"Ricky Wang" <RickyWang@has.none> wrote in message
news:jJqSg.5123$TV3.3285@newssvr21.news.prodigy.co m...
>
> A near mirror finishes are too expensive for the average car owner
> could afford. Unless the car manufacturer requires a near mirror
> finish, don't bother with it.
>
My retired ex-partner has done some milling for me in his garage, and the
output of the milling machine can be described as "near mirror finish." If a
milling machine isn't producing that sort of output, it's because the head
hasn't been dressed lately. That's the sort of neglect that can weaken the
head gasket seal as combustion gasses insinuate their way through the gaps.

Actually, I don't think debris produces the milling marks. The cutter head
is an abrasive disk spun at high speed that is scanned across the surface in
the plane of the disk The edge of the disk cuts a flat groove at a preset
thickness, then is moved laterally to cut an identical groove beside that,
and so on. Milling marks appear if the wheel edge is not true.

Mike