Need mirror finish electroless nickel plating on inner walls of holes

A. Electropolishing has its limitations when it comes to removing grooves and deep scratches. The only thing I could suggest is to address the drilling and countersink methods. The better the fabrication process is, the easier it is for you in the plating process. Good sharp drill bits, correct drill speeds and stack height (if stack height is applicable). I have also seen polishing tips employed in the same drill program used for the parts. Good Luck!

A. Most plating processes, with few exceptions reproduce the substrate as is. What you need to attain, if achieved in a chemical way, would be known as "leveling" and is mostly done by the plate like in bright nickel plating or selectively removing metal around scratches and valleys like in electropolishing (EP). Unfortunately due to your geometry and substrate, bright nickel or EP are limited. In my opinion, you need to improve the hole surface before plating. For that purpose, there are several approaches, lapping, honing, burnishing or vibratory bulk finishing. You may have to add an intermediate finishing step before the final plate.