need help polishing aluminum

[fxstcguy98]

I am having some serious problems trying to polish an aluminum derby
cover. I am useing a 6" bench grinder with 8" spiral sewn buff and
caswells black. Whenever I make a pass it leaves dull black streaks
one each side of the pass. If I press real hard, it leaves scatches.
I raked the buff before I started and applied compound often. I
don't know if I am using too much pressure, not enough, moving to
fast or slow, or if I don't have enough rpms on the buffer. See pic below, you can see the streaks running vertical in the picture, it's hard to see them because of the clouds reflecting on the part. Feedback please.
Darrin
ok when I figure out how to attach a pic I will get back to you.

[fxstcguy98]

I put the pic under metal polishing file name fxstcguy98

[Stale]

I'm a rookie at this, but isn't 8" a little big for a bench grinder ? Did you try a smaller wheel ? I use 8" and 10" wheels myself but my machine looks like this:

[clydes]

wow ! thats a polshier. clydes

darby covers are a pain some time's and they can be polished to a high gloss. the metal they use is soft and some time is is cheaper to have plated ... + it save you time

[fxstcguy98]

I aware that I can buy a derby for $5 or $10. This is the first piece of aluminum that I am trying to plate. I need to learn how to plate alum, but first I need to learn how to polish it. I polished steel and copper sucessfully, now I am on alum, and next is potmetal, God help me.