I,m about to finish fabbing a copper prototype part. I was wondering what is a good way to get a good true flat polished surface? I plan to get a vibratory polisher in the future but for the prototype I,ll have to hand polish it. Would wool or wet sand paper be the way to go. And what is tripoli? ANd how is it used?

Finer and finer grits of paper followed by "gray" then "white" Scotch Brite. I've used white to take out minor scratches in furniture.

Finally, a product called Brasso used to be available for polishing copper sauce pans.

Jeweler's rouge and a felt wheel should ultimatelymake it really shiney.

tripoli is a buffing compound, aluminum silicate abrasive that you apply to a spinning buffing wheel. tripoli is the right stuff for copper. You can bring any metal to a perfect mirror finish with wet dry paper used wet (or it clogs too quickly), you'll find the finest grits at autobody supply places. I find fastest is file ...wet/dry 200... wet/dry 600 ...then either w/d 2000 or buffing wheel and you're optical

if flatness is important do it on the surface plate - polishing/sanding is not a precision op though so at some level of magnification what you produce will be slightly convex surface

Thanx I,ll give em both a try if I have to.

Just hand lapping on piece of glass or flat surface with sand paper on top while keeping bit of water through... 100 grit, 200grit, 500 grit, 1200 grit, (and you can go 2000... but nah...)
Get your buffing wheel up and use tripoli and go around a little... this is what you get mirror for. I need better way to do this than hand though... consumes too much time.

Must be a US thing. We still have Brasso over here in almost every general store. Its for brass mainly, but I suppose it would probably shine copper aswell, says so on the tin! Chemistry aint my strong point. There's also 'Silvo' for silver specifically, but would probably work on some other silver coloured metal, but from personal experience, not all.

http://www.britsuperstore.com/cgi-bin/sh000001.pl?REFPAGE=http%3a%2f%2fwww%2ebritsuperstore%2ecom%2facatalog%2fSilvo_Silver_Polish%2ehtml&WD=brasso&SHOP=%20&PREVQUERY=SS%3dbrasso%26PR%3d%2d1%26TB%3dA%26SHOP%3d%20&PN=Brasso%2ehtml%23a2002#a2002
http://www.britsuperstore.com/acatalog/Silvo_Silver_Polish.html

Don't bother going through too many grits...

Start with maybe 80 grit to remove the big scratches - sand until they are all gone and only sanding marks remain. They go to 120, 240, 320 and 400. Go wet on the 320 and 400... after the 400, it will be a matt finish with no shine. then get a spiral sewn wheel and tripoli and buff it with that and it will be semi-gloss, but pretty shiny. Then get a loose sewn butting wheel and white jewelers rouge. After you polish with that, it will be like a mirror.

If its not badly scratched to start, you could start at 120 grit or maybe even 240-something grit.