oh, I got my info from here.....

http://www.dsmtuners.com/forums/articles-engine-fuel/303225-engine-machine-work-explained.html


"Another machine is the surface grinder, not a bad machine, it keeps the head leveled and indexed, it uses segmented stones. The surface finish is not smooth enough most of the time for MLS gaskets, The finish is dependent on what stones, how well dressed they are, spindle speed and table speed. Still very common in shops

The new boy on the block is a High speed Milling machine, these use a .500 (1/2) inch insert, CBN for cast Iron and CBN for alum. for the most part, as far I as know, have been around about 10 years. smaller shops are slow on getting them due to there cost, But without a doubt give the best surface finish. Some machines, Like the comec I use, have variable rate spindle speed and variable rate table feed rates. This will alow for diffrent surface finishes for diffrent gaskets"