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?

--
Michael Koblic,
Campbell River, BC