lives autotrapanante and automaschiante

摘要

The fastener has a threaded shank (112) and a pilot end (116), which is generally elliptic in transverse section, to accomplish the drilling process. The pilot end (116) comprises a pair of flutes (118, 119), each of which has a cutting surface (120, 128) which has generally along the major axis of the ellipse, a transverse drag surface (140, 142) which is formed arcuately in the longitudinal direction and is of substantially constant radius (R) along its length to provide clearance for chips of material produced by the drilling process. The cutting surface (120, 128) may also be formed longitudinally arcuate to provide the correct rake for drilling. IMAGE