Twist drill and method for producing a twist drill which method includes forming a flute of a twist drill

摘要

There is now provided a twist drill and a method for producing a twist drill which method includes forming a flute of a twist drill. The drill has drill material and a tip portion with a cutting lip. The drill has a land structure and a flute to remove chip residue. The land structure has a flute wall and a cutting edge structure that is disposed longitudinally along the flute wall. The cutting edge structure has a first portion at the drill tip portion and a second portion disposed away from the drill tip portion. The flute wall extends further into the land structure at the second portion of the cutting edge structure than at the tip portion to provide a greater amount of drill material at the tip portion than at the second portion of the cutting edge structure. The flute wall extends further into the land structure at the second portion of the cutting edge structure than at the tip portion to provide a greater flute volume per length at the second portion of the cutting edge structure than at the drill tip portion. The method provides for forming a drill with a grinding tool to form different angular transitions of the cutting edge structure.

主权项

1. A method of making a twist drill from a drill blank; said twist drill having a longitudinal axis about which said drill is configured to rotate during use; said twist drill comprising: a plurality of main cutting edges disposed at a tip portion, said main cutting edges being connected to one another by a chisel edge; said main cutting edges being disposed to run rectilinearly toward said chisel edge; a plurality of secondary cutting edges, each being disposed adjoining a corresponding one of said main cutting edges; a plurality of flutes being configured and disposed to permit removal of chips produced during drilling; each of said secondary cutting edges being disposed to run along a corresponding one of said flutes in the direction of the longitudinal axis of said drill; each of said flutes comprises a flute wall portion which extends from a corresponding secondary cutting edge substantially toward the longitudinal axis; each of said secondary cutting edges having a plurality of secondary rake angles (γ) at points along the length thereof, which secondary rake angles (γ) are defined by a tangent of said flute wall portion perpendicular to the longitudinal axis and a radial line perpendicular to the longitudinal axis, and which secondary rake angles (γ) increase along the length of said secondary cutting edges in a direction away from said tip portion; said method comprising the steps of:
forming a first rectilinear main cutting edge by grinding said drill blank; forming a first flute and a first secondary cutting edge corresponding to said first main cutting edge by grinding said drill blank and removing increasing amounts of drill material along the length of the drill blank to form a first plurality of secondary rake angles (γ) which increase along the length of said first secondary cutting edge in a direction away from said tip portion while maintaining the twist drill to have a constant diameter (D) along the length thereof; performing the above steps for at least one additional main cutting edge and its corresponding flute and secondary cutting edge, and forming the twist drill to have a core diameter that remains constant in a longitudinal direction of the twist drill.