Also, the testing apparatus uses the rotation of a threaded rod to apply {HEAD ~ the force} necessary to create {TAIL ~ the face seal} 
necessary to create
Also , the testing apparatus uses the rotation of a threaded rod to apply { HEAD ~ the force } necessary to create { TAIL ~ the face seal }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL