discussed above fig5 and 6 show the inventive coolant assembly 40 comprising a generally ring shaped configuration having a mounting adapter 42 a coolant header 44 and a retaining cap 46 the coolant assembly is preferably positioned attached to the end of the spindle housing 48 fig1 or 7 of the grinding wheel spindle 49 via the mounting adapter 42 by a plurality of screws 50 four are shown the coolant header 44 is positionable and rotatable about mounting adapter 42 retaining cap 46 is attached to mounting adapter 42 by a plurality of screws 52 one shown in fig6 to keep the coolant header 44 in position coolant header 44 is also rotatable about retaining cap 46 with the coolant assembly positioned attached to the spindle housing 48 as shown in fig7 one or more preferably four coolant nozzles 54 which extend from the coolant header 44 are positioned adjacent to the grinding wheel 8 coolant is supplied to the coolant header 44 via a feed pipe 56 alternatively coolant may be supplied through spindle housing 48 to appropriate channels extending through mounting adapter 42 and communicating with coolant header 44 changing the grinding zone position on the grinding wheel is accomplished by x direction movement in the machine of fig1 the present invention provides means to rotate.