Assertion: phillips screwdriver's head | /r/HasProperty | weakened
Facets:
Source sentences:
text: His patent describes the major advantages: It is well known to persons who use screws that if the nicks are narrow and shallow it is difficult to drive the screw without the screw driver slipping out of the nicks, and if the nicks are wide and deep to afford a good gripe, the head of the screw is weakened, and the screw-driver is liable to slip out sidewise and deface the finished surface of the work, and if the screw-driver is the same width as or wider than the head of the screw, the countersink work is liable to be defaced, and the angles of the screw-driver are often broken.