The processing process of {HEAD ~ the recessed hole} in the box end of {TAIL ~ the wrench} is also complicated  
The processing process of { HEAD ~ the recessed hole } in the box end of { TAIL ~ the wrench } is also complicated
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH