JP2011161579A - Cutting tap - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cutting tap which reduces the surface roughness of a flank of a female screw formed on a workpiece. <P>SOLUTION: The flanks of a female screw formed by the cutting edge of a leading part 21 are positioned on the axis O side of flanks on both sides of a female screw to be cut on a workpiece. Since the crests of the leading part 21 and a complete thread part 22 are set to have the same lead, the whole parts of one and the other of the flanks of the female screw cut by the cutting edge of the leading part 21 are cut by the cutting edge of the complete thread part 22 when shifting from the leading part 21 to the complete thread part 22. Thus, since one of the flank of the thread of the female screw cut by the cutting edge of a first leading part 23 is cut by the cutting edge of the complete thread part 22, the surface roughness of one of the flank of the female screw is reduced. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cutting tap, and more particularly to a cutting tap that can reduce the surface roughness of a flank of a female screw formed on a work.

  As a cutting tool used when forming a female screw in a prepared hole provided in a work, a cutting tap having a bite portion and a complete thread portion is generally known.

  Now, a conventional cutting tap 500 will be described with reference to FIG. FIG. 4A is a schematic diagram schematically showing the screw portion 520 in the conventional cutting tap 500, and FIG. 4B is a diagram showing the screw threads 521a to 521d of the biting portion 521 and the complete thread portion 522. 4C is a schematic diagram schematically showing the trajectory of 522a, and FIG. 4C schematically shows the cutting portions 521a1 to 521d1 and 522a1 by the thread portions 521a to 521d and 522a of the bite portion 521 and the complete thread portion 522. FIG.

  As shown in FIG. 4A, the cutting tap 500 includes a threaded portion 520 having a biting portion 521 and a complete peak portion 522, a groove (not shown) from which chips are discharged, and along the groove. And a cutting edge (not shown) formed on the screw portion 520. The chamfered portion 521 is formed with thread leads 521a to 521d of the same lead as the complete thread portion 522, and then is chamfered to the top of the screw threads 521a to 521d, and toward the axial center toward the tip side. It is formed to be inclined downward. Thereby, since the cutting torque of the front end side (right side of Fig.4 (a)) of the cutting tap 500 can be reduced, the biting of the cutting tap 500 with respect to a workpiece can be improved.

  As shown in FIG. 4B, in the internal thread processing by the cutting tap 500, the cutting site cut by the cutting edges of the thread 521a to 521d, 522a of the bite portion 521 and the complete thread portion 522 by lead feed. By accumulating 521a1 to 521d1, 522a, a female thread is formed on the work piece.

Japanese Examined Patent Publication No. 37-13848 (Fig. 1)

  However, when forming a female thread on the work with the conventional cutting tap 500, an error may occur in the lead feed of the cutting tap 500. For example, when the cutting tap 500 is a spiral tap having a twist groove, the chips are discharged to the rear side (the left side in FIG. 4B) with respect to the traveling direction of the cutting tap 500 by the chip discharging action of the grooves. . At this time, the cutting tap 500 is pushed out to the advancing direction side (right side of FIG. 4B) by the reaction force of chip discharge. Therefore, as shown in FIG. 4 (c), when the internal thread machining is performed by the cutting tap 500, the feed amount of the cutting tap 500 advances more than the regular feed amount, and the thread 521a to 521d of the bite portion and the complete thread Cutting sites 521a1 to 521d1 and 522a1 cut by the cutting edge of the thread 522a of the crest 522 are displaced toward the traveling direction side of the cutting tap 500. As a result, one flank 551 of the female thread formed on the work is stepped, and irregularities are formed.

  Further, when a lead error occurs in the biting portion 521 when the cutting tap 500 is manufactured, the screw threads 521a to 521d of the biting portion 521 and the screw threads 522a of the complete screw portion 522 are equal to the lead error size. The cutting parts 521a1 to 521d1 and 522a1 cut by the cutting blades are similarly displaced.

  As described above, conventionally, there is a problem that one flank 551 or the other flank 552 of the female thread 550 formed on the work is stepped to form irregularities and increase the surface roughness. was there.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a cutting tap that can reduce the surface roughness of the flank of the female thread formed on the work.

Means for Solving the Problems and Effects of the Invention

  According to the cutting tap of claim 1, since the effective diameter of each biting portion is set to be smaller than the complete peak portion, the flank of the screw is formed on the work piece because it is formed by the cutting edge of the biting portion. It is located on the axial center side with respect to the flank on both sides of the female screw to be cut. In addition, the root of the root that connects the chamfered part and the complete crest is set larger than the lead of the female thread, so that the crest of the thread of the threaded part is all set to the same lead. When moving to the crest, it is cut by the cutting edge of the biting portion, so that one whole flank of the screw and the whole other flank can be cut by the cutting edge of the complete crest. Therefore, when there is a pitch error in the biting part of the cutting tap, or when the feed amount of the cutting tap advances or lags more than the normal feed amount, the work piece is cut by the cutting edge of the biting part. Therefore, even if the surface roughness of one flank of the screw or the other flank increases, the one flank and the other flank can be finished flat. Therefore, there is an effect that the surface roughness of the flank on both sides of the female screw can be reduced.

  According to the cutting tap of claim 2, the biting portion has a biting triangle because the pointed triangle of the screw thread is formed in the same shape as the complete peak portion and is located on the axial center side with respect to the complete peak portion. Since the thread flank is formed by the cutting edge of the part, the flank of the thread is positioned closer to the axial center than the flank on both sides of the female thread to be cut into the work. Further, since the root of the valley bottom connecting the chamfered portion and the complete crest is set larger than the lead of the female screw, the crests of the threads of the threaded portion are all set to the same lead. Similar to the cutting tap, there is an effect that the surface roughness of the flank on both sides of the female screw can be reduced.

  According to the cutting tap of claim 3, since the effective diameter of the biting part is set smaller than the complete peak part, the flank of the screw is formed on the work piece because it is formed by the cutting edge of the biting part. It is located on the axial center side with respect to the flank on both sides of the female screw to be cut. In addition, after the thread portion forms a screw thread in which the valley bottoms are all set to the same lead, among the thread threads that connect the bite part and the complete thread part, at least the bite part shifts to the complete thread part. By grinding the follower flank formed on the thread of the immediately preceding cutting edge, the lead of the follower flank is set larger than the lead of the female thread, so when moving from the bite to the complete thread, Since it is cut by the cutting edge of the chamfered portion, the entire one flank of the screw and the other flank can be cut by the cutting edge of the complete crest portion. Therefore, similarly to the cutting tap according to claim 1, there is an effect that the surface roughness of the flank on both sides of the female screw can be reduced.

  According to the cutting tap of claim 4, the biting portion has a biting triangle because the pointed triangle of the thread is formed in the same shape as the complete peak portion and is located on the axial center side with respect to the complete peak portion. Since the thread flank is formed by the cutting edge of the part, the flank of the thread is positioned closer to the axial center than the flank on both sides of the female thread to be cut into the work. In addition, after the thread portion forms a screw thread whose valley bottom is set for all the same leads, at least the thread portion that connects the chamfered portion and the complete thread portion transitions from the bited portion to the complete thread portion. By grinding the flank flank formed on the thread of the cutting blade immediately before starting, the lead of the flank flank is set larger than the lead of the female thread. Since it is cut by the cutting edge of the biting portion, the entire one flank and the other flank of the screw can be cut by the complete cutting edge. Therefore, similarly to the cutting tap according to claim 1, there is an effect that the surface roughness of the flank on both sides of the female screw can be reduced.

  In the cutting tap according to claim 5, in addition to the effect of the cutting tap according to any one of claims 1 to 4, the biting portion has an effective diameter of each screw thread set to the same dimension in the axial direction. And the top of the thread is cut off and inclined downward toward the axis toward the tip of the tool body, so by reducing the cutting torque on the tip side of the cutting tap, There is an effect that the biting of the cutting tap can be improved.

  Furthermore, since the biting portion can be formed by first forming a thread having the same effective diameter and then cutting off the top of the thread, the grinding wheel is moved in parallel along the rotational axis direction. It is possible to form a screw thread constituting the biting portion. Therefore, the grinding wheel is moved relative to the work piece in the axial direction, and compared with the case where the thread of the thread portion is cut while the grinding wheel is moved closer to the work piece. Since it is possible to prevent the grinding wheel from coming into contact with the center supporting the shaft of the workpiece and damaging the center, there is an effect that it is possible to improve the working efficiency when manufacturing the cutting tap.

It is a front view of the cutting tap in one embodiment of the present invention. It is the schematic diagram which represented typically the cross-sectional shape of the thread part containing the axis | shaft of a cutting tap. (A) is the schematic diagram which represented typically the locus | trajectory of the thread part of a biting part and a complete thread part, (b) is the cutting site | part by the thread part of a biting part and a complete thread part typically. FIG. (A) is the schematic diagram which represented typically the thread part in the conventional cutting tap, (b) is the schematic diagram which represented typically the locus | trajectory of the thread part of a biting part and a complete thread part. (C) is the schematic diagram which represented typically the cutting site | part by the thread part of a biting part and a complete thread part.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. First, the configuration of the cutting tap 100 will be described with reference to FIGS. 1 to 3. FIG. 1 is a front view of a cutting tap 100 according to an embodiment. FIG. 2 is a schematic diagram schematically showing the cross-sectional shape of the threaded portion 20 including the axis O of the cutting tap 100. In FIG. 2, the shape of the thread 50 (see FIG. 4B) of the female thread formed on the work piece by the cutting tap 100 is schematically illustrated by a broken line, and before chamfering is performed. The shape of the thread of the biting portion 21 is schematically illustrated by a two-dot chain line.

  The cutting tap 100 has a female screw in a prepared hole provided in a work piece by a rotational force transmitted from a processing machine (for example, a machining center) via a holder (not shown) and a feed suitable for the lead of the screw. 1, as shown in FIG. 1, a tool body 10 that is rotated around an axis O, a screw portion 20 that is provided on the tip side (right side in FIG. 1) of the tool body 10, It is a spiral tap provided with the groove | channel 30 recessedly provided in an outer peripheral surface.

  The tool body 10 is made of high-speed tool steel and is formed in a cylindrical shape having an axis O. The tool body 10 is not limited to high-speed tool steel, and may be made of a cemented carbide obtained by sintering tungsten carbide (WC).

  The screw part 20 is a part for performing cutting while rotating by the rotational force transmitted from the processing machine via the tool body 10, and the biting part 21 provided on the tip side and the biting part 21 And a complete mountain portion 22 provided continuously. Moreover, the screw part 20 is formed with the single thread | screw, and the lead of the biting part 21 and the complete peak part 22 is set to the dimension L (refer FIG. 2).

  The groove 30 is a part for discharging chips generated by the threaded portion 20 during the cutting process, and is formed as a so-called right twist groove that is twisted to the right with respect to the axis. A cutting edge 20 a is formed along the groove 30. Thereby, the chip | tip produced | generated at the time of a cutting process is discharged | emitted to the back side (FIG. 1 left side) of the tool main body 10 by the chip | tip discharge | emission effect | action of the groove | channel 30. FIG.

  As shown in FIG. 2, the biting portion 21 is a portion for cutting a female screw by cutting a prepared hole in the workpiece, and each screw thread 23 a to 23 c, 24 a of the biting portion 21. Is set to the same dimension over the axis O direction. Further, the tops of the screw threads 23 a to 23 c and 24 a of the biting portion 21 are cut off and inclined downward toward the axis O toward the tip of the tool body 10. Thereby, since the cutting torque of the front end side of the cutting tap 100 can be made small, the biting of the cutting tap 100 with respect to a workpiece can be improved. The biting portion 21 includes a first biting portion 23 formed from the front end side toward the rear end side, and a second biting portion 24 adjacent to the first biting portion 23 and the complete mountain portion 22. It has.

  The first biting portion 23 is a part for improving the biting of the cutting tap 100 with respect to the workpiece when forming a female screw on the workpiece, and the pointed triangle of the thread is the workpiece. Are formed in substantially the same shape as the pointed triangle of the female thread 50 (see FIG. 4B). Further, the lead of each of the screw threads 23a to 23c constituting the first chamfered portion 23 is set to the dimension L, the valley diameter is set to the diameter R1, and the effective diameter of the first chamfered portion 23 is set to the diameter R3. . Note that a radius of a virtual cylinder formed with the diameter R1 is a dimension r1, and a radius of the diameter R3 is r3.

  The second chamfered portion 24 is a portion that connects the chamfered portion 21 and the complete mountain portion 22, and the valley diameter on the first chamfered portion 23 side is set to the diameter R <b> 1, and The valley diameter is set larger than the diameter R1.

  The complete thread portion 22 is a part mainly improving the finishing of the flank of the female thread and the guide or self-guiding property in the process of cutting the female thread on the work, and the thread is formed on the work. The thread 50 of the female thread (see FIG. 4B) is formed in substantially the same shape as the pointed triangle. Further, in the complete mountain portion 22, the lead is set to the dimension L, the valley diameter is set to the diameter R2 having a larger dimension than the diameter R1, and the effective diameter of the complete mountain portion 22 is set to the diameter R4 having a larger dimension than the diameter R3. Has been. That is, the threaded triangle of the chamfered part 21 has the same shape as the threaded triangle of the complete threaded part 22, and the effective diameter of the chamfered part 21 is set to be smaller than the complete threaded part 22. Yes. The dimension of the diameter R2 is set to the same dimension as the inner diameter of the female screw formed on the work. Further, a radius of a virtual cylinder formed with the diameter R2 is a dimension r2, a radius of the diameter R4 is r4, and a difference between the dimensions r1 and r2 is a dimension y1.

  Next, a method for forming the threaded portion 20 when the cutting tap 100 is manufactured will be described. First, the thread portion 20 is formed with a groove 30, and the rake face formed by the groove 30 is polished to form the cutting edge 20 a (see FIG. 1), and then corresponds to the thread groove shape of the complete peak portion 22. It is formed by grinding using a grinding wheel (not shown) on which threads are formed.

  Specifically, first, the workpiece is rotated around the axis O while pressing the grinding wheel against the outer peripheral surface of the cylindrical workpiece, and the biting portion is formed from the tip side (right side in FIG. 2) of the workpiece. The grinding wheel is moved relative to the workpiece by the dimension in which 21 is formed, along the axis O direction, so that the lead has a dimension L toward the side where the complete peak portion 22 is formed. At this time, the grinding wheel is pressed so that the root diameter of the thread formed on the workpiece becomes the diameter R1.

  Subsequently, when the chamfered portion 21 is shifted to the complete crest portion 22, the grinding wheel is separated from the workpiece so that the root diameter of the thread formed on the workpiece is changed from the diameter R1 to the diameter R2. The bottom lead is moved along the axis O direction to the side where the complete peak portion 22 is formed so that the lead at the bottom of the valley is larger than the dimension L by x1. Thereby, the lead from the top of the thread of the second chamfered portion 24 to the top of the thread of the first chamfered portion adjacent to the second chamfered portion 24 can be set to the dimension L.

  Subsequently, while pressing the grinding wheel so that the root diameter of the thread formed on the workpiece becomes the diameter R2, the complete thread portion 22 is formed along the axis O direction with respect to the workpiece. The workpiece is moved so that the lead has a dimension L toward the side to be formed. After the grinding wheel has moved to the end of the position where the complete peak portion 22 is formed, the grinding wheel is again moved relative to the position where the complete peak portion 22 is formed from the front end side of the workpiece. These operations are repeatedly performed until the height of the thread of the screw portion 20 reaches a desired dimension. Thereby, the thread of the biting part 21 and the complete thread part 22 are formed.

  Next, the top of the screw thread formed in the portion constituting the biting portion 21 is cut off by a threading process. As a result, a tapered biting portion 21 that is inclined downward toward the axis O toward the distal end side is formed. Therefore, the biting portion 21 first forms a screw thread whose effective diameter is set to the same dimension in the direction of the axis O, and then cuts out the top of the screw thread to thereby form the screw threads 23a to 23c, 24a. Therefore, the thread of the biting portion 21 can be formed while moving the grinding wheel in parallel along the rotation axis direction. Therefore, the grinding wheel is relatively moved in the direction of the axis O with respect to the workpiece, and the thread of the screw portion 20 is cut while the grinding wheel is moved closer to the workpiece. Since it is possible to prevent the grinding wheel from coming into contact with a center (not shown) that supports the axis O of the workpiece and damage the center, it is possible to improve the working efficiency when manufacturing the cutting tap 100.

  Here, the cutting process by the screw part 20 will be described with reference to FIG. FIG. 3A is a schematic diagram schematically showing the trajectory of the chamfered portion 21 and the threads 23a to 23c, 24a, and 22a of the complete crest portion 22, and FIG. And it is the schematic diagram which represented typically the cutting site | part 23a1-23c1, 24a1, 22a1 by the thread 23a-23c, 24a, 22a of the complete thread part 22. FIG.

  As shown to Fig.3 (a), when forming an internal thread in the pilot hole provided in the workpiece, the thread 23a-23c, 24a, 22a of the biting part 21 and the complete thread part 22 is carried out by lead feeding. One flank 51 and the other flank 52 of the thread 50 of the female thread are formed by accumulating the cutting parts 23a1 to 23c1, 24a1, and 22a1 cut by the cutting blade 20a (see FIG. 1). .

  However, when performing the internal thread machining by the cutting tap 100, the chips are discharged to the rear side (left side in FIG. 3A) with respect to the traveling direction of the cutting tap 100 by the chip discharging action of the groove 30. Therefore, the cutting tap 100 is pushed out in the traveling direction (the right direction in FIG. 3A) by the reaction force of chip discharge. Therefore, as shown in FIG. 3B, when performing the internal thread machining by the cutting tap 100, the cutting tap 100 advances too much than the normal feed amount, and the cutting sites 23 a 1 to 23 c 1, 24 a 1 and 22 a 1 are formed on the cutting tap 100. The position shifts in the direction of travel. As a result, a step is formed on one flank 51 of the female thread 50 cut by the cutting edge 20a of the first biting portion 23, and irregularities are formed.

  On the other hand, as shown in FIG. 2, the diameter R3 (radius r3) that is the effective diameter of the biting portion 21 is set smaller than the diameter R4 (radius r4) that is the effective diameter of the complete peak portion 22. Therefore, since it is formed from the cutting edge 20a (see FIG. 1) of the biting portion 21, the flank of the screw is positioned closer to the axis O than the flank on both sides of the female screw to be cut on the work. In addition, since the crests of the bite portion 21 and the complete peak portion 22 are set to the same lead, the cutting edge 20a of the bite portion 21 is cut when the bite portion 21 is shifted to the complete peak portion 22. Therefore, the entire one flank and the other flank of the screw can be cut with the cutting edge 20a of the complete peak portion 22.

  Therefore, as shown in FIG. 3B, when cutting is performed by the cutting edge 20a (see FIG. 1) of the biting portion 21, one flank 51 of the thread 50 of the screw is stepped and unevenness is formed. Even so, since the cutting edge 20a of the full thread portion 22 is cut by the cutting edge 20a of the biting portion 21, one flank 51 of the thread 50 of the screw can be cut. The surface roughness of the flank 51 can be reduced.

  Further, when there is a lead error in the biting portion 21, the positional shift of the cutting parts 23a1 to 23c1 and 24a1 occurs, and as a result, the surface roughness of one flank 51 or the other flank 52 of the thread 50 of the female screw Even when the length becomes large, one of the flank 51 and the other flank 52 of the screw thread 50 can be cut by the cutting edge 20a of the complete thread portion 22 because it is cut by the cutting edge 20a of the biting portion 21. it can. Therefore, the surface roughness of the flank on both sides of the female screw can be reduced.

  When the inventor measured the surface roughness of the screw flank because it was cut by a conventional cutting tap 500 (M10 × 1.5, helix angle 35 degrees, flank angle 30 °, see FIG. 5), Rz = 5 It was 5-8.9 μm. On the other hand, since the cutting tap 100 (M10 × 1.5, helix angle 35 °, flank angle 30 °, radial dimension difference y = 0.034 mm, see FIG. 2) of the present invention is used, When the surface roughness was measured, it was Rz = 3.8 to 4.8 μm. Therefore, it became clear that the surface roughness of the female thread can be reduced by using the cutting tap 100 of the present invention.

In addition, when performing the cutting process by the cutting tap 100, the dimensional difference x2 (see FIG. 2) between the locus of the cutting edge 20a of the chamfered portion 21 and the locus of the cutting edge 20a of the complete peak portion 22 is used. The surface roughness Rz can be reduced. Since Rz is empirically 5 to 10 μm, when the thread of the threaded portion 20 has a flank angle α, the dimension y1 is set to 5 / tan α to 10 / tan α (μm), thereby leading the cutting tap 100. Due to an error in feeding, the unevenness of one flank 51 and the other flank 52 of the screw can be surely finished flat by the second biting portion 21. The dimension x1 is calculated by the following formula using the lead of the female screw and the dimension y1.
x1 = (L ² + y1 ² ) ^1/2 −L
However, the lead of the female screw is L.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It can be easily guessed.

  For example, although the case where the embodiment is used for a spiral tap has been described in relation to the present invention, the present invention is not necessarily limited thereto, and the present invention may be used for a point tap or a hand tap. Here, in the case of a point tap, since the chips are discharged in the traveling direction, the feed amount of the point tap may be delayed due to a reaction of chip discharge. At this time, the cutting part is displaced rearward with respect to the serious direction of the point tap, and as a result, the surface roughness of the flank of the female thread increases. However, since the outer diameter of the cutting edge 20a of the biting portion 21 is smaller than the outer diameter of the cutting edge 20a of the complete peak portion 22, in the cutting of the female thread flank by the cutting edge 20a of the biting portion 21, the female screw Even when the surface roughness of the flank increases, the surface roughness of the flank of the female thread can be reduced by the cutting edge 20a of the complete ridge 22.

  Furthermore, although the said embodiment demonstrated the case where the thread part 20 was formed with the single thread | thread, it may be formed with the double thread or the triple thread.

  In the above embodiment, when the cutting tap 100 is manufactured, the lead at the bottom of the valley is along the axis O direction so that the lead at the bottom of the valley becomes larger than the dimension L by x1 when shifting from the bite portion 21 to the complete peak portion 22. By moving to the side where the complete crest portion 22 is formed, from the top of the thread portion of the second chamfer portion 24 to the top of the screw portion of the first chamfer portion adjacent to the second chamfer portion 24 Although the case where the lead is set to the dimension L has been described, the present invention is not necessarily limited thereto, and at the time of manufacturing the cutting tap 100, after forming the screw thread 20 of the thread portion 20 in which the valley bottoms are all set to the same lead, Of the second chamfered portion 24, when the internal thread is cut, the follower flank of the thread of the cutting edge just before the transition from the chamfered portion 21 to the complete crest 22 is ground with a grinding wheel, and the follower flank is 24a2 It may be set to be larger than the de female thread of the lead. Accordingly, the thread flank is formed by the cutting edge 20a (see FIG. 1) formed at the ridge line between the follower side flank 24a2 and the groove 30, so that the flank of the screw is more than the flank on both sides of the female thread to be cut into the work piece. Therefore, when cutting from a chamfered part to a complete crest when cutting a female thread, it is cut by the cutting edge of the chamfered part so that one entire flank and the other flank of the screw are completely It can cut with the cutting edge of a mountain part, As a result, the surface roughness of the flank on both sides of a female screw can be made small. The amount of grinding of the trailing flank of the thread of the cutting edge immediately before the transition from the biting portion 21 to the complete ridge portion 22 is preferably about 10 μm in the direction perpendicular to the trailing flank.

  Here, in the second chamfered portion 24, when cutting the female screw, the thread of the cutting blade immediately before the transition from the chamfered portion 21 to the complete crest portion 22 is the rotation direction of the cutting tap 100. The first thread of the complete chamfer 22 (the thread of the complete crevice 22 located closest to the tip of the tool body 10) and the last thread of the second chamfer 24 adjacent through the groove 30 (most tool) This refers to the thread of the second chamfered portion 24 located on the rear end side of the main body 10. In this case, it is sufficient that at least the lead of the follower flank of the thread of the cutting edge just before the transition from the biting portion 21 to the complete crest portion 22 is set.

  Furthermore, in the above-described embodiment, the threaded triangle of the chamfered portion 21 has the same shape as the threaded triangle of the complete crest 22, and the chamfered portion 21 has an effective diameter greater than that of the complete crest 22. However, the present invention is not necessarily limited to this. If the effective diameter of the biting portion 21 is set smaller than the effective diameter of the complete peak portion 22, the biting portion 21 Since the thread flank is formed by the cutting edge and is positioned on the axial center side with respect to the flank on both sides of the female thread to be cut into the work, the sharp triangular shape of the threaded portion 21 is the thread of the complete thread portion 22. The shape may be different from the pointed triangle of the mountain. Further, if the pointed triangle of the threaded portion 21 has the same shape as the pointed triangle of the complete thread portion 22 and is located on the axial center side of the threaded triangle of the complete thread portion 22. Since the flank of the screw is formed by the cutting edge of the biting portion 21, the flank of the screw is located on the axial center side with respect to the flank on both sides of the female screw to be cut into the work piece. The relationship with the dimension of the effective diameter of the peak portion 22 does not matter.

  Moreover, in the said embodiment, although the case where it was the incomplete screw by which the thread removal process was given to the top of the thread 23a-23c, 24a of the biting part 21, it was not necessarily restricted to this, The screw threads 23a to 23c and 24a of the biting portion 21 may be complete screws. In this case, since the entire thread of the biting portion 21 is reduced in diameter toward the tip of the tool body 10, the screw portion 20 can be guided while biting inside the prepared hole of the workpiece.

  In the above-described embodiment, the case where each screw thread of the screw portion 20 is a triangular screw has been described. It may be a screw. Further, each thread may be provided with a relief whose outer diameter decreases from the cutting edge 20a toward the heel.

100,500 Cutting tap 10 Tool body 20,520 Threaded portion 20a Cutting edge 21,521 Chamfered portion 22,522 Complete crest portion 24 Second chamfered portion (thread that connects chamfered portion and complete crest portion)
24a2 Follow-up flank 30 Groove 50 Female thread thread O-axis

Claims (5)

A tool body that is rotated around an axis, a threaded portion that is provided on the tip side of the tool body, and a screw portion that has a complete crest portion that is continuous with the bited portion, and a recess formed on the outer peripheral surface of the threaded portion. A cutting tap that includes a groove formed and a cutting edge formed in the thread portion along the groove,
The bite portion is set to have an effective diameter smaller than each of the complete mountain portions,
The root of the valley bottom connecting the biting part and the complete thread part is set larger than the lead of the female thread, so that the thread peaks of the thread part are all set to the same lead. And a cutting tap. A tool body that is rotated around an axis, a threaded portion that is provided on the tip side of the tool body, and a screw portion that has a complete crest portion that is continuous with the bited portion, and a recess formed on the outer peripheral surface of the threaded portion. A cutting tap that includes a groove formed and a cutting edge formed in the thread portion along the groove,
The biting part is formed in the same shape as the complete mountain part with a pointed triangular thread, and is located on the axial center side with respect to the complete mountain part,
The root of the valley bottom connecting the biting part and the complete thread part is set larger than the lead of the female thread, so that the thread peaks of the thread part are all set to the same lead. And a cutting tap. A tool body that is rotated around an axis, a threaded portion that is provided on the tip side of the tool body, and a screw portion that has a complete crest portion that is continuous with the bited portion, and a recess formed on the outer peripheral surface of the threaded portion. A cutting tap that includes a groove formed and a cutting edge formed in the thread portion along the groove,
The bite portion is set to have an effective diameter smaller than each of the complete mountain portions,
The screw portion is formed of a screw thread whose valley roots are all set to the same lead, and among the screw threads that connect the biting portion and the complete thread portion, at least the biting portion to the complete thread portion. A cutting tap, wherein the follower flank lead is set to be larger than the lead of the female thread by grinding the follower flank formed on the thread of the cutting edge immediately before the transition to. A tool body that is rotated around an axis, a threaded portion that is provided on the tip side of the tool body, and a screw portion that has a complete crest portion that is continuous with the bited portion, and a recess formed on the outer peripheral surface of the threaded portion. A cutting tap that includes a groove formed and a cutting edge formed in the thread portion along the groove,
The biting part is formed in the same shape as the complete mountain part with a pointed triangular thread, and is located on the axial center side with respect to the complete mountain part,
The screw portion is formed of a screw thread whose valley roots are all set to the same lead, and among the screw threads that connect the biting portion and the complete thread portion, at least the biting portion to the complete thread portion. A cutting tap, wherein the follower flank lead is set to be larger than the lead of the female thread by grinding the follower flank formed on the thread of the cutting edge immediately before the transition to. The chamfered portion is configured such that the effective diameter of each screw thread is set to the same dimension in the axial direction, and the top of the screw thread is cut off and inclined downward toward the axis toward the tip of the tool body. The cutting tap according to claim 1, wherein the cutting tap is formed.

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