Improvements in or relating to engineers' taps and drills

摘要

696,833. Taps; drills. BASTIEN, R. Feb. 18, 1952 [Nov. 17, 1950; June 15, 1951], Nos. 28159/50 and 14171/51. Class 83 (iii). A tap has two straight or spiral flutes 7 which leave two wide threaded portions 4 on which relief is provided by removing all or a portion of the thread centrally between the cutting and trailing edges to form a flat 8 merging gradually into the cutting and trailing edges. The tap may be combined with a drill 1 having similar relief on the lands 2. The first Provisional Specification describes also a relief provided by centrally reducing the top, sides and bottom of the thread without altering the thread form.