Drill bit of the twist drill type
AssigneeEmhart Inc.
InventorWalter Schimmer
Life of this patent
Estimating the term…
Abstract
Drill bit of the twist drill type with turns which are held together by a drill center web and each issue in a radially extending cutting edge of which one extends to the bit axis and the other is shorter than it. This is characterized by the following features: a) the cutting edges (2,3) formed by continuos straight edges lie essentially in a plane coinciding with the bit axis (9), b) the cutting edges (2,3) form an obtuse angle (cutting angle), lying below 180.degree., of at least 175.degree., c) the cutting edges (2,3;16) having a leading edge angle (K) of about 30.degree. with a rake angle (S.sub.1, S.sub.15) of about 30.degree. to 45.degree., d) the diameter (D) of the drill center web (6) is at most half the bit diameter.
Claims9
A rotary drill bit adapted for high speed drilling of a blind counterbore having a substantially flat to slightly concave floor in a metal workpiece, said bit having a central bit axis and a bit diameter and comprising
- a shank;
- a center web extending from said shank along said bit axis toward a drilling end;
- at least one helical turn extending around and along said center web, said turn having a front surface facing in the direction of rotation of said bit and a free face at the end thereof;
- said front surface and said free face forming a cutting edge therebetween, said cutting edge having a leading edge angle defined by said front surface and said free face;
- said cutting edge being formed in a straight line beginning at said bit axis and extending outwardly therefrom and lying in a common plane with said bit axis, the angle between said cutting edge and said bit axis being from 87.5.degree. to 90.degree.;
- and
- the maximum dimension of said center web in a plane perpendicular to said bit axis being less than one-half of said bit diameter.
A rotary drill bit adapted for high speed drilling of a blind counterbore having a substantially flat to slightly concave floor in a metal workpiece, said bit having a central bit axis and a bit diameter and comprising
- a shank;
- a center web extending from said shank along said bit axis toward a drilling end;
- a pair of helical turns extending around and along said center web, each turn having a front surface facing in the direction of rotation of said bit and a free face at the end thereof;
- said front surface and said free face on each of said turns forming a cutting edge therebetween, said cutting edge having a leading edge angle defined by said front surface and said free face;
- each of said cutting edges being formed in a straight line extending outwardly and lying in a common plane with said bit axis, the angle between said cutting edges and said bit axis being from 175.degree. to 180.degree.;
- one of said cutting edges extending inwardly to said bit axis;
- and
- the maximum dimension of said center web in a plane perpendicular to said bit axis being less than one-half of said bit diameter.
A rotary drill bit adapted for high speed drilling of a blind counterbore having a substantially flat to slightly concave floor in a metal workpiece, said bit having a central bit axis and a bit diameter and comprising
- a shank;
- a center web extending from said shank along said bit axis toward a drilling end;
- at least one helical turn extending around and along said center web, said turn having a front surface facing in the direction of rotation of said bit and a free face at the end thereof;
- said front surface and said free face forming a cutting edge therebetween, said cutting edge having a leading edge angle defined by said front surface and said free face;
- said cutting edge being formed in a straight line beginning at said bit axis and extending outwardly therefrom and lying in a common plane with said bit axis, the angle between said cutting edge and said bit axis being from 87.5.degree. to 90.degree.;
- the maximum dimension of said center web in a plane perpendicular to said bit axis being less than one-half of said bit diameter;
- and
- a rake angle being defined between said front surface of said turn and said bit axis, said rake angle lying between 30.degree. and 45.degree. at the exterior edge of said bit and diminishing continuously from the exterior inwardly to an angle of 0.degree..
A rotary drill bit adapted for high speed drilling of a blind counterbore having a substantially flat to slightly concave floor in a metal workpiece, said bit having a central bit axis and a bit diameter and comprising
- a shank;
- a center web extending from said shank along said bit axis toward a drilling end;
- at least one helical turn extending around and along said center web, said turn having a front surface facing in the direction of rotation of said bit and a free face at the end thereof;
- said front surface and said free face forming a cutting edge therebetween, said cutting edge having a leading edge angle of 30.degree. defined by said front surface and said free face;
- said cutting edge being formed in a straight line beginning at said bit axis and extending outwardly therefrom and lying in a common plane with said bit axis, the angle between said cutting edge and said bit axis being from 87.5.degree. to 90.degree.;
- and
- the maximum dimension of said center web in a plane perpendicular to said bit axis being less than one-half of said bit diameter.
Dependencies are inferred from the claim text.