Patrick Chase
Derek's suggestion of using 180# CBN wheels brings up a key difference between CBN and traditional wheels.

When you grind a piece of metal, there are two major sources of heating:

1. Heat dissipated due to deformation of the metal that is removed. To a rough first order this is proportional to the total volume of metal removed.

2. Surface friction between the abrasive and the workpiece. To a rough first order this is proportional to the number of revolutions the grinding wheel takes to get the job done, and inversely proportional to the sharpness of the abrasive.

Fine grit wheels require more revolutions/passes to remove a given amount of material and therefore dissipate more heat into the tool from friction. That's why you generally want to do major material removal using coarse grits with conventional (AlOx) wheels.

CBN crystals are sharper and cut more easily than AlOx grains (especially worn ones) and vastly reduce frictional heating. That in turn means that the "heat penalty" of finer grit wheels is greatly reduced, and you can get away with doing significant grinding on 180# or 220#.

As to the amount by which CBN reduces heating, I've seen one study showing a 4X reduction, though I can't remember what grit # it was for. Deformation heating is relatively constant, so obviously CBN does best compared to conventional wheels when friction dominates, i.e. at finer grits.