Interlap tap

Abstract

To provide an interlap tap in which seal performance of a taper screw part of a material to be ground is secured, while reducing abrasion of a cutting blade of a biting part, so that burr is suppressed from occurring on a processed surface.SOLUTION: In an interlap tap 50 which comprises a spiral-shape screw part 10 having a biting portion 1 and a complete thread taper portion 2 and three grooves 21-23 formed to divide the scree part 10, where every other screw threads of each land are removed, at least a blade edge of a cutting blade of the biting part 1 is subjected to rounding processing. Further blade edges of some cutting blades at the complete thread taper part 2 may be subjected to rounding processing.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an interrupt tap for forming a screw hole in a workpiece by cutting. [Background technology]

[0002] Conventionally, taper pipe taps have a cutting edge with a full-thread taper section that cuts into the workpiece of approximately 4 to 11 μm, meaning that the cutting process proceeds in a state where the cutting edge rubs against the workpiece, making the machined surface prone to chipping.

[0003] To address the problem of chipping on the machined surface, rounding only the cutting edge (R chamfering) of the entire cutting edge suppresses micro-chipping of the cutting edge and chipping on the machined surface of the workpiece. There is also an "interrupt tap" which is a tap formed by partially thinning out the cutting edges of the full thread taper. Compared to general pipe tapers, this has fewer cutting edges in the full thread taper, so the amount of cutting into the workpiece during cutting per blade is large, making it less likely to cause chipping on the machined surface (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5816368 [Patent Document 2] Patent No. 5756562 Summary of the Invention [Problem to be solved by the invention]

[0005] However, while rounding the edge of the cutting edge in the chamfering section can prevent chipping of the cutting edge and has a certain degree of effect in preventing chipping, there is a problem in that if the edge of the entire cutting edge in the full tapered section is also rounded, the effect of preventing chipping decreases if the amount of rounding of the cutting edge becomes greater than the amount of cut (depth of cut) during cutting.

[0006] In addition, because interrupt taps have a larger cutting depth per cutting edge in the workpiece, they have fewer cutting edges than general pipe taps, which means that the step caused by the stop marks becomes larger and the sealing ability of the tapered thread portion of the workpiece is easily compromised.

[0007] Therefore, an object of the present invention is to provide an interrupt tap that reduces wear on the cutting edge of the chamfering portion while ensuring the sealing performance of the tapered thread portion of the workpiece, thereby suppressing damage to the machined surface. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides an interrupt tap that has a helical threaded portion having a chamfer portion and a full thread tapered portion, and three grooves (helical grooves) formed to divide the threaded portion, and in which the threads of each land are removed every other thread, the cutting edge of the chamfer portion is rounded. At this time, the cutting edges of some of the cutting edges in the full thread tapered portion may also be rounded.

[0009] In addition, in a cross section parallel to the longitudinal direction (axial direction) of the interrupt tap, the radius of curvature of the cutting edge of the chamfering portion can be made larger than the radius of curvature of the cutting edge of some of the cutting edges in the full crest tapered portion. For example, the radius of curvature of the cutting edge of the chamfering portion can be made 20 μm or more, and the radius of curvature of the cutting edge of some of the cutting edges in the full crest tapered portion can be made 10 μm or more. Effect of the Invention

[0010] The interrupt tap of the present invention reduces wear on the cutting edge of the chamfering portion, ensures sealing performance of the tapered thread portion of the workpiece, and suppresses damage to the machined surface. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a front view of an interrupt tap 50 according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a right side view of an interrupt tap 50 according to an embodiment of the present invention. [Diagram 3] 3 is a cross-sectional view of the interrupt tap 50 shown in FIG. 2 taken along line AA. [Figure 4] 3 is a cross-sectional view taken along line BB of the interrupt tap 50 shown in FIG. 2. [Diagram 5] 3 is a cross-sectional view taken along line CC of the interrupt tap 50 shown in FIG. 2. [Figure 6] 4 is a schematic enlarged view of a tip of a cutting edge 11 of the interrupt tap 50 shown in FIG. 3. [Figure 7] 5 is a schematic enlarged view of a tip of a cutting edge 11 of the interrupt tap 50 shown in FIG. 4. [Figure 8] 6 is a schematic enlarged view of a tip of a cutting edge 11 of the interrupt tap 50 shown in FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The form of the tap of the present invention will be described with reference to the drawings. FIG. 1 shows a front view of a tap 50 according to an embodiment of the present invention, and FIG. 2 shows a right side view. As shown in FIG. 1, the interrupt tap 50 is formed of a thread portion 10 for threading a workpiece and three grooves (helical grooves) 21, 22, and 23 formed to divide the thread portion 10. Chips of the workpiece cut by the thread portion 10 are discharged to the outside of the interrupt tap 50 through the three grooves 21-23. As shown in FIG. 1, the thread portion 10 is formed of a chamfer portion 1 and a full thread tapered portion 2, and each cutting edge formed on the front side of each of the grooves 21-23 in the rotation direction RT is formed continuously as a single cutting edge from the chamfer portion 1 to the full thread tapered portion 2.

[0013] A cross-sectional view of the interrupt tap 50 shown in Fig. 2 taken along line AA (cross-sectional view perpendicular to the rotation axis O) is shown in Fig. 3, a cross-sectional view taken along line BB (cross-sectional view perpendicular to the rotation axis O) is shown in Fig. 4, and a cross-sectional view taken along line CC (cross-sectional view perpendicular to the rotation axis O) is shown in Fig. 5. A schematic enlarged view of the tip of the cutting edge 11 shown in Fig. 3 is shown in Fig. 6, a schematic enlarged view of the tip of the cutting edge 11 shown in Fig. 4 is shown in Fig. 7, and a schematic enlarged view of the tip of the cutting edge 11 shown in Fig. 5 is shown in Fig. 8.

[0014] The tip of the cutting edge 11 of the chamfer 1 is rounded (radius of curvature: about 20 μm) as shown in Fig. 6. The tip of the cutting edge 11 of the full crest tapered portion 2 is rounded (radius of curvature: about 10 μm) on the cutting edge closer to the chamfer as shown in Fig. 7. In this case, the radius of curvature of the rounded tip of the cutting edge 11 of the chamfer is made larger than the radius of curvature of the rounded tip of the cutting edge 11 of the full crest tapered portion. In contrast, the tip of the cutting edge 11 of the full crest tapered portion closer to the shank side of the interrupt tap 50 is not rounded as shown in Fig. 8.

[0015] This is because rounding the tip of the cutting edge in the chamfering portion serves to improve the chipping resistance and wear resistance of the workpiece, while the cutting edge in the full tapered portion maintains its cutting performance (sharpness on the workpiece) on the workpiece, thereby suppressing the occurrence of chipping on the machined surface of the workpiece cut by the cutting edge in the chamfering portion. [Explanation of symbols]

[0016] 1. Meal section 2 Fully tapered section 10 Threaded part 11 Cutting edge 21, 22, 23 Groove (Twisted Groove) 50 Interrupt Tap O Central axis of interrupt tap RT Interrupt tap rotation direction

Claims

1. An interrupt tap comprising a helical thread portion having a chamfer portion and a full thread tapered portion, and three grooves formed so as to divide the thread portion, and in which the threads of each land are removed every other thread, the cutting edge of the chamfer portion being rounded.

2. 2. The interrupt tap according to claim 1, further comprising a rounded cutting edge at a portion of the cutting edge of the full crest tapered portion.

3. 4. The interrupt tap according to claim 3, characterized in that, in a longitudinal cross-sectional view of the interrupt tap, a radius of curvature of the rounded cutting edge of the chamfer portion is larger than a radius of curvature of the rounded cutting edge of a portion of the cutting edge in the full crest tapered portion.

4. 4. The interrupt tap according to claim 3, 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 cutting edge in the full crest taper portion is 10 μm or more.

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