[Rasper]

There are too many factors involved that I don't know. It is best to post a photograph of what you want to polish so we can see what we are dealing with. Such things as: is the frame marred up, painted, etc.?

Be very careful using any circulating power sander, like flap wheels, on aluminum. It is so easy to gouge it beyond repair. Tubing is best sanded by hand. The direction of motion doesn't matter; just get it smooth with out gouging it.

Stainless is another thing entirely. It is so hard that you must use a power sander, if it needs sanding at all. Most bike exhausts are already polished pretty well. There again, post some pics so we can see what we are dealing with.

Richard