Features: BSF - British Standard Fine; This thread form was based upon the British Standard Whitworth (BSW) but has a finer thread (more threads per inch for a given diameter). ; The thread form was first introduced in 1908 and is specified in BS84:1956. ; When used on external threads this series has greater tensile stress area than coarse threads of the same size. ; Fine series threads will resist stripping out better than coarse threads in areas where the external and mating internal threads are subjected to loads equal to or greater than the capacity of the screw or bolt. ; Fine threads are also used where the length of engagement is limited or where wall thickness demands a fine pitch. ; TAPER TAPS have a lead of eight threads and are used as a starting tap in difficult or high precision holes. ; Manufactured from HSS this general purpose tap is designed for use in medium tensile materials and is for hand or general machine use. ; Specifications:Diameter5/16"Pitch22 tpiLeadingTaperOverall Length72 mmTapping Drill6.8 mm