The grinding wheel of the first wheel head, which has its home position at {HEAD ~ one end} of {TAIL ~ a common path}, initially grinds the object portion which is located far from the home position; i.e., the object portion which is located near the other end of the common path, at which the home position of the second wheel head is located 
The grinding wheel of the first wheel head , which has its home position at { HEAD ~ one end } of { TAIL ~ a common path } , initially grinds the object portion which is located far from the home position ; i.e. , the object portion which is located near the other end of the common path , at which the home position of the second wheel head is located
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH