a locking assembly to frictionally lock {HEAD ~ the breastplate} to {TAIL ~ the shaft} at at least one arced groove 
to
a locking assembly to frictionally lock { HEAD ~ the breastplate } to { TAIL ~ the shaft } at at least one arced groove
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH