Metal finishing: what's a "nice" waviness spec for a grinding shop?

Factual Questions
1

I know, it depends. I’m having some stainless plates ground to 8 microinches Ra for use in testing thermal conduction in various engineering plastics coming in contact with the plates. In my opinion 8 microinches is a nice smooth ground finish, but it’s not one that would be surprising or obscure in a typical machine shop or grinding shop. I think any shop that advertises they do industrial grinding would accept my order. But if I said 1 or 2 or maybe 4 microinches they’d say that had to be lapped or polished and maybe it would be a special thing I’d have to find a specialty shop for.

What I want to know is, what value of waviness is similarly at the nice end of what a grinding shop can do, but not obscure or special?

I don’t know what level of waviness or roughness is “required”. I’m a scientist studying this question, and what I lack is a feel for, or experience with, what’s practical to do with typical shops.

Thanks!

2

I think you need to think in terms of 2 specs: Ra, which is the texture on the surface, and flatness, which is the contour of the surface.

3

Your best bet is to ask your vendor (or potential vendor). Particularly if you don’t have a good grasp on your requirements. It is unlikely a vendor would recommend requirements outside of their capabilities, and they may ask questions you hadn’t considered.