In general, a friction test machine according to the invention comprises {TAIL ~ a sample holder} configured to hold a sample in frictional engagement with a friction surface, and a motion device for effecting relative movement between {HEAD ~ the friction surface} and sample holder in a first direction 
In general , a friction test machine according to the invention comprises { TAIL ~ a sample holder } configured to hold a sample in frictional engagement with a friction surface , and a motion device for effecting relative movement between { HEAD ~ the friction surface } and sample holder in a first direction
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH