The auger flights are formed from a flange that is helical around the central shaft and {HEAD ~ the direction} of rotation of the helix may reverse at {TAIL ~ a selected point} on the tube 
The auger flights are formed from a flange that is helical around the central shaft and { HEAD ~ the direction } of rotation of the helix may reverse at { TAIL ~ a selected point } on the tube
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH