Multiple rake drill bits
First Claim
1. A twist drill bit comprising;
- A. a shank adapted to be rotatably driven, and b. a longitudinally elongated drill body which protrudes coaxially forward from said shank, said body having (i) a tip which tapers forward to a point, and (ii) at least a first flute formed in said body and disposed longitudinally rearwardly from said tip, said flute having a first longitudinal portion inclined at a first rake angle with respect to a longitudinal axis of said body, and a second longitudinal portion inclined at a second rake angle with respect to said longitudinal axis of said body, said body having formed therein adjacent to said flute a land having a longitudinally disposed cutting lip having a first longitudinal portion inclined at said first rake angle relative to said longitudinal axis of said body, and a second longitudinal portion inclined at said second rake angle relative to longitudinal axis of said body.
0 Assignments
0 Petitions
Accused Products
Abstract
A dual rake twist drill bit for drilling holes in articles made of abrasive materials, such as fiberglass-filled printed circuit boards, which relatively quickly dull bits, has a conical point and a short front cutting portion in which is formed spiraled flutes having cutting lips which are inclined to the axis of the bit at a relatively small helix angle or rake in the range of about 3 degrees to 10 degrees, and a longer rear portion in which the flutes and cutting lips have a larger rake of about 33 degrees. The dual rake bit has substantially greater wear resistance than single rake bits. In a modification of the dual rake bit, the central web portion thereof has a front longitudinal portion which is relatively acutely tapered, and a rear portion which is relatively modestly tapered, the dual tapered construction increasing resistance of the bit to breaking.
60 Citations
58 Claims
-
1. A twist drill bit comprising;
-
A. a shank adapted to be rotatably driven, and b. a longitudinally elongated drill body which protrudes coaxially forward from said shank, said body having (i) a tip which tapers forward to a point, and (ii) at least a first flute formed in said body and disposed longitudinally rearwardly from said tip, said flute having a first longitudinal portion inclined at a first rake angle with respect to a longitudinal axis of said body, and a second longitudinal portion inclined at a second rake angle with respect to said longitudinal axis of said body, said body having formed therein adjacent to said flute a land having a longitudinally disposed cutting lip having a first longitudinal portion inclined at said first rake angle relative to said longitudinal axis of said body, and a second longitudinal portion inclined at said second rake angle relative to longitudinal axis of said body. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
-
-
21. A twist drill bit comprising;
-
a. a longitudinally disposed, generally cylindrically-shaped shank, said shank adapted to be insertably and coaxially received by a collet and rotated about a longitudinal axis of said shank, and b. a longitudinally elongated, generally cylindrically-shaped drill body which protrudes coaxially forward from said shank, said body having formed therein, (i) a generally conically-shaped tip, and (ii) a pair of first and second flutes formed in circumferentially spaced apart locations in a cylindrical wall surface of said body, each of said flutes having a first longitudinal portion inclined at a first rake angle with respect to a longitudinal axis of said body, and a second longitudinal portion inclined at a second rake angle with respect to said longitudinal axis of said body, said body having formed therein adjacent to said flutes a pair of lands each having a longitudinally disposed cutting lip which has a first longitudinal portion inclined at said first rake angle relative to said longitudinal body axis, and a second longitudinal portion inclined at said second rake angle relative to said longitudinal axis of said body. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
-
-
34. In a twist drill bit having a cutting portion which includes a longitudinally elongated, generally cylindrically-shaped body having a tip which tapers to a smaller diameter, and at least a first longitudinally disposed flute formed in said body and forming on opposite circumferential sides of said flute a land, one longitudinal edge of which serves as a cutting edge or lip for cutting material from an article to form therein a hole when said tip is pressed against a surface of said article and said bit is rotated about a longitudinal axis of said body in a direction from said cutting edge towards said flute, the improvement comprising;
said cutting edge having a first longitudinal portion inclined at a first, small rake angle with respect to said longitudinal axis of said body, and a second longitudinal portion inclined at a second, larger rake angle with respect to said longitudinal axis. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49)
-
50. In a twist drill bit having a cutting portion which includes a longitudinally elongated, generally cylindrically-shaped body having a tip which tapers to a smaller diameter, and at least a first longitudinally disposed flute formed in said body and forming on opposite circumferential sides of said flute a land, one longitudinal edge of which serves as a cutting edge or lip for cutting material from an article to form therein a hole when said tip is pressed against a surface of said article and said bit is rotated about a longitudinal axis of said body in a direction from said cutting edge towards said flute, the improvement comprising;
a web having at least two different tapers. - View Dependent Claims (51, 52, 53)
- 54. In a twist drill bit, the improvement comprising a central longitudinally disposed web having at least first and second longitudinal portions having first and second tapers, respectively.
Specification