{HEAD ~ The crusher} replaces {TAIL ~ the drilling machine} upon completion of the drilling of a guide hole by the drilling machine 
replaces
{ HEAD ~ The crusher } replaces { TAIL ~ the drilling machine } upon completion of the drilling of a guide hole by the drilling machine
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