Polishing Alum. Rims on Motorcycle

[RedBaron]

I would like to get some advise from you guys before I start my first polishing project. I have 2 motorcycle rims made from cast alum. that I have wet sanded down with 320, 400, 600, 1000 and 1500 sandpaper. They look great now but I'm ready to move on to the polishing stage. I have ordered a kit from caswell that will fit on my 4.5" angle grinder, I got the 8" wheels, I plan to slow the grinder down a little by the use of a reostate (variable resistor). My questions:

I plan to start with the black, but how long should I use this color, I know it depends on the work with sanding but wanted to get an idea for guide lines on each color, what to look for to move on to the next compound.

Will the angle grinder give me the results of a polished mirror finish?

Will the 8" wheels work with the angle grinder?

When completed I was looking at the Zoopseal, does this work and I read that it has a life span of 2 weeks while in the refrigerator, it this correct?

Ron

[mpierich]

You probably went a little farther than you had to with the sanding, but it can't hurt, at least.

Slow the grinder down more than a little, with 8" wheels.

Use each compound until it doesn't get any better, then move on. Clean well between steps and use a fresh wheel for each compound.

[FigureLLC]

if i recall properly, the recommended surface speeds for polishing aluminum are something like 3600-7500 surface feet per minute. figure it out like this:

C (surface length of wheel in feet (circumference)) = 3.14*D/12, where D is diameter of wheel.
RPM of motor should be marked on tool.
SFPM (surface feet per minute) = C*RPM

so for a 3600RPM motor, with an 8" wheel, you'd have
3.14*8/12*3600=7536 SFPM

i think this is right, but it's real early and cold.

also, i think varying the voltage to an a/c motor is a bad way adjust speed. i've done it before, but i'm learning more about a/c motors at the present, and i've read some things that said they don't work that way. i'm not sure what happens over time. like i said, i've done it (and to one motor i use on a daily basis).

[mpierich]

They make speed controls for inductive motors like the ones in modern grinders and routers. When I get around to it I'm going to get one for my die grinder. $20 - $30.

I don't think they're the same as rheoststs. You're right, I have heard that rheostats can burn out a regular AC motor.

[jrow]

RedBaron,

First off using an 8" angle grinder to get in between the spokes on a MC wheel is going to be a good trick. Now if you were to use a 3" - 4" wheel on a drill motor you would in all likely hood have and easier task.
Rule of thumb: If the aluminum is smooth and you can't catch the scratches with your fingernail just polish it! If you have scratches that you can catch with your fingernail sand/wet sand up to 400 grit.
Why? The black compound (Emory) is about 400 grit.
How long do you use the Emory, until it doesn't give you any higher luster, then switch to a new buff and use tripoli or white!
Clean your buffs ofter.
If you have sanded up to 1500 grit I would start with white compound on a sewn buff and see if that will give you the luster that you are looking for. If not back up to Tripoli on a sewn buff. Finish with white on a loose buff.
If you buy the Zoopseal kit you can mix as little as you want and save the rest for another project. Two weeks in the frig. AFTER MIXING is right. I use a little atomizer bottle to apply mine it works good.

John

[Maicojames]

guyd he must be polishing cast spoke wheels, as all other rims(spoke type) steel (Like Radelli etc) or Aluminum( Like Akront, Sun , DID, excel etc) are spun or stamped.

[RedBaron]

Thanks for your help guys, the polishing is working out great. I bought a small polisher (6") and really works nice, the adapter for the 4 1/2 grinder doesn't appear to polish the rims as nice as the polisher I bought.

[rides20]

That's a good call with the 6" buffer! I've polished many parts with the 6 incher that sears/craftsman puts out... I've since upgraded, but that'll certainly get you started!
You've come to the right place!