Improvements in or relating to Screw Fastener Assemblies

摘要

1,167,016. Self-tapping screws. PARKERKALON CORP. 3 Nov., 1966 [3 Nov., 1965], No. 49249/66. Heading B3N. [Also in Division F2] A self-tapping screw 20 in which the underside 23 of the head is of spherical form.