Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B51/00—Tools for drilling machines
  • B23B51/02—Twist drills
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B2251/00—Details of tools for drilling machines
  • B23B2251/18—Configuration of the drill point
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B2251/00—Details of tools for drilling machines
  • B23B2251/24—Overall form of drilling tools
  • B23B2251/241—Cross sections of the diameter of the drill
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B2251/00—Details of tools for drilling machines
  • B23B2251/40—Flutes, i.e. chip conveying grooves
  • B23B2251/406—Flutes, i.e. chip conveying grooves of special form not otherwise provided for
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B2270/00—Details of turning, boring or drilling machines, processes or tools not otherwise provided for
  • B23B2270/30—Chip guiding or removal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B51/00—Tools for drilling machines
  • B23B51/011—Micro drills

Definitions

• the present invention relates to twist drills and more particularly to so-called micro twist drills which are adapted for drilling holes for a diameter of 0.125 inches and usually le than 0.050 inches.
• Micro drills range in sizes from approximately 0.125 inches down to about 0.002 inches in diameter and are employed for many precision purposes. They are used to provide precision holes in plastic, metal and the like, in the manufacture of such products as printed circuit boards, carburetors, watches and the like. Such drills often have a relatively short life and th other problems which they present relate to the removal of chips and the precision of the hole which is formed by the drill Because of the small sizes of the drills the chips generated are extremely small, but at the same time, there is not a sufficient large passageway in the flutes to carry away the chips. Also, w normal drill constructions the chips are worked against the side walls of the hole being drilled by the rotation of the drill and tend to cause galling on the sides of the holes.
• a micro twist drill having a rigid cylindrical body with a drill point t one end and having two oppositely disposed flutes helically extending along said body from said drill point to define a pair of oppositely disposed helically extending wings.
• Each wing has a leading surface in relation to the direction of rotation of the drill and the leading surface is undercut to provide a peripheral, positive rake, cutting edge which makes an angle of from about 5° to about 30° to a radius of said cylindrical body which extends to said cutting edge.
• the wings are symetrically disposed relative to one another to provide a drill body with a traverse cross section of a generally S-shape wherein the leadin surface of each wing is provided with a curved channel trailing (relative to the direction of rotation of the drill) a line bet ⁇ ween the cutting edges of said two wings and wherein the trailin surfaces of each of said wings defines a curve which substantial continuously recedes from the path of the cutting edge to the point at which it meets the leading surface of the other wing.
• FIGURE 1 is a fragmentary side view of a drill embodyin the construction which is ordinarily employed in the prior art;
• FIGURE 2 is an end view of the drill shown in FIGURE 1;
• FIGURE 3 is a side view of a drill embodying various features of the invention.
• FIGURE 4 is an end view of a drill shown in FIGURE 3;
• FIGURE 4A is a fragmentary enlargement of a portion of
• FIGURE 4 is a side view of another embodiment of a dril embodying various features of the invention.
• FIGURE 6 is an end view of the drill shown in FIGURE 5.
• FIGURES 1 and 2 illustrate a drill 11 having the usual prior art configuration.
• the drill 11 is made from a length of cylindrical stock which is provided wit a pair of opposed helical flutes 13 which provides a drill body or web 15 having a pair of opposed wings 17.
• the wing 17 includes a face 19 which is parallel to a radius 21 of the drill and is positioned ahead of the radius 21 based upon the direction of rotation of the drill.
• the cutting action of the drill is accomplished by the drill tip 22 and by a so-called chisel edge 23 at the peripheral edge of the face 19 insofar as concerns the outer diameter of the hole being drilled.
• Rear- wardly (with reference to the direction of rotation of the drill from the chisel edge 23, the wing 17 is provided with a land 25 which provides a circumferential arcuate area which determines the diameter of the drill.
• the land 25 follows the helical path of each of the flutes 13 up to the shank of the drill.
• the remainder or heel 29 of the wing 17 follo the curvature of the path 30 of the chisel edge 23 but is inwardl spaced therefrom as illustrated.
• the distance from the chisel edge 23 to the end 31 of the heel 29 is normally of the order of about 90° of arc or more.
• the wing is defined by a concave surface 33, which merges in to the face 19 of the opposite wing.
• the tip 22 of the drill is sharpened in the usual manner with a tip angle of from about 90° to 120°, this angle varying in the manner known to the art depending upon the material being drilled.
• the usual drill is provided with a back taper so that the diameter across the lands 25 at the tip of the drill is larger than the diameter across the lands adjacen the shank.
• This is known as "back taper” and is employed to reduce the friction between the lands 25 and the wings 17 against the sides of the hole at points remote from the tip 22.
• the face 19 of the wing 17 forms an acute angle with the wall of the hole indicated by the dotted line 30 which is the path of the chisel edge 23 in FIGURE 2, so that as the drill turns and the chips are forced out of the hole being drilled, they are constantly wedged between the wall of the hole and the land 25 causing galling of the wall.
• galling is extremely undesirable because it can destroy tolerances.
• the galling problem is aggravated at positions remote from the tip because of the back taper.
• FIGURES 3 and 6 illustrate various features of the present invention.
• our improved micro twist drill comprises a rigid cylindrical body having two oppositely disposed
• each of the wings has a lea surface in relation to the direction of rotation of the drill, the leading surface being undercut to provide a peripheral, positive rake cutting edge which makes an angle of from about 5° to about 30° to a radius of the cylindrical body which extends t the cutting edge.
• the wings are symmetrically disposed relative to one another to provide a drill body or web which is in trans- verse cross section of generally "S" shape.
• each wing is provided with a channel, a substantial portion o which trails (relative to the direction of rotation of the drill a line between the cutting edges of the two wings, so as to pro ⁇ vide a channel inwardly of the cutting edge along which chips wi be transported out of the hole being drilled.
• the trailing surf of each of the wings is defined by a surface which substantially continuously recedes from the path of the cutting edge to the point at which it meets the leading surface of the other wing. This construction provides passageways for chips in the flutes which are of large cross section and which have substantially no corners or grooves in which chips or other debris can be lodged.
• the micro drill includes a circumferential land between the cutting edge of each wing and the point where the trailing surface of the wing recedes from the path of the cutting edge.
• the land on each wing is of a width which subtends an arc of less than about 12°.
• FIGURES 3 and 4 which illustrate one embodiment of a drill embodying features of the invention
• the drill is fabricated from a rigid cylindrical body 37 from suitable materials known to the drill art.
• the drill material will be dependent upon the material being drilled and the life required for the drill, all as known in the art.
• two oppositely disposed flutes 39 are provided which helically extend from the drill point 40 along the body 37 towards shank 41 of the drill.
• the flutes 39 define a pair of oppositely disposed helically extending wings 43.
• the helix angle is consta in the illustrated drill. However, depending upon the action requred in removing chips it can be varied along the length of th drill to accelerate the removal of chips after they leave the are adjacent the tip of the drill by decreasing the helix angle in th area remote from the tip 40.
• Each of the wings 43 has a leading surface 45 in relati to the direction of rotation of the drill, the surface 45 being undercut adjacent its periphery to provide a positive rake cuttin edge 47. It has been found that a tangent to the face 45 at the cutting edge should make an angle of from about 5° to about 30° t a radius 49 of the cylindrical body which extends to the cutting edge 47, angle "A" in FIGURE 4. As illustrated, the wings 43 are symmetrically disposed relative to one another to provide a drill web which is generally of "S" shape.
• each wing In order to cause the chips to be directed inward ⁇ ly away from the cutting edge the leading surface of each wing is forme ⁇ in a concave shape to provide a channel or trough 51, a substantial portion of which trails the radius 49 which extends to the cutting edge 47.
• the chips formed by the drilling operation will be moved inwardly by the positive rake cutting edge away from the sides of the hole being drilled.
• the rotation of the drill causes the chips to be moved out of the drill hole in the flutes 39.
• Each of the wings 43 is provided with a trailing surface 53 which begins at the periphery of the drill body and substantially continuously recedes from the periphery of the drill body.
• both the leading surfaces 45 and the trailing surfaces 53 are smooth, concave and convex curves, respectively, with a smooth transition therebetween.
• the drill point 40 may be ground on the end of the drill remote from the shank in the usual manner. As in conventional drills, the point will be ground to provide a tip angle at the point of from approximately 90° to approximately 120°. The exact angle depends upon the material being drilled, all as know in the art.
• the drill is rotated in the material to be drilled and the chips generated by the tip will move inwardly of the periphery of the hole along the channels provide in the leading edge of each of the wings.
• the cutting edge and its associated land move along the walls of the hole being drill and have the function of scouring the walls and collecting any chips which might adhere to the walls and move them into the channel 51. Any chips which are not collected by the cutting • edge and pass between the land and the walls of the hole being drilled have little tendency to become lodged on the smooth conv surface 53 of the trailing edge of the wing but instead are collected and transported out of the hole by the next succeeding wing.
• the cutting edge makes an angle " with the radius 49 in the range of from about 5° to about 30°. Preferably, the angle is maintained between about 5° and 15°, and most preferably about 10°.
• Drills as described above, with an appropriate point have been found to drill materials of all types with a minimi ⁇ zation of galling and a minimization of wobbling along the drill length as a result of the effective removal of chips.
• FIGURES 5 and 6 illustrate a drill of the type illust- rated in FIGURES 3 and 4, the drill being provided with a so- called split point. This enhances the speed of drilling and aids in drilling an accurate hole.
• Split points are known in the art and are formed by grinding away a pair of triangular areas as illustrated at 57 and 59 in FIGURES 5 and 6.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Drilling Tools (AREA)

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Publications (1)

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ID=22168182

Family Applications (1)

Country Status (2)

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• 1982
  • 1982-09-07 WO PCT/US1982/001223 patent/WO1984000910A1/en unknown
  • 1982-09-07 EP EP82902964A patent/EP0118431A1/de not_active Withdrawn

Non-Patent Citations (1)

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