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Need better than a Mirror Finish on Metal

February 17, 2011

I need to get a highly polished finish on a tool surface that is slightly domed (1m x 1m x 0.1m). The surface roughness requirement is RMS = 1nm (1 nanometer = 0.04 microinch) RMS or Ra = 0.90nm (0.036 microinch). Yes, this is a small number. The overall surface figure for the tool is RMS = 25 microns so this is more of a local smoothness issue. So the question is what is the best way to get there?


1) What material is the best to use? (aluminum 6061 is probably the softest material we would consider)

2) What roughness should we machine the surface to?

3) What setup should we use to polish? CNC or can this be done by hand?

4) What polishing steps are required?


Here is a solution for 301 Stainless Steel ( www.finishing.com/453/66.shtml )
0) Start with a piece of raw 12 gage plate
1) Sand out all defects with a 90 deg hand sander using 180 grit disk pad.
2) Go over entire part with Trizact A45 using hand drum sander.
3) Go over entire part with Trizact A16 using hand drum sander. (90 deg to last cut)
4) Go over entire part with Trizact A6 using hand drum sander. (90 deg to last cut)
5) Go over entire part with Nuvite F9 polishing compound. (Make sure ALL defects are out.)
6) Finally go over entire part with Nuvite Grade A polishing compound.

My guess is this is probably far from the Ra number I'm looking for but probably a good start.

Thank you for your input.

Mark Pryor
Engineer - San Diego, California, USA