I've read many times about the need to cover the ways when grinding on the lathe, to prevent grinding dust from harming the machine.
Is this also true when using emery cloth for finishing?
Yes. Pretty much any grit or dust that can mix with the oil and start wearing away at your machinery should be avoided. This includes grit/dust from abrasives (including bench and angle grinders used in close proximity), cast iron swarf etc.
Essentially, you don't want to be applying valve grinding paste to your ways!
hi just my bit do not use anything that contains diamond IE files or polish with out all bin covered up well as once it gets embedded in to cast iron and it will never cum out unless you intend to have the bade reground