Taper thread tap for pipe

Abstract

To provide a taper thread tap for a pipe, capable of discharging respective chips cut by a chamfer part and a complete taper thread part to the outside without allowing the chips to be entangled with each other.SOLUTION: A taper thread tap 50 for a pipe comprises: a spiral thread part 10 including a chamfer part 1 and a complete taper thread part 2; and grooves 21-23 formed so as to divide the screw part 10. The taper thread tap 50 is configured to have mutually different shapes in an axially perpendicular cross-sectional view of: a sectional shape of a rake face of a cutting edge of the chamfer part 1; and a sectional shape of a rake face of a cutting edge of the complete taper thread part 2.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 tap having a helical thread portion having a lead portion and a full thread taper portion, and a plurality of grooves formed so as to divide the thread portion, in which, when viewed in a cross section perpendicular to the axis of the pipe taper tap, the cross-sectional shape of the rake face of the cutting edge of the lead portion and the cross-sectional shape of the rake face of the cutting edge of the full thread taper portion are different from each other.

[0009] Regarding the cross-sectional shape of each cutting face, the cross-sectional shape of the cutting face of the cutting edge of the cutting edge cutting portion can be a shape that includes a curved portion extending from the tip of the cutting edge toward the base of the cutting edge, and the cross-sectional shape of the cutting face of the cutting edge of the full groove taper portion can be a shape that includes a straight portion extending from the tip of the cutting edge toward the base of the cutting edge. Effect of the Invention

[0010] 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. [Brief description of the drawings]

[0011] [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 taken along line AA of the pipe taper tap 50 shown in FIG. 2. [Figure 4] 3 is a cross-sectional view taken along line BB of the pipe tap 50 shown in FIG. 2. [Diagram 5] 4 is an enlarged view of a cutting edge 1B of the pipe tap 50 shown in FIG. [Figure 6] 5 is an enlarged view of a cutting edge 2B of the pipe tap 50 shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 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.

[0013] 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.

[0014] First, at the tip (edge) 1B of the cutting edge 1A of the chamfer 1 of the pipe taper tap 50, the cross-sectional shape (cross-sectional shape perpendicular to the rotation axis O) of the rake face 1C is formed into a curved shape (hook shape) including a curved portion 1E, and is continuously connected to the cutting edge 1D, as shown in Figures 3 and 5. This is to form thick chips generated by the cutting edge of the chamfer into a small curled shape.

[0015] Next, at the tip (tip) 2B of the cutting edge 2A of the chamfering 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 tapered (rake-shaped) including a straight portion 2E, as shown in Figures 4 and 6. This is because the cutting edge of the full-ridge taper portion from the tip 2B to the bottom 2D acts on the workpiece to perform deep cutting, generating thin chips. As a result, the chips cut at the chamfering portion and the full-ridge taper portion can be discharged outside the pipe taper tap without becoming entangled with each other. [Explanation of symbols]

[0016] 1. Meal section 2 Fully tapered section 1A,2A cutting edge 1B,2B cutting edge 1C,2C scooping face 1D,2D bottom of blade 1E (Cutting face) curved part 2E (Straight section of the rake face) 10 Threaded part 50 Taper pipe tap O Center axis of taper pipe Rotation direction of RT pipe tap

Claims

1. A pipe taper tap comprising a helical thread portion having a chamfer portion and a full thread taper portion, and a plurality of grooves formed so as to divide the thread portion, characterized in that, when viewed in a cross section perpendicular to the axis of the pipe taper tap, the cross-sectional shape of the rake face of the cutting edge of the chamfer portion and the cross-sectional shape of the rake face of the cutting edge of the full thread taper portion are different from each other.

2. 2. The pipe taper tap according to claim 1, wherein a cross-sectional shape of a rake face of the cutting edge of the chamfering portion includes a curved portion extending from the tip of the cutting edge toward the bottom, and a cross-sectional shape of a rake face of the cutting edge of the full crest taper portion includes a straight portion extending from the tip of the cutting edge toward the bottom.

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