to do with a block or rubber, but hand-sanding will get you into all the tight areas.

    TIME NEEDED TO COMPLETE 1200GRIT WET-SANDING: 45 MINUTES.


    -------------------------------------------------------------







    The last sanding step is 2500 grit. Again, this can be done by hand to save time. Finished piece:

    awww.carpron.com_multisite_d_128688_1_IMG_2581.JPG

    TIME NEEDED TO COMPLETE 2500GRIT WET-SANDING: 45 MINUTES.



    -------------------------------------------------------------







    Now it's time for the topping on the ice! Get yourself a hard cotton/cloth polishing disc with polishing paste (usually a hard bar), and mount it on a drill.

    awww.carpron.com_multisite_d_128692_1_IMG_2585.JPG

    Use this to polish the piece to the mirror-shine you always dreamed of!

    awww.carpron.com_multisite_d_128696_1_IMG_2590.JPG

    awww.carpron.com_multisite_d_128699_1_IMG_2593.JPG

    awww.carpron.com_multisite_d_128702_1_IMG_2598.JPG

    TIME NEEDED TO COMPLETE MACHINE POLISHING: 15 MINUTES.

    Now get polishing people!!
    awww.carpron.com_multisite_d_127616_2_IMG_2464.JPG awww.carpron.com_multisite_d_127621_2_IMG_2465.JPG awww.carpron.com_multisite_d_127624_2_IMG_2471.JPG awww.carpron.com_multisite_d_127627_2_IMG_2475.JPG awww.carpron.com_multisite_d_127630_2_IMG_2476.JPG awww.carpron.com_multisite_d_127636_2_IMG_2480.JPG awww.carpron.com_multisite_d_127642_2_IMG_2485.JPG awww.carpron.com_multisite_d_127645_2_IMG_2487.JPG awww.carpron.com_multisite_d_127654_2_IMG_2502.JPG awww.carpron.com_multisite_d_127657_2_IMG_2508.JPG awww.carpron.com_multisite_d_127660_2_IMG_2510.JPG awww.carpron.com_multisite_d_127669_2_IMG_2515.JPG awww.carpron.com_multisite_d_128663_1_IMG_2543.JPG awww.carpron.com_multisite_d_128667_1_IMG_2552.JPG awww.carpron.com_multisite_d_128670_1_IMG_2553.JPG awww.carpron.com_multisite_d_128676_1_IMG_2560.JPG awww.carpron.com_multisite_d_128680_1_IMG_2562.JPG awww.carpron.com_multisite_d_128684_1_IMG_2569.JPG awww.carpron.com_multisite_d_128688_1_IMG_2581.JPG awww.carpron.com_multisite_d_128692_1_IMG_2585.JPG awww.carpron.com_multisite_d_128696_1_IMG_2590.JPG awww.carpron.com_multisite_d_128699_1_IMG_2593.JPG awww.carpron.com_multisite_d_128702_1_IMG_2598.JPG
     
    #1
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  2. Mikey

    Mikey New Member

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    Awesome!

    I should polish up the head on the D16. hahaha
     
    #2
  3. Nachtmensch

    Nachtmensch New Member

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    may as well do the block and trans while youre at it :roflmao:
     
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  4. Nachtmensch

    Nachtmensch New Member

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    i just started this today on my intake manifold :spitdrink: :banghead:
     
    #4
  5. JussHatched

    JussHatched Active Member

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    Im trying this on a valve cover already too :) Saw a very similar tutorial on cb7tuner.com
     
    #5
  6. 2000CivicHatch

    2000CivicHatch New Member

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    awesome. i might try to pick up a spare mazda6 valve cover and polish it up. the guys on the mazda forum will be mind blown!
     
    #6
  7. Nachtmensch

    Nachtmensch New Member

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    :thumbup: post pics when youre done
     
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  8. CLUTCHONE
    Amazed

    CLUTCHONE Active Member

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    Great Thread...

    Damn It Came Out Friggin Chrome!!!!

    Im Gonna Try This on my Old Turbo... :eek:hsnap:
     
    #8
  9. Maikeru

    Maikeru New Member

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    I think I'll do this to my Miata's valve cover like every other Miata owner. lol.

    (...and the only reason I dig this back up is because it really should be stickied) ;) ...just sayin...
     
    #9

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