As far as I know, the general metal surface processing technology can't reach Ra0.02. Is it wrong? It seems to be Ra0.2? For example, rolling, polishing and milling, which can improve the surface roughness, can not achieve this effect. As far as I know, the best way to do it so far is Hawker Machining, which is a new mirror machining technology invented by a company called Shandong Huayun. There is no problem that they can achieve Ra0.05.

If it must reach Ra0.02, it can only be electroplating, but I don't know if electroplating is cost-effective for you, hehe, that's all, you have to give points, dear.