As I indicated in my original posting the variance that I am currently
getting is .00018" in the longitudinal direction and .00046" in the
transverse direction. These are the worst case variances. Some areas
are significantly better. In regard to coolant the K.O. Lee Rep
advised that I should get satisfactory results with mist coolant. Some
books I have read state that in many instances it is easier to obtain
proper cooling from a mist setup than it is from a normal flood setup.
Grinding wheels are porous and act as a fan. The wheels produce a thin
layer of air around the periphery of the wheel that forces liquid
coolant away from the wheel and starves the grinding contact point.
Special flood coolant nozzles have been designed specifically for
grinding to essentially scavage this air layer and allow the coolant to
get to the contact point. Most grinders do not have this special
nozzle. Because a mist system is pressurized it is fairly simple to
direct the spray directly at the contact point. The bulk of heat is
obviously generated at the contact point. Mist systems provide very
effective evaporative cooling which from what little physics I can
remember is a very effective heat transfer mechanism. The downside of
mist systems is that they provide little lubrication. It is my
understanding that this lack of lubrication is a surface finish issue,
not a cooling issue. Because in many grinding operations surface
finish is important, flood systems are popular.