JP2006255862A - Spiral tap - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spiral tap which can excellently cut a female screw even if chippings are squeezed into a prepared hole. <P>SOLUTION: According to the structure of the spiral tap, a projective center 18 is formed at a front end of a screw portion 16, and a gash 24 is formed in the projective center 18. Therefore when the screw portion 16 is screwed into the prepared hole to cut the female screw, chippings present in the prepared hole are scraped out by the gash 24 to be adequately discharged via a twist groove 20 toward a shank 12. Thus increased tap machining torque due to clogging of the prepared hole with chippings, and tap breakage caused by bite in chippings at the time of counter-rotation, are suppressed. Further the spiral tap only has the projective center 18 formed at the front end of the screw portion, and therefore compared with a conventional tap with a drill, a projective dimension is small. As a result, a useless space on the bottom of a screw hole, which is necessary when a closed end screw hole is machined, is reduced, which enables the machining of the female screw to the vicinity of the bottom, and therefore limitations on machining conditions are eased. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a spiral tap, and more particularly to a spiral tap that can satisfactorily cut a female screw even in a state where chips enter a pilot hole.

(a) a threaded portion in which a cutting edge is formed along a torsion groove provided to divide the male screw, and (b) a diameter smaller than that threaded portion and concentric with the threaded portion. And (c) the threaded portion is screwed into the pilot hole, so that the cutting edge cuts into the inner peripheral surface of the pilot hole. For example, Patent Document 1 discloses a spiral tap that cuts a female screw and discharges chips to the shank side by the twist groove. Further, Patent Document 2 proposes a tap with a drill in which a drill is provided on the tip side of a threaded portion, and a pilot hole is drilled by the drill, and a female screw is cut continuously after the pilot hole processing. Yes.
JP-A-2005-7527 Japanese Patent Laid-Open No. 10-100020

  By the way, when cutting a large number of screw holes in a large cast article with a portal type processing machine, etc., it may be difficult to use cutting oil, and it may not be possible to wash off the drilling chips. If tapping is performed with fine chips in the hole, even conventional spiral taps cannot discharge the chips sufficiently, which may result in clogging of chips or biting of chips when reversing. There was a problem that the tap was broken. For this reason, at present, tapping is performed after removing chips manually by vacuum or the like after drilling, and labor and time are required and automation by unmanned operation cannot be performed.

  On the other hand, it is conceivable to use a tap with a drill to cut a female thread continuously after drilling a pilot hole, but since there is a drill on the tip side of the threaded part that cuts the female thread, When a hole is machined, useless space for a drill is required at the bottom of the screw hole, and a female screw cannot be provided near the bottom, and may not be used depending on machining conditions. As described above, the intrusion of chips into the prepared hole becomes a problem when a bottomed screw hole is processed normally, and a tap with a drill may not be used.

  The present invention has been made in the background of the above circumstances, and an object of the present invention is to provide a spiral tap that can satisfactorily cut a female screw even in a state in which chips enter a pilot hole.

  In order to achieve such an object, the first invention comprises (a) a threaded portion in which a cutting edge is formed along a twisted groove provided so as to divide the male thread, A neck having a small diameter and being concentrically provided with the threaded portion, and wherein the twisted groove is formed continuously with the threaded portion, and (c) by screwing the threaded portion into the pilot hole A spiral tap that cuts a female thread on the inner peripheral surface of the pilot hole by the cutting blade and discharges chips to the shank side by the torsion groove, and (d) axially toward the tip side of the threaded portion. A conical projecting center provided concentrically so as to project, and wherein the twisted groove is formed continuously with the threaded portion; and (e) a side wall on the cutting edge side of the twisted groove of the projecting center. Gash provided in Characterized in that it.

  According to a second aspect of the present invention, in the spiral tap of the first aspect, the gash is a straight or spiral gash, and is provided with a cutting angle γ within a range of 5 ° to 20 ° with respect to the generatrix of the cone of the protruding center. It is characterized by.

  3rd invention is a spiral tap of 1st invention or 2nd invention, (a) It is for cutting a female thread with respect to the pilot hole provided in casting, (b) The twist groove | channel in the said thread part The torsion angle β is in the range of 30 ° to 50 °, the number of cutting edges is two, the tip angle θ of the protruding center is in the range of 80 ° to 100 °, and the length of the thread portion L is in the range of 7 to 10 pitches of the external thread, and the diameter d of the neck is in the range of 50% to 70% of the nominal diameter D.

  In such a spiral tap, a conical protruding center is provided on the tip side of the threaded portion, and the protruding center is provided with a gash on the side wall on the cutting edge side of the torsion groove. When the female screw is cut by being screwed into the hole, the chips in the pilot hole are scraped out by the gash and are well guided into the twisted groove, and are discharged from the twisted groove to the shank side. This suppresses tap breakage caused by increased tapping torque due to chip clogging and biting of chips during reversal, eliminating chip removal work after drilling and automating unattended operation. It becomes possible. In addition, since only the conical protruding center is provided at the tip of the threaded portion, the protruding size can be smaller than that of a conventional drilled tap, and the screw hole when machining a bottomed screw hole is required. The useless space at the bottom is reduced, so that the internal thread can be cut to near the bottom, and the restrictions on the processing conditions are eased.

  In the second aspect of the invention, since the gash is provided at a cutting angle γ within the range of 5 ° to 20 ° with respect to the conical generatrix of the projecting center, the scraping action for guiding the chips into the twisted groove can be obtained satisfactorily. .

  The third invention is a spiral tap for internal thread machining on a casting, and generally the chips of the casting are finely divided. Therefore, the chips in the pilot hole can be scraped out by the gash and discharged well. Further, when the twist angle β of the twist groove in the threaded portion is in the range of 30 ° to 50 °, the number of cutting edges is two, and the tip angle θ of the protruding center is in the range of 80 ° to 100 °. Since the length L of the part is within the range of 7 to 10 pitches of the external thread and the diameter d of the neck is within the range of 50% to 70% of the nominal diameter D, a sufficient chip storage capacity is ensured. While avoiding chip clogging, the projecting center can be pushed into the prepared hole clogged with chips while scraping out the chips by gashes and discharged to the shank side by the twist groove.

  The present invention is preferably applied to a spiral tap in which a shank, a neck portion, a threaded portion, and a protruding center are provided coaxially and integrally in that order. It may be fixed integrally by shrink fitting, screws or the like. As the base material of the spiral tap, various tool materials such as high-speed tool steel (high speed) and cemented carbide can be used, and if necessary, a hard coating such as TiAlN, TiN, or TiCN may be coated. it can.

  The spiral tap of the present invention has a chip filled with chips, especially when the internal thread is cut by dry machining on a cast such as gray cast iron, and the chips are also piled up on the workpiece. However, it can also be used when a female thread is cut into another work material. It is also possible to use in wet processing in which tapping is performed while sufficiently supplying the lubricant.

  The gash provided at the projecting center is provided by, for example, grinding or cutting with a grinding wheel, and the cross-sectional shape thereof is a V-shaped cross section having an angle of, for example, about 90 ° to 120 °. Other cross-sectional shapes can also be used. The gash is provided, for example, so as to intersect with the side wall of the torsion groove in the vicinity of the boundary between the protruding center and the threaded portion, but the gash may penetrate to the threaded portion.

  For example, in the case of a two-blade spiral tap, the gash is preferably provided from the vicinity of the center of the projecting center so that the center thickness t, which is the distance between the pair of gashes, is in the range of 0.5 mm to 1.0 mm. However, the center thickness t can be made larger than 1.0 mm by, for example, the nominal diameter D or the cutting angle γ.

  If the cut angle γ of the gasche is less than 5 °, a predetermined scraping effect cannot be obtained. On the other hand, if it is greater than 20 °, the strength of the protruding center is reduced. It can also be set outside the range of 5 ° to 20 ° depending on the angle θ, the nominal diameter D, the center thickness t, and the like.

  The twist angle β of the twist groove in the threaded portion is preferably within a range of 30 ° to 50 ° in terms of chip dischargeability. The number of cutting blades is preferably two in order to secure a chip storage capacity. If the tip angle θ of the projecting center is smaller than 80 °, the projecting dimension becomes longer and it is easy to hit the bottom of the blind hole. On the other hand, if it is larger than 100 °, the chips are difficult to push away and the tapping load increases. A range of ˜100 ° is desirable. When the length L of the threaded portion is less than 7 pitches of the external thread, the guideability is impaired. On the other hand, when the length is longer than 10 pitches, chip clogging is likely to occur. Therefore, the range of 7 to 10 pitches is desirable. When the diameter d of the neck is less than 50% of the nominal diameter D, the strength is reduced. On the other hand, when the diameter is more than 70%, the chip passage becomes narrow and the discharge performance is deteriorated. Is desirable. However, it can also be determined outside the above range depending on the relationship between the setting elements and the processing conditions.

  It is desirable that the torsion groove provided across the neck, the threaded portion, and the projecting center is provided so that the lead is constant for ease of manufacturing, and in that case, the torsion angle increases with the difference in diameter. Although it changes, it is also possible to provide a torsion groove so that the torsion angle is constant regardless of the difference in diameter.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1A and 1B are diagrams showing a two-blade spiral tap 10 for casting, which is an embodiment of the present invention. FIG. 1A is a front view seen from a direction perpendicular to the axis, and FIG. (C) is an end view of (b) as viewed from the tip side, and (d) is a cross-sectional view of the gasche 24. FIG. 2 is a photograph of the spiral tap 10, in which (a) corresponds to FIG. 1 (a), but only the tip side portion is copied, and (b) is shown in FIG. 1 (b). Correspondingly, (c) is a copy of the gasche 24 from the tap tip side.

  The spiral tap 10 is integrally provided with a shank 12, a neck portion 14, a screw portion 16, and a protruding center 18 on the same axis in that order, and the screw portion 16 has a screw groove corresponding to a female screw to be processed. A male screw having a shape is provided, and a pair of torsion grooves 20 are provided symmetrically with respect to the axis so as to divide the male screw. The threaded portion 16 includes a chamfered portion 16a on the tip side from which the thread is removed in a tapered shape, and a complete threaded portion 16b of a complete thread provided continuously to the chamfered portion 16a. A cutting edge 22 is provided at a ridge line portion with the twist groove 20. The rake angle of the cutting edge 22 is about 2 ° to 4 °. In addition, the conical protruding center 18 protruding forward from the biting portion 16a has a gash 24 so that the opening edge portion of the side wall on the cutting edge 22 side of the twist groove 20 is removed in a V shape (saddle shape). , And intersects the side wall of the twist groove 20 near the boundary between the protruding center 18 and the threaded portion 16. The pair of torsion grooves 20 are continuously provided in a continuous manner from the projecting center 18 to the threaded portion 16 and the neck portion 14 along a certain lead winding. The groove bottom diameter of the torsion groove 20 is substantially constant, but in this embodiment, the diameter decreases toward the shank 12 with a gradient of about 1/80.

  The name of the spiral tap 10 is M6 × 1, that is, for cutting a right-handed female screw having a valley diameter of 6 mm and a pitch of 1 mm, and is composed of high-speed tool steel (powder high speed). The neck portion 14, the screw portion 16, and the protruding center 18 are coated with a TiCN film including the twisted groove 20. The diameter dimension of the thread portion 16 is a nominal diameter D (= 6 mm), the diameter dimension of the shank 12 is substantially the same as that of the thread portion 16, and the diameter dimension (neck diameter) d of the neck portion 14 is 50% to 70% of the nominal diameter D. %, In this example 3.5 mm (about 58% of D). The twist groove 20 in the threaded portion 16 is right-handed, and the twist angle β is in the range of 30 ° to 50 °, and is about 43 ° in this embodiment. The tip angle θ of the projecting center 18 is in the range of 80 ° to 100 °, and is 85 ° in the present embodiment, and the length (screw length) L of the screw portion 16 is in the range of 7 to 10 pitches of the male screw. In this embodiment, the pitch is 9 pitches. The length of the biting portion 16a is 3 pitches, and the length of the complete peak portion 16b is 6 pitches.

  On the other hand, the gash 24 is centered at the tip end of the projecting center 18 so that the center thickness t, which is the distance between the pair of gashes 24, is in the range of 0.75 mm to 0.65 mm in the end view of FIG. The straight gash is provided in parallel with the shaft center from the vicinity, and the cutting angle γ with respect to the conical generatrix of the projecting center 18 is in the range of 5 ° to 20 °, and is 12.5 ° in this embodiment. That is, in this embodiment, since the tip angle θ of the protruding center 18 is 85 °, the cone bus angle is 85 ° / 2 = 42.5 °, and 42.5 ° -12.5 ° with respect to the axis. The gash 24 is provided by moving the grinding wheel relatively in the axial direction of the spiral tap 10 while being separated from the axial center of the spiral tap 10 so as to be inclined at = 30 °. Further, the gash groove angle φ corresponding to the shape of the grinding wheel is φ = 110 °, and the rake angle α in the circumferential direction is in the range of 7 ° to 9 °. FIG. 1C is a cross-sectional view perpendicular to the gasche 24.

  In such a spiral tap 10, a conical protruding center 18 is provided on the tip side of the screw portion 16, and the protruding center 18 has a gash 24 at the opening edge portion of the side wall on the cutting edge 22 side of the twisted groove 20. Therefore, when the threaded portion 16 is screwed into the pilot hole and the female screw is cut, the chips in the pilot hole are scraped out by the gash 24 and are well guided into the twist groove 20. It is discharged from the twisted groove 20 to the shank 12 side. This prevents tap breakage caused by increased tapping torque due to chip clogging and chip biting during reversal, eliminating chip removal after drilling and enabling automation by unmanned operation It becomes. Further, since only the conical projecting center 18 is provided at the tip of the threaded portion 16, the projecting dimension can be smaller than that of a conventional tap with a drill, and a screw for machining a bottomed screw hole. The useless space at the bottom of the hole is reduced, so that the internal thread can be cut to near the bottom, and the restrictions on the processing conditions are eased.

  Further, in this embodiment, since the gash 24 is a straight gash parallel to the axis, the gash 24 can be easily processed by relatively moving the grinding wheel in the axial direction without rotating the spiral tap 10. In addition, since the cutting angle γ of the gasche 24 is in the range of 5 ° to 20 °, the scraping action for guiding the chips into the twisted groove 20 can be obtained satisfactorily.

  Moreover, although the spiral tap 10 of the present embodiment is for castings, generally the chips of the casting are finely divided, so that the chips in the pilot hole can be scraped out by the gash 24 and discharged well. In addition, the twist angle β of the twist groove 20 in the threaded portion 16 is in the range of 30 ° to 50 °, the number of cutting edges 22 is two, and the tip angle θ of the protruding center 18 is in the range of 80 ° to 100 °. The thread length L of the thread portion 16 is within the range of 7 to 10 pitches of the male thread, and the diameter dimension d of the neck portion 14 is within the range of 50% to 70% of the nominal diameter D. While ensuring sufficient volume and avoiding chip clogging, the projecting center 18 is pushed into the prepared hole clogged with chips while scraping out the chips by the gash 24, and by the twist groove 20 to the shank 12 side. Can be discharged.

FIG. 3 shows an M6 × 1 female thread similar to the spiral tap 10 described above. The twist angle β, the number of cutting edges 22, the tip angle θ of the protruding center 18, the screw length L, the neck diameter d, and the gasche 24 It is a figure which shows the result of having prepared 14 types of test products No1-No14 from which the cutting angle (gamma) differs, and having done the durability test on the following process conditions.
(Processing conditions)
・ Work material: FC250 (Gray cast iron)
・ Tapping depth: 7mm
・ Prepared hole depth: 18mm (full of chips + piled up on workpiece)
-Pilot hole diameter: 5.0 mm
・ Cutting oil: Dry ・ Cutting speed: 10 m / min

  The shaded portions in FIG. 3 are setting elements that are considered to be the causes of the tool life. For convenience, the same reference numerals as those of the spiral tap 10 will be used to explain the twist angle β of the twist groove 20. In the test products No. 1 and No. 2 of 25 ° or less, the chip discharging action by the twist groove 20 was not sufficiently obtained, and the tap was broken due to the biting of the chips when the second hole and the 10th hole were reversed. When the twist angle β is 35 ° or 45 °, the chip discharging action by the twist groove 20 can be sufficiently obtained. As is apparent from the test pieces Nos. 3, 4, 6, 13, and 14, If the value of the setting element is appropriate, sufficient durability can be obtained.

  In the test sample No. 5 having three blades, the cross-sectional area (chip content) of each torsion groove 20 is small, so that sufficient chip discharge performance cannot be obtained, and chips are not removed when the second hole is reversed. The tap was broken by biting. When the number of blades is two, the cross-sectional area of each torsion groove 20 becomes large, and sufficient chip discharge performance can be obtained. As is clear from the test pieces Nos. 3, 4, 6, 13, and 14. If the values of other setting elements are appropriate, sufficient durability can be obtained.

  In the test sample No. 7 having a tip angle θ of 110 °, the thrust resistance when the protruding center 18 pushes away the chips and enters the prepared hole increases, so that the tapping torque increases accordingly, and the forward rotation of the 45th hole The tap was broken. When the tip angle θ is 85 ° or 95 °, the protruding center 18 easily enters the chip, and the tapping torque is reduced. As is apparent from the test pieces Nos. 3, 4, 6, 13, and 14, If the values of other setting elements are appropriate, sufficient durability can be obtained.

  In the test product No. 8 in which the length (screw length) L of the screw portion 16 is 6 pitches, the guiding action at the time of tapping by the screw portion 16 is lowered, and a predetermined female screw accuracy cannot be obtained. Further, in the test product No. 9 in which the length L of the screw portion 16 is 12 pitches, the chip discharging performance near the screw portion 16 is lowered and the chips are easily clogged, and the tap is broken during the forward rotation of the 32nd hole. When the length L of the thread portion 16 is 9 pitches, the thread portion 16 can provide a predetermined guiding action and a sufficient chip discharge performance, and the test products No. 3, 4, 6, 13, As is clear from FIG. 14, sufficient durability can be obtained if the values of the other setting elements are appropriate.

  In the test product No. 10 in which the diameter dimension (neck diameter) d of the neck portion 14 is 2.4 mm (0.4D), sufficient strength was not obtained, and the tap was broken during the forward rotation of the first hole. Further, in the test product No. 11 in which the diameter d of the neck portion 14 is 4.7 mm (0.78 D), the chip discharging performance in the neck portion 14 is lowered, and the tap is broken due to the biting of the chips when the tenth hole is reversed. . When the diameter d of the neck 14 is 3.5 mm (0.58 D), a predetermined strength can be obtained and sufficient chip discharging performance can be obtained, and the test products No. 3, 4, 6, 13, As is clear from FIG. 14, sufficient durability can be obtained if the values of the other setting elements are appropriate. “%” Shown in FIG. 3 is a ratio to the nominal diameter D.

  In the test product No. 12 in which the cutting angle γ of the gash 24 was 0 °, that is, when the gash 24 was not present, the chips in the pilot hole could not be scraped and discharged, and the tap was broken during normal rotation of the first hole. When the cutting angle γ is 7.5 °, 12.5 °, and 17.5 °, the chips in the pilot hole can be scraped out and discharged, which is apparent from the test pieces Nos. 3, 4, 6, 13, and 14. As described above, sufficient durability can be obtained if the values of the other setting elements are appropriate.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this is an embodiment to the last, and this invention implements in the aspect which added various change and improvement based on the knowledge of those skilled in the art. Can do.

(A) is a front view, (b) is an enlarged view of a tip side portion, (c) is an end view of (b) as seen from the tip side, d) is a cross-sectional view perpendicular to the gasche. FIG. 2 is a view showing a photograph of the spiral tap of FIG. 1, (a) is an appearance photograph of the tip side portion, (b) is an enlarged photograph of the tip portion, and (c) is an enlarged photograph of Gash. It is a figure which shows the result of having performed the durability test using 14 types of test goods which changed the value of various setting elements.

Explanation of symbols

  10: Spiral tap 12: Shank 14: Neck part 16: Screw part 18: Protruding center 20: Twist groove 22: Cutting edge 24: Gash

Claims (3)

A threaded portion in which a cutting edge is formed along a twisted groove provided to divide the male screw;
A neck having a smaller diameter than the threaded portion and concentric with the threaded portion, and the neck where the twisted groove is formed continuously with the threaded portion;
A spiral tap that cuts a female thread on the inner peripheral surface of the pilot hole by the cutting blade and discharges chips to the shank side by the twist groove when the threaded portion is screwed into the pilot hole In
A conical projecting center provided concentrically so as to project in the axial direction at the tip side of the threaded portion, and the twisted groove formed continuously to the threaded portion;
A gash provided on a side wall on the cutting edge side of the twist groove of the projecting center;
Spiral tap characterized by having. 2. The spiral tap according to claim 1, wherein the gash is a straight or spiral gash and is provided with a cutting angle γ within a range of 5 ° to 20 ° with respect to a conical generatrix of the projecting center. It is for cutting female threads against the pilot holes provided in the casting,
The twist angle β of the twist groove in the thread portion is within a range of 30 ° to 50 °, the number of cutting blades is two, and the tip angle θ of the protruding center is within a range of 80 ° to 100 °. The length L of the screw portion is within a range of 7 to 10 pitches of the male screw, and the diameter d of the neck portion is within a range of 50% to 70% of a nominal diameter D. The spiral tap according to 1 or 2.

Images