Metal tools and implements – making – Blank or process – Drill
Reexamination Certificate
1998-08-26
2001-02-06
Rada, Rinaldi I. (Department: 3724)
Metal tools and implements, making
Blank or process
Drill
C076S101100, C076SDIG001, C408S145000
Reexamination Certificate
active
06182533
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of making a drill blank and more particularly a micro-drill blank.
In the manufacture of various products, particularly printed circuit boards, it is necessary to form a plurality of small holes therein. These holes are generally formed by means of a small diameter twist drill or micro-drill. Since such boards are abrasive, for example made of fibre reinforced plastic, it has been found that drill bits tipped with diamond abrasive compact are particularly suitable.
Various methods have been described in the literature for producing micro drills. EP 0 206 652 describes a method of producing a blank for a drill bit comprising providing a composite abrasive compact having a diamond or cubic boron nitride compact bonded to a cemented carbide backing and having major surfaces on each of opposite sides thereof, severing the composite abrasive compact along planes perpendicular to the flat surfaces and from one flat surface to the other to produce a plurality of sticks polygonally-shaped end-on, each severed plane defining side surfaces of adjacent sticks and longitudinally rounding each stick to produce from it a blank for a drill bit which is round end-on. The drills may be made by fluting the rounded stick.
EP 0 223 474 describes a method of making a drill blank comprising a cylindrical carbide body having a vein of abrasive compact embedded in a groove at one end thereof and bonded to the carbide. The method includes the steps of providing a solid, cylindrical body of cemented carbide having end surfaces joined by a side surface, forming a series of grooves in one end surface, placing compact-forming material in the grooves, exposing the cylindrical body to temperature and pressure conditions suitable to produce an abrasive compact of the material in the grooves and severing the cylindrical body longitudinally from one end surface to the opposite end surface to produce a plurality of drill blanks. The drills are again produced from such blanks by fluting.
Other methods of making micro drill bits are known. Some of these methods, e.g. that described in EP 0 132 652, involve various bonding steps which again adds to the cost. The bonded regions also introduce a potential zone of weakness.
SUMMARY OF THE INVENTION
According to the present invention, a method of making a drill blank, particularly a blank for a micro drill, includes the steps of:
(i) providing a cemented carbide body having a recess formed in a surface thereof,
(ii) placing a layer of ultra-hard abrasive or a mass of ultra-hard abrasive particles on a surface of the recess,
(iii) inserting a cemented carbide piece having the same shape and cross-sectional size as the recess, into the recess,
(iv) subjecting the cemented carbide body to conditions of elevated temperature and pressure suitable to form an abrasive compact of the abrasive particles, when used, and bond such compact or the layer of ultra-hard abrasive to the carbide, and
(v) severing the cemented carbide body through the abrasive compact layer or layer of ultra-hard abrasive to produce one or more drill blanks.
Severing of the cemented carbide body in step (v) takes place in such a manner that the abrasive compact layer, or layer of ultra-hard abrasive, in each drill blank, defines a vein generally located in an end surface of the blank. Each drill blank will generally be elongate in shape and may have a circular, rectangular, square, elliptical or hexagonal or other cross-section.
The cemented carbide body will generally have a surface in which the recess is formed and an opposite surface and severing in step (v) will generally include severing from the one surface to the other surface along first spaced lines, one of which passes through the abrasive layer, and along spaced parallel lines between first spaced lines. The first spaced lines will generally be parallel. Further, the spaced parallel lines will generally be at right angles to the first spaced lines.
The recess may take the form of a cut-out at an edge surface of the cemented carbide body. When the edge surface is a curved surface, the recess may be formed by cutting a segment from that surface.
The cemented carbide body may be disc or elliptical in shape. Other shapes of cemented carbide bodies may also be used in the practice of the invention.
A plurality of recesses may be formed, at least some of which are wholly within the periphery, i.e. the outer peripheral surface, of the cemented carbide body. These recesses may be provided as two spaced banks of recesses. The recesses in one bank are preferably staggered relative to those in the other bank. In this case, severing in step (v) preferably includes severing along a first line passing through the recesses in one bank, along a second line passing through the recesses in the other bank, and along spaced parallel lines between the first and second lines.
At least some of the plurality of recesses may be circular or elongate in plan. When the recesses are elongate in plan, they may be essentially elliptical.
The layer of ultra-hard abrasive may be a layer of diamond produced by chemical vapour deposition. The mass of ultra-hard abrasive particles will generally be a mass of diamond or cubic boron nitride particles, with or without binder, and is suitable to produce an abrasive compact when subjected to elevated temperature and pressure. The conditions of abrasive compact manufacture are well known in the art. Diamond abrasive compacts are also known as PCD, and cubic boron nitride compacts also known as PCBN.
REFERENCES:
patent: 4629373 (1986-12-01), Hall
patent: 4694710 (1987-09-01), Phaal
patent: 4724728 (1988-02-01), Phaal
patent: 4748088 (1988-05-01), Billgren
patent: 4972637 (1990-11-01), Dyer
patent: 5299471 (1994-04-01), Tank et al.
patent: 6029544 (2000-02-01), Katayama
patent: 0 132 652 (1985-02-01), None
patent: 0 206 652 (1986-12-01), None
patent: 0 223 474 (1987-05-01), None
patent: 0251130 (1988-10-01), None
Ashley Boyer
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Rada Rinaldi I.
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