Taper tap for pipe

Abstract

To provide a taper tap for pipes capable of discharging each chip to the outside and suppressing gouge of a processed surface without entangling respective chips machined with one another by a chamfered part and a fully tapered part.SOLUTION: A taper tap for a pipe 50 including a spiral screw part 10 having a chamfered part 1 and a fully tapered part 2 and three strips of grooves 21, 22, 23 for dividing the screw part 10 to remove screw threads of each land in the screw part 10 by one thread at a time includes a curved portion extending from the tip of a cutting edge toward the bottom of the cutting edge in a cross-sectional shape of the rake face of the cutting edge of the chamfered part 1 in a cross-sectional view perpendicular to the axis of the taper tap for a pipe 50, includes a linear portion extending from the tip of cutting edge toward the bottom of the cutting edge in the cross-sectional shape of the rake face of the cutting edge of the fully tapered part 2, and executes rounding processing (R chamfering) to the tip of the cutting edge of the chamfered part.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a taper tap for pipes that forms a screw hole in a workpiece by cutting. [Background technology]

[0002] Until now, chips generated during cutting of pipe tapers have taken on various forms, and the processing performance of the pipe tapers has been greatly affected by the form. For example, in pipe tapers for blind holes, coil-shaped chips have been preferentially discharged by setting the helix angle of the flute to 30° or more.

[0003] Also, by providing a separate groove (sub-groove) in addition to the original groove at the tip of the pipe tap, the chips can be broken up.Furthermore, as disclosed in Patent Documents 1 to 3, by setting the twist angle of the groove to 0°, that is, to be approximately parallel to the rotation axis of the pipe tap, the chips can be broken up and discharged. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5301452 [Patent Document 2] Patent No. 5866271 [Patent Document 3] Patent No. 5816368 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the cutting edge (cross-sectional shape of the cutting edge) of the chamfer of a pipe taper tap is hook-shaped, the chips of the workpiece become curled, and at the same time, the rake angle of the full-ridge taper portion becomes weak, inducing chipping of the machined surface. In addition, there is a problem that the increased cutting resistance promotes tool wear.

[0006] On the other hand, when the cutting edge of a taper pipe tap (the cross-sectional shape of the cutting edge) is rake-shaped, the rake angle is constant from the tip to the base of the blade, so the cutting resistance is small and damage to the machined surface can be suppressed. However, when the workpiece is mainly stainless steel or general-purpose steel, the curling property of the generated chips cannot be exhibited, and the curl diameter tends to become large.

[0007] Therefore, an object of the present invention is to provide a taper tap for pipes that can discharge the chips machined at the chamfer portion and the full crest taper portion to the outside without them becoming entangled, thereby suppressing damage to the machined surface. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the pipe taper tap of the present invention is a pipe taper tap having a helical thread portion having a lead portion and a full thread taper portion, and three grooves formed to divide the thread portion, in which the threads of each land in the thread portion are removed every other thread, and in a cross-sectional view perpendicular to the axis of the pipe taper tap, part of the cross-sectional shape of the rake face of the cutting edge of the lead portion has a curved portion extending from the tip (of the cutting edge) toward the base of the cutting edge, and part of the cross-sectional shape of the rake face of the cutting edge of the full thread taper portion has a straight portion extending from the tip (of the cutting edge) toward the base of the cutting edge, and the tip of the cutting edge of the lead portion is rounded (R chamfered).

[0009] Furthermore, the cutting edge of a part of the cutting edge in the full crest taper portion is also rounded, and the radius of curvature of the rounded cutting edge of the chamfer portion is made larger than the radius of curvature of the rounded cutting edge of the part of the cutting edge in the full crest taper portion. In this case, the radius of curvature of the rounded cutting edge of the chamfer portion may be 20 μm or more, and the radius of curvature of the rounded cutting edge of the part of the cutting edge in the full crest taper portion may be 10 μm or more.

[0010] The helix angle of the pipe tap flute may be in the range of 30° to 40°, and the rake angle of the cutting edge of the chamfer may be in the range of 10° to 20°. The helix angle of the flute may be 38°, and the rake angle of the cutting edge of the chamfer may be 15°. Effect of the Invention

[0011] In the pipe taper tap of the present invention, the cutting edge of the chamfer portion cuts the workpiece (chips) and discharges them in a curled state due to the action of the curved rake face. At the same time, the cutting edge of the full crest portion is a straight cutting edge, so the workpiece can be cut with a constant rake angle from the tip to the base of the cutting edge. This has the effect of enabling the chips cut by the chamfer portion and the full crest portion to be discharged outside the pipe taper tap without becoming entangled with each other.

[0012] Additionally, by rounding the edges of the cutting edges at the chamfering portion and some of the cutting edges at the full thread taper portion, wear on the cutting edges at the chamfering portion is reduced, the sealing performance of the tapered thread portion of the workpiece is ensured, and cracks on the machined surface are suppressed. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a front view of a pipe taper tap 50 according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a right side view of a pipe taper tap 50 according to an embodiment of the present invention. [Diagram 3] 3 is a cross-sectional view of the pipe taper tap 50 shown in FIG. 2 taken along line AA. [Figure 4] 3 is a cross-sectional view of the pipe taper tap 50 shown in FIG. 2 taken along line BB. [Diagram 5] 4 is a schematic enlarged view of a cutting edge 1B of the pipe tap 50 shown in FIG. [Figure 6] 5 is a schematic enlarged view of a cutting edge 2B of the pipe tap 50 shown in FIG. 4. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] An embodiment of the pipe taper tap of the present invention will be described with reference to the drawings. FIG. 1 shows a front view of a pipe taper tap 50 according to an embodiment of the present invention, and FIG. 2 shows a right side view thereof. As shown in FIG. 1 and FIG. 2, the pipe taper tap 50 of the present invention is formed of a thread portion 10 for threading a workpiece and three grooves 21, 22, and 23 (in order from the rotation direction RT of the pipe taper tap 50) formed to divide the thread portion 10. Chips of the workpiece cut by the thread portion 10 are discharged to the outside of the pipe taper tap 50 through the grooves 21, 22, and 23. The thread portion 10 is formed of a chamfer portion 1 and a full thread taper portion 2 as shown in FIG. 2.

[0015] A cross-sectional view of the pipe taper tap 50 shown in Fig. 2 taken along line AA (cross-sectional view perpendicular to the rotation axis O) is shown in Fig. 3, and a cross-sectional view of the pipe taper tap 50 taken along line BB (cross-sectional view perpendicular to the rotation axis O) is shown in Fig. 4. Fig. 5 shows a partially enlarged view of the cutting edge tip (edge) 1B of the pipe taper tap 50 shown in Fig. 3, and Fig. 6 shows a partially enlarged view of the cutting edge tip (edge) 2B of the pipe taper tap 50 shown in Fig. 4.

[0016] At the tip (edge) 1B of the cutting edge 1A of the chamfer 1 of the pipe taper tap 50, as shown in Figures 3 and 5, the cross-sectional shape of the rake face 1C (cross-sectional shape perpendicular to the rotation axis O) is formed into a curved shape (hook shape) including a curved portion 1E, and is continuously connected to the cutting edge 1D. This is to form thick chips generated by the cutting edge of the chamfer during cutting of the thread into a small curl shape. In addition, the edge 1B of the cutting edge 1A of the chamfer 1 is rounded (radius of curvature: about 20 μm) as shown in Figure 5.

[0017] Next, at the tip (edge) 2B of the cutting edge 2A of the full thread taper portion 2 of the pipe taper tap 50, the cross-sectional shape (cross-sectional shape perpendicular to the rotation axis O) of the rake face 2C is a tapered shape (rake shape) including a straight portion 2E, as shown in Figures 4 and 6. This is because when machining the threads, the cutting edge of the full thread taper portion is made to act on the workpiece from the tip to the bottom, thereby cutting deeply and generating thin chips.

[0018] In other words, by forming each cutting edge in the chamfer and full crest taper as described above, the chips produced by the cutting process in the chamfer and full crest taper do not become entangled and can be discharged to the outside of the pipe taper tap. In addition, the cutting edge 2B of the cutting edge 2A of the full crest taper 2 is rounded (radius of curvature: about 10 μm) as shown in FIG.

[0019] In this case, the radius of curvature of the cutting edge of the chamfer is made larger than the radius of curvature of the cutting edge of the full crest tapered portion. This is because rounding the cutting edge of the chamfer improves chipping resistance and wear resistance against the workpiece, while the cutting edge of the full crest tapered portion maintains its cutting performance (sharpness) against the workpiece, thereby suppressing the occurrence of chipping on the machined surface of the workpiece cut by the cutting edge of the chamfer. [Explanation of symbols]

[0020] 1. Meal section 1A,2A cutting edge 1B,2B cutting edge 1C,2C scooping face 1D,2D bottom of blade 1E (Cutting face) curved part 2 Fully tapered section 2E (Straight section of the rake face) 10 Threaded part 21, 22, 23 Groove (Twisted Groove) 50 Taper pipe tap O Center axis of taper pipe Rotation direction of RT pipe tap

Claims

1. a cutting edge of the full thread taper portion having a straight portion extending from the tip of the cutting edge toward the bottom of the cutting edge, and a cross-sectional shape of the cutting edge of the full thread taper portion having a rounded edge, the cutting edge of the cutting edge being rounded, and a helical thread having a chamfer portion and a full thread tapered portion, the threads of which are removed every other thread of each land in the threaded portion, the cross-sectional shape of the cutting edge of the chamfer portion having a curved portion extending from the tip of the cutting edge toward the bottom of the cutting edge, and the cross-sectional shape of the cutting edge of the full thread tapered portion having a straight portion extending from the tip of the cutting edge toward the bottom of the cutting edge, and the cutting edge of the cutting edge of the chamfer portion being rounded.

2. 2. The pipe taper tap according to claim 1, further characterized in that the cutting edges of some of the cutting edges in the full crest taper portion are also rounded, and the radius of curvature of the rounded cutting edges of the cutting edges in the chamfer portion is larger than the radius of curvature of the rounded cutting edges of some of the cutting edges in the full crest taper portion.

3. 3. The pipe taper tap according to claim 2, wherein the radius of curvature of the rounded cutting edge of the chamfer portion is 20 μm or more, and the radius of curvature of the rounded cutting edge of a portion of the full crest taper portion is 10 μm or more.

4. 4. The pipe taper tap according to claim 3, wherein the helix angle of the flute is in the range of 30° to 40°, and the rake angle of the cutting edge of the chamfer portion is in the range of 10° to 20°.

5. 5. The pipe taper according to claim 4, wherein the helix angle of the flute is 38 degrees, and the rake angle of the cutting edge of the chamfer portion is 15 degrees.

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