Lapping seems to be a term that encompasses several different processes of similar nature.
I am interested specifically in the recommendations to lap the ways of lathes and mills. There seems to be a variety of ways people achieve this: From dedicated lapping compounds obtained in Auto part stores (which here nobody has heard of) to mixing up a scouring powder with oil to make a lapping paste. It brings up several questions:1) When does lapping stop and grinding starts (Permatex make a "valve grinding compound" which some people use for lapping)? 2) What is the maximum/minimum grit suitable for lapping? 3) Why isn't using ultrafine steel wool/Scotchbrite pad "lapping"?
FWIW I tried to make a 3/4" shaft turn more smoothly in bronze bearings. Not having anything "lapping-like" to hand I mixed up Fast Orange with oil and used that. It contains pumice and GOK what the grit of that is. The shaft is smoother. I think.
BTW it is now virtually impossible to get the old scouring powders for cleaning - everybody is so proud that their product is "scratch free".
While browsing in the Auto part stores I found several cleaning pastes which contain abrasives. Would they be suitable? Too harsh?