| 摘要 |
A screwdriver (by which term screwdriver drill bits and the like are included) which has an operative blade with an arcuate groove in each face adjacent the tip and forming, with the end face thereof, an acute angle, the groove extending across the entire blade width in each case and having a maximum depth chosen to provide, at the position of maximum depth of the grooves, a minimum thickness to the blade of between 75% and 95% of said thickness of the blade tip said position of maximum depth being located at a distance of from 40% to 100% of said blade tip thickness from the edge of the blade tip. |
