# Best way to sand & polish copper alloys?



## Handlobraesing (Jan 15, 2007)

What is the easiest and fastest way to sand and polish out embossed and incised bronze or brass type metal to give a smooth, mirror finish, such as machining pre-1982 pennies to smooth copper disk to be used as a heat spreader? 

I'm mainly interested in pure copper, brass, nickel silver, and maybe aluminum.

Coarse grit paper takes away the incision fast, but it leaves streaks that takes a long time to polish out, so I would use finer paper, but it takes a long time to take out the incision/embossing.


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## PhotonFanatic (Jan 15, 2007)

There are no shortcuts when it comes to sanding and polishing those metals to a shiny, scratch-free surface.

You start with coarse grit wet/dry sandpaper and progress through the grits until you have a fairly shiny surface just from sanding; then you go to the polishing compounds and do the same thing with those, i.e., progress from coarse (Tripoli, say) to very fine (Rouge).

Unless you follow that routine, what you would otherwise end up with is just a nicely polished, but scratched surface--looks good from a distance, but ugly up close.


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## chimo (Jan 15, 2007)

Start by flattening the high points with hammer/anvil. Then sand. That will cut the amount of time required a bit.


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## lukus (Jan 15, 2007)

Hot glue the penny to a 3 or 4 inch piece of dowel stick. That will give you an easy to hold handle and make the sanding much easier. Stick the sandpaper to a piece of glass with water. Keeping it wet with some water and a drop or two of liquid dishwashing detergent and it will cut quicker. 

I would start with 220 and knock off most of it; then 320 and 400. Let the 400 paper load up and you'll get a pretty good polish. If you have 600, even better.


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## bwaites (Jan 15, 2007)

First of all, unless you are using OLD pennies, they aren't anywhere close to pure copper. You can get copper slugs (or copper sheeting) at most hardware or metal stores, so you'd be better off doing that for your heat sinks.

If they don't have slugs, then most metal shops have a punch machine that can make them fairly cheaply.

The slugs won't have the embossing, so you can polish them quite a bit faster.

Bill


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## VidPro (Jan 15, 2007)

dremmel? if you dont have a Lathe for round stock, and want to speed up the polishing aspect a dremmel has worked for me.
grind with 400 , then 800, then mabey 1000, then there is a dremel tip that has a cloth head, its like a stack of round rags sewn together about 1.5in in diameter, with Scotch scratch remover (compound wax) and it flinging around bits of wax and fabric , it sure saved time.

if i was doing pennies, it would be the belt sander and nicked fingers first


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