JP2007069287A - Highly accurate three-groove drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-groove drill capable of highly accurately performing machining with a longer service life than that by machining by a reamer, without making incorrect the position of a hole made according to a pilot hole in finishing a cast hole of an aluminum alloy cast product even if the pilot hole is eccentric, and without generating chattering during machining. <P>SOLUTION: This three-groove drill is made of high speed tool steel (may be made of cemented carbide) and has a chisel 1, three secondary cutting edges 3 extending outward from the chisel 1, a primary cutting edge 4 extending from each of the secondary cutting edge 3 to a leading edge 2 and three twisted grooves 5 to machine an aluminum alloy or the like. In the drill, a tip angle α is point-ground to 180 to 190° (centrally hollowed). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a three-groove drill for finishing cast holes in aluminum castings.

Conventionally, the punching hole finish of aluminum alloy castings has been processed with a reamer. In drilling a soft material such as an aluminum alloy, a three-groove drill disclosed in Patent Document 1 is known for high-precision drilling.
Japanese Patent Laid-Open No. 5-301108

  However, when a conventional aluminum alloy casting is finished with a reamer, if the pilot hole is eccentric, there is a problem that the hole position is inferior to the pilot hole and chatter occurs during processing. And life span was short. In Patent Document 1, it is disclosed that a high-toughness soft material such as an aluminum alloy can be drilled with high accuracy using a three-blade drill. However, in the thing of patent document 1, the Example which has a tip angle of about 140 degrees seeing on a drawing as an Example is described. As described later, Patent Document 1 has a tip angle of 180 ° or less, which becomes a pilot hole, resulting in a poor hole position, and it is not possible to drill a hole in aluminum alloy casting with high accuracy. In paragraph [0013], in the above-mentioned embodiment, “a secondary cutting edge by thinning is formed in the chisel portion as a drill for drilling. However, a drill for enlarging a hole diameter with respect to a pilot hole may be used. For example, it is not necessary to form a secondary cutting edge, and in that case, the tip surface may be a flat surface instead of a conical surface. " However, since the change of the tip angle and the effect based thereon are not disclosed, “the tip surface may be a flat surface instead of a conical surface” means “secondary cutting. Since it is not necessary to form a blade, it is clear that the central portion does not form a cutting blade and may be a flat surface.

  In view of the above-mentioned problems, the problem of the present invention is that even when the prepared hole is eccentric in the cast hole finishing of the aluminum alloy casting, compared to the processing with a reamer and the conventional 3-blade drill of Patent Document 1, the prepared hole It is an object of the present invention to provide a three-groove drill that does not have a defective hole position, does not generate chatter during machining, has a longer life than machining with a reamer, and can be machined with high precision.

  Therefore, the present invention provides a chisel, three secondary cutting edges formed by thinning extending outward from the chisel, a primary cutting edge extending from each secondary cutting edge to the leading edge, and three A three-groove drill made of cemented carbide or high-speed tool steel for machining aluminum alloys and the like having a torsion groove, with a tip angle of 180 ° to 190 ° (indented). The problems of the present invention described above have been solved.

  In the present invention, the tip angle is set to 180 ° to 190 ° (indented), so in the punching hole processing of aluminum alloy castings, it hits from the outer peripheral side when biting, so even if the pilot hole is eccentric, It can be machined with high accuracy without any defects, the hole position does not become defective, chattering does not occur during machining, and it is possible to drill holes with high guideability and high accuracy with 3 grooves. This provides a three-groove drill that has a longer life than machining at the same time.

  Thinning is not necessary for aluminum alloy castings that are only finished with a punched hole, but the cast hole may be machined from the bottom of the hole, and the length of the secondary cutting edge is preferably 0.1 mm of the drill diameter. When the thinning is performed with the radius of curvature R of the bottom of the thinning groove forming the secondary cutting edge being 0.04 to 0.1 times the diameter of the drill, a hollow hole can be formed. More preferably, the primary cutting edge has a concave portion that follows the secondary cutting edge, and a straight portion that extends substantially linearly to the leading edge at a central angle of 180 ° that follows the concave portion, so that a more accurate hole can be obtained. Can be processed. Furthermore, by having a receding part that recedes in the direction of drill rotation, which is 0.1 to 0.2 times the diameter of the drill following the straight part, further accurate drilling can be performed.

In the present invention, the tip angle is set to 180 ° to 190 °. If the tip angle is 180 ° or less, it becomes a pilot hole and the hole position is poor, and if the tip angle is 190 ° or more, the corner strength decreases. This is because chipping occurs.
In addition, if the length of the secondary cutting edge is less than 0.1 times the diameter of the drill, the effect of the secondary cutting edge is not effective, and if the length of the secondary cutting edge exceeds 0.2 times the diameter of the drill, Since the amount increased and chip accumulation occurred, the length of the secondary cutting edge was limited to 0.1 to 0.2 times the drill diameter. If the radius of curvature R of the bottom of the thinning groove forming the secondary cutting edge is less than 0.04 times the drill diameter, the flow of chips will be poor, resulting in chip accumulation, and if the radius of curvature R exceeds 0.1 times the drill diameter, the chisel edge length Therefore, the radius of curvature R of the bottom of the thinning groove forming the secondary cutting edge is limited to 0.04 to 0.1 times the drill diameter. Furthermore, if the length of the retracted part following the straight part is less than 0.1 times the drill diameter, there will be no effect of increasing the machining accuracy, and if it exceeds 0.2 times the drill diameter, the cutting efficiency will deteriorate. The thickness was limited to 0.1 to 0.2 times the drill diameter.

An example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side view of a drill according to the present invention, and FIG. 2 is an enlarged front view seen from the direction A in FIG.
A three-groove drill according to an embodiment of the present invention is read from a chisel 1, three secondary cutting edges 3 formed by thinning 8 extending outward from the chisel 1, and each secondary cutting edge 3. In high-speed tool steel or cemented carbide three-groove drills for machining aluminum alloys etc. with primary cutting edge 4 extending to edge 2 and three torsion grooves 5, the tip angle α is 180 ° to 190 ° It is sharpened to (indented). 7 is a flank.

  With this three-groove drill with a tip angle α of 180 ° to 190 °, when punching holes in aluminum alloy castings, it hits from the outer periphery when biting, so even if the pilot hole is eccentric, it can follow that. Provides a three-groove drill that can be machined with high accuracy, has no chatter during machining, has a high guideability with three grooves, enables high-precision drilling, and has a longer life than reamer machining. It became a thing.

Thinning may not be required in the case of just finishing a hole in an aluminum alloy casting, but the core hole may be processed by peeling the bottom of the hole. In the three-groove drill according to the embodiment of the present invention, 2 Thinning in which the length of the next cutting edge 3 is 0.1 to 0.2 times the drill diameter d and the radius of curvature R of the thinning groove bottom 6 forming the secondary cutting edge 3 is shortened to 0.04 to 0.1 times the drill diameter d. If 8 is installed, it will be possible to drill holes and perform highly accurate drilling.
Further, the primary cutting edge 4 has a concave portion 41 following the secondary cutting edge 3 and a straight portion 42 extending to the leading edge almost linearly at a position of a central angle of 180 ° following the concave portion 41, thereby achieving higher accuracy. Hole processing is possible. Further, by having a retreating portion 43 that retreats in the direction of drill rotation having a length of 0.1 to 0.2 times the diameter of the drill following the straight portion 42, further highly accurate drilling can be performed.

A cemented carbide three-groove drill having the shape shown in FIGS. 1 and 2 according to the embodiment of the present invention was manufactured. Drill diameter d: 8.5 mm, twist angle β: 30 °, tip angle α: 180 °, with thinning 7 and diamond-like (DLC) coating. The shape of the thinning 7 was a radius of curvature R of the groove bottom 6: 0.5 mm (0.06 times the drill diameter d), secondary cutting edge 3 length: 1.2 mm (0.14 times the drill diameter d). ADC12 was processed using this cemented carbide 3 groove drill. The machining conditions were cutting speed: 200 m / min (7500 m ⁻¹ ), feed amount: 0.51 mm / rev (3820 mm / min). FIG. 3 shows a machining schematic diagram of the holes machined in the experiment in Example 1. A hole depth f40 mm was machined against a drilled hole diameter a: φ8.5 mm, a pilot hole diameter b: φ5.5 mm, a pilot hole eccentricity c: 1 mm, and a pilot hole depth e: 30 mm. As comparative products, a three-groove drill with a tip angle of 150 ° and a two-blade drill with a tip angle of 140 ° were processed under the same conditions.

  The results are shown in FIG. FIG. 4 shows the positional deviation amount and the hole bending amount of the finishing hole. According to FIG. 4, the misalignment amount was 0.2 mm and 0.6 mm for each of the three-groove drills with a tip angle of 150 ° and 140 ° according to FIG. Results were obtained.

  Furthermore, drilling with a tip angle of 180 °, a thinning shape with a radius of curvature R: 0.2mm (0.02 times the drill diameter d) and a second cutting edge length of 3mm (0.35 times the drill diameter d) is also possible. Went. In this drill, chips were clogged in the thinning part at 10 holes, but in the drill of the present invention, clogging of the thinning part was not observed even after 100 holes were continuously processed.

  In this embodiment, the coating is a diamond-like (DLC) coating, but it is needless to say that the coating may be a coating suitable for processing an aluminum alloy such as diamond.

The side view of the drill of this invention is shown. The details of the thinning are shown in the enlarged front view from the direction A in FIG. The process schematic of the hole processed by experiment in Example 1 is shown. The table | surface which shows the experimental result of Example 1. FIG.

Explanation of symbols

1: chisel, 2: leading edge, 3: secondary cutting edge, 4: primary cutting edge,
5: Twist groove, 6: Thinning groove bottom, 8: Thinning, 41: Concave part of primary cutting edge,
42: Linear part of the primary cutting edge, 43: Retraction part of the primary cutting edge, α: Tip angle, d: Drill diameter

Claims (4)

  Aluminum having a chisel, three secondary cutting edges formed outwardly from the chisel, a primary cutting edge extending from each secondary cutting edge to the leading edge, and three twist grooves A three-groove drill made of cemented carbide or high-speed tool steel for machining alloys, etc., having a tip angle of 180 ° to 190 °.   The length of the secondary cutting edge is 0.1 to 0.2 times the diameter of the drill, and the curvature radius R of the bottom of the thinning groove forming the secondary cutting edge is set to 0.04 to 0.1 times the drill diameter. The three-groove drill according to claim 1.   The said primary cutting edge has a recessed part following the said secondary cutting edge, and a linear part extended to the leading edge substantially linearly in the position for every central angle 180 degrees following the said recessed part, or characterized by the above-mentioned. The three-groove drill according to claim 2.   4. The three-slot drill according to claim 3, further comprising a retreating portion that retreats in the direction of drill rotation having a length of 0.1 to 0.2 times the diameter of the drill following the straight portion.

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