Twist drills
AssigneeDormer Tools (Sheffield) Limited
InventorsBertram Victor Howarth, Richard Goodwin
Life of this patent
Estimating the term…
Abstract
A helical twist drill has fluted lands each having projecting from their radially outer faces a plurality of circumferentially spaced support margins. At least one of the support margins is asymmetrically spaced with respect to the other support margins.
Claims9
A twist drill comprising a generally cylindrical drill body, a plurality of circumferentially spaced helical flutes extending along said body and fluted lands alternating with said flutes, the drill body having a leading end to which said flutes and fluted lands extend, the fluted lands forming radially outer faces on the drill body, a plurality of circumferentially spaced support margins projecting from the radially outer face of each said fluted land, at least one of said support margins being asymmetrically spaced with respect to the other support margins-of the drill circumferentially of the drill body.
Dependencies are inferred from the claim text.