Hi, I'm new to the forum.
Years ago I found a handy chart where it stated the average surfaces finish by the tolerance of the feature. I've been looking in the internet, but I can't find any such chart again. Everything I'm seeing on the internet is finish range by a machining process. An example of what I'm looking for is:
±.005 = 125 RMA
±.001 = 64 RMA
±.0005 = 32 RMA.
These are not the actual values, but rather my best guess. I was looking for a chart to validate.
Surface finish and surface size or form are not inter-changable.
One can have an Ra of 250 micro inches and a flatness of .0002".
Ra of 8 microinches and a surface size variation of +/- .040"
Surface roughness is independent of form and size and are NOT interchange-able - ever..,
Tell me and I forget. Teach me and I remember. Involve me and I learn.