{HEAD ~ The heat hardening process} may be individually controlled for {TAIL ~ each spring}, and it may be performed in a very short period of time 
individually controlled for
{ HEAD ~ The heat hardening process } may be individually controlled for { TAIL ~ each spring } , and it may be performed in a very short period of time
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH