Twist drill
First Claim
1. A twist drill havinga shank,an axis of rotation about which the twist drill rotates during use, anda cutting tip, the cutting tip having a cutting edge which has an inner cutting portion forming a point having a point angle in the range 128°
- to 160°
, and a radially outer cutting portion that is inclined in the opposite axial direction to the inner cutting portion at an angle of from 2°
to 8°
with respect to a plane normal to the axis of rotation, said cutting edge being continuous over the inner and outer cutting portions and the outer cutting portion and the inner cutting portion abutting each other, the outer cutting portion being angled, relative to the inner cutting portion, such that the outer cutting portion leads the inner cutting portion in the rotational direction of cutting, the angle between the inner cutting portion and the outer cutting portion being in the range of being greater than 160° and
less than 180°
; and
the twist drill includes a cylindrical land and the outer cutting portion extends to the outermost edge of the cylindrical land.
1 Assignment
0 Petitions
Accused Products
Abstract
A metal-working twist drill is provided with inner cutting edges that form a point (18) having an angle, A, of 130°. An outer, peripheral, part of each cutting edge (55, 57) forms an outer cutting portion (59, 61). The outer cutting portions slope in the opposite direction to the corresponding inner cutting edges and form an angle B, of 3° with respect to a plane normal to the axis of rotation of the twist drill. The width of the outer cutting portion, D as measured at the cutting edge, is 10.5% of the diameter of the twist drill. The metal-working twist drill produces bores having a reduced exit burr height.
31 Citations
17 Claims
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1. A twist drill having
a shank, an axis of rotation about which the twist drill rotates during use, and a cutting tip, the cutting tip having a cutting edge which has an inner cutting portion forming a point having a point angle in the range 128° - to 160°
, and a radially outer cutting portion that is inclined in the opposite axial direction to the inner cutting portion at an angle of from 2°
to 8°
with respect to a plane normal to the axis of rotation, said cutting edge being continuous over the inner and outer cutting portions and the outer cutting portion and the inner cutting portion abutting each other, the outer cutting portion being angled, relative to the inner cutting portion, such that the outer cutting portion leads the inner cutting portion in the rotational direction of cutting, the angle between the inner cutting portion and the outer cutting portion being in the range of being greater than 160° and
less than 180°
; andthe twist drill includes a cylindrical land and the outer cutting portion extends to the outermost edge of the cylindrical land. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
- to 160°
-
12. A method of drilling a hole in a laminate material comprising fiber-containing and metal-containing layers, in order to minimize fraying and splintering of the fiber-containing material and to further minimize hole erosion and excessive tool wear, comprising the steps of:
-
forcing a drill into the laminate, which drill has a cutting edge which has an inner cutting portion forming a point having a point angle in the range 128°
to 160° and
a radially outer cutting portion that is inclined in the opposite axial direction to the inner cutting portion at an angle of from 2°
to 8°
with respect to a plane normal to the axis of rotation, wherein said cutting edge is continuous over the inner and outer cutting portions and the outer cutting portion and the inner cutting portion abut each other, the angle between the inner cutting portion and the outer cutting portion being in the range of being greater than 160° and
less than 180°
,the initial entry of the drill being in a fiber-containing layer such as to minimize fraying and splintering thereof and said drill subsequently drilling through a metal-containing layer and subsequently passing through an exit hole of the laminate material. - View Dependent Claims (13, 14, 15, 16, 17)
-
Specification