Cutting tap

Abstract

[Problem] To provide a tap with which it is possible to minimize chipping of a cutting edge, caused by swarf being generated, at a full thread portion even in the case when cutting work is done by the entirety of a biting portion located at the tip of the tap. [Solution] A tap 100 comprises: a biting portion 10 having multiple threads that perform screw machining on a machining subject material; a full thread portion 20 having a cutting edge that is formed contiguous from the biting portion 10; and a groove portion which is disposed in the biting portion 10 and the full thread portion 20 and which discharges swarf of the machining subject material. Regarding the relationship among the nominal diameter D0, root diameter D1, pitch P, and thread height h of the tap 100, formula (1): D1≥D0-P and formula (2): h≤P / 2 are simultaneously fulfilled.

Description

[Technical Field]

[0001] The present invention performs thread machining by cutting. cutting Regarding tapping. [Background technology]

[0002] Until now, thread machining by cutting required special tools, so-called cutting This was done using taps. cutting The cutting process is performed at the chamfer at the tip of the tap, and the chips generated by the cutting process pass through the groove (helical groove), cutting The chips are sent to the full thread portion at the rear end of the tap and discharged to the outside. At this time, the chips generated are formed in a spiral shape and have a relatively constant length, so as shown in Patent Documents 1 to 5, for example, part of the full thread portion is chamfered to enable the chips to be discharged more quickly.

[0003] on the other hand, cutting A valley is formed between the peaks that make up the chamfer of a tap, and the bottom of the groove is formed with a slight curve (a schematic cross-sectional view of the tip of a conventional tap 1 is shown in Figure 8). In other words, cutting by the chamfer is not performed in the valley (especially the bottom of the groove), so intermittent cutting of the workpiece can cause the problem of burrs forming around the screw hole in some workpieces.

[0004] To address this issue, it has been disclosed that by shaping the tap so that cutting can be performed even on the valleys of the chamfer (particularly the groove bottom), a so-called form machining of the entire chamfer can be performed, thereby suppressing burrs from occurring in the screw holes in the workpiece (see Patent Document 6). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2008-075402 [Patent Document 2] International Publication No. 2008-136123 [Patent Document 3] Japanese Patent Publication No. 2008-272856 [Patent Document 4] Japanese Utility Model No. Hei 10-286723 [Patent Document 5] Japanese Patent No. 2813173 [Patent Document 6] International Publication No. 1997-026106 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when cutting is performed using the entire chamfer, the chips become longer and the curl diameter becomes larger than when using conventional taps. As a result, when the chips are discharged to the outside, the chips get caught in the full crest part that hits the rear end of the tap, causing chipping or chipping of the cutting edge.

[0007] Therefore, in the present invention, cutting Even when cutting is performed over the entire chamfer at the tip of the tap, chipping of the cutting edge at the full threads due to chips generated can be suppressed. cutting The objective is to provide a tap. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, cutting The tap has at least a chamfering portion having a plurality of threads for threading a workpiece, a complete thread portion having a cutting edge formed continuously from the chamfering portion, and grooves provided in the chamfering portion and the complete thread portion for discharging chips from the workpiece. cutting In the tap, cutting The relationship between the tap nominal diameter D0, root diameter D1, pitch P, and thread height h must simultaneously satisfy the following formulas (1) and (2). cutting Tap. D1≧D0−P (1) h≦P / 2 (2)

[0009] The cutting edges of the complete thread portion can be chamfered. In particular, it is preferable to chamfer the cutting edges of the second and subsequent threads of the complete thread portion. In this case, it is more preferable to chamfer all or part of the cutting edges of the complete thread portion except for the roots. [Effects of the Invention]

[0010] The present invention cutting The tap has the effect of being able to suppress chipping of the cutting edge at the full crest portion due to chips generated even when cutting is performed using the entire chamfer portion at the tip. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a front view of a cutting tap 100 (first embodiment) of the present invention. [Figure 2] FIG. 2 is a left side view of the cutting tap 100 shown in FIG. [Figure 3] FIG. 2 is a perspective view of the cutting tap 100 shown in FIG. [Figure 4] 1 is a schematic cross-sectional view of a tip portion of a cutting tap 100 according to the present invention. [Figure 5] FIG. 2 is a schematic cross-sectional view parallel to the rotation axis of a cutting tap 200 (second embodiment) of the present invention. [Figure 6] FIG. 2 is a schematic cross-sectional view parallel to the rotation axis of a cutting tap 300 (third embodiment) of the present invention. [Figure 7] FIG. 2 is an enlarged view of the tip portion of the cutting tap 100 shown in FIG. [Figure 8] 8 is a cross-sectional view taken along line AA of the cutting tap 100 shown in FIG. 7. [Figure 9] 8 is a cross-sectional view of the cutting tap 100 shown in FIG. 7 along the line BB. [Figure 10] FIG. 2 is an enlarged view of a tip portion of a cutting tap 400 (fourth embodiment) of the present invention. [Figure 11] 11 is a cross-sectional view taken along line CC of the cutting tap 400 shown in FIG. 10. FIG. [Figure 12] 11 is a cross-sectional view of the cutting tap 400 shown in FIG. 10 taken along the line DD. [Figure 13] 1 is a schematic cross-sectional view of a workpiece cut by the invention product 1 in Example 1. FIG. [Figure 14] FIG. 2 is a schematic cross-sectional view of a workpiece cut by a conventional cutting process in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention cutting Various embodiments of the tap will be described with reference to the drawings. cutting FIG. 1 is a front view of the tap 100 of the first embodiment shown in FIG. cutting 2 and 1, a left side view of the tap 100 is shown. cutting A perspective view of the tap 100 is shown in FIG. cutting As shown in FIGS. 1 and 3, the tap 100 is roughly divided into a chamfer 10 at the tip side, which first performs thread cutting on a workpiece, a complete thread portion 20 formed continuously from the chamfer 10, and cutting The tap 100 is composed of a shank 90 located at the rear end side of the tap 100 and serving as a gripping portion when attached to a machine tool.

[0013] cutting The tap 100 is made up of cutting edges 51, 52, and 53 that are continuously formed from the chamfer 10 to the full crest 20 as shown in FIGS. 1 to 3. cutting A plurality of grooves 31, 32, and 33 formed spirally along the axial direction (longitudinal direction) of the tap 100 are adjacent to the cutting edges 51, 52, and 53. cutting It is disposed on the front side in the rotation direction of the tap 100 (clockwise direction in FIG. 2).

[0014] As shown in Figures 1 to 3 cutting A schematic cross-sectional view of the tap 100 in the axial direction along the root of the thread from the chamfer 10 to the full thread portion 20 ( cuttingFIG. 4 shows the upper half of the tap 100 from the rotation axis O1. cutting As shown in FIG. 4, the tap 100 has, from left to right in the drawing, a plurality of threads 11, 12 that form a part of the chamfer 10 and a plurality of threads 21, 22, 23 that form a part of the full thread portion 20. cutting In the axial direction of the tap 100, valleys 13, 14 are formed between two adjacent threads 11, 12 in the chamfer portion 10, and valleys 24, 25 are formed between three adjacent threads 21, 22, 23 in the full thread portion 20, respectively.

[0015] In addition, the present invention cutting The tap 100 is as shown in FIG. cutting When the nominal diameter of the tap 100 is D0, the diameter of the root of the root portion (root diameter) is D1, the pitch of the thread is P, and the height of the thread (the dimension from the root to the top of the thread) is h, the following formulas (1) and (2) are both valid. D1 ≥ D0 − P (1), h≦P / 2 (2)

[0016] In addition, as shown in Figure 4 cutting The tap 100 (first embodiment) has the following features: cutting 5. In the cross-sectional view of the tap 100, the bottom of the tap 100 is a straight line parallel to the rotation axis O1. However, if the above-described formula (1) and formula (2) are satisfied simultaneously, for example, as shown in FIG. cutting The tap 200 (second embodiment) has a configuration in which the bottom of the valley portion is formed by a plurality of straight lines, and the tap 200 shown in FIG. cutting The tap may have a configuration in which the bottom of the valley portion is formed by a curve, as in the tap 300 (third embodiment).

[0017] As shown in Figure 1 cutting An enlarged view of the tip portion of the tap 100 (first embodiment) is shown in FIG. 7, a cross-sectional view of the first thread 21 of the complete thread portion 20 shown in FIG. 7 taken along the AA cutting line is shown in FIG. 8, and a cross-sectional view of the second thread 22 of the complete thread portion 20 taken along the BB cutting line is shown in FIG. cuttingAs shown in FIGS. 7 and 8, the tap 100 does not have a chamfered portion (chamfered portion) on the cutting edge 51 of the first thread 21 of the complete thread portion 20.

[0018] On the other hand, from the second thread 22 onward of the complete thread portion 20, chamfered portions 41, 42, 43 are formed along the spiral flutes 31, 32, 33 on the entire cutting edges 51, 52, 53 as shown in Figures 7 and 9. cutting By chamfering the entire cutting edge of the second and subsequent threads in the fully threaded portion of the tap, chipping (loss) of the cutting edge of the fully threaded portion can be prevented during thread machining.

[0019] Next, different embodiments of the present invention cutting An enlarged view of the tip portion of the tap 400 (fourth embodiment) is shown in FIG. cutting 11 and 10 show cross-sectional views of the first thread 321 of the complete thread portion 320 of the tap 400 taken along the CC cutting line. cutting FIG. 12 shows a cross-sectional view of the second thread 322 of the fully threaded portion 320 of the tap 400 taken along the line DD. cutting The tap 400 is also the same as that of the first embodiment. cutting As in the case of the tap 100, as shown in FIGS. 10 and 11, there is no chamfered portion (chamfered portion) on the cutting edge 351 of the first thread 321 of the full thread portion 320.

[0020] On the other hand, from the second thread 322 onward of the complete thread portion 320, chamfered portions 341, 342, 343 are formed at a plurality of locations along the spiral grooves 331, 332, 333 for each cutting edge 351, 352, 353 as shown in Figures 10 and 12. In this case, the chamfering of each cutting edge 351, 352, 353 is performed on the cutting edge except for the root of the complete thread portion. As in this embodiment, cutting By providing chamfering to the cutting edges of the second and subsequent threads in the complete thread portion of the tap, cutting As with the tap 100, chipping (fracture) of the cutting edge of the complete thread portion during thread machining can be prevented. [Example]

[0021] Two types of the present invention cutting Taps (hereinafter referred to as "Invention 1" and "Invention 2") and conventional cutting By conducting cutting tests using taps (hereinafter referred to as "conventional products"), cutting The cutting performance of the tap was confirmed. The invention 1, invention 2 and conventional products used in this cutting processing test were all cutting The common specifications for the taps were a nominal diameter of M6 and a pitch P of 1.0 mm. The root diameter (D1) of invention products 1 and 2 was 5.050 mm (thread height h: 0.475 mm), while the root diameter (D1) of the conventional product was 4.684 mm (thread height h: 0.658 mm). Furthermore, the cutting edges of the second and subsequent threads in the complete thread portion of invention product 2 were provided with the following cutting edges as shown in Figures 10 to 12. cutting The tap was subjected to the same chamfering process as the tap (fourth embodiment).

[0022] The machining conditions for the cutting test were as follows: ·Work material: Carbon steel (S50C) Pilot hole diameter: 5.0mm ·Cutting speed: 30.0(m / min) Rotation speed: 1592 (l / min) Feed rate: 1592 (mm / min) Effective screw length: 2D (12mm) Cutting fluid: Water-soluble cutting fluid ·Machine used: Vertical MC

[0023] The cutting test started under the above-mentioned conditions. cutting The cutting process was continued until a cutting abnormality was confirmed, such as chipping of the cutting edge of the tap or a sudden increase in the cutting noise of the workpiece. After these phenomena were confirmed, the test was stopped and the condition of the workpiece and each of the cutting conditions were confirmed. cutting The surface condition of the tap was observed.

[0024] In this cutting test, an abnormal sound was confirmed when the cumulative number of holes machined from the start of the test using the conventional product reached 1,200, so the cutting test using invention product 1 and invention product 2 was also completed at that point. After the test was completed, the internal condition of the workpiece at that point and the cutting The condition of the cutting edge of the tap was confirmed. Figure 11 shows the condition of the threads on the workpiece cut by Invention Product 1 after the cutting test was completed (when the cumulative number of holes machined reached 1,200), and Figure 12 shows the condition of the threads on the workpiece cut by the conventional product. Note that each of the images shown in Figures 11 and 12 is an image of the workpiece cut in the depth direction of the screw hole after the cutting test was completed, and the ridge of a specific thread was scanned with a three-dimensional measuring machine.

[0025] First, the condition of the threads (ridges) machined using Invention Product 1 was measured, and no burrs or burrs were found on the threads, as shown in Figure 11. On the other hand, the condition of the threads machined using the conventional product was confirmed to have burrs approximately 24 μm high on the threads, as shown in Figure 12. This is presumably because the relationship between the nominal diameter (D0), root diameter (D1), pitch (P), and thread height (h) of Invention Product 1 satisfies the relationships in formulas (1) and (2) described above; in other words, it is the effect of having a larger root diameter compared to the conventional product.

[0026] Next, when the cutting edge condition of the products of the present invention was observed after the cutting test, no chipping of the cutting edge was confirmed in product 2. In contrast, chipping (loss of the cutting edge) was confirmed on part of the cutting edge at the full crest portion of the conventional product and product 1. This is presumably due to the fact that the specifications of product 2 satisfy the relationship between formulas (1) and (2) described above, and also due to the effect of chamfering the cutting edge at the full crest portion (especially from the second crest onwards). [Industrial Applicability]

[0027] The present invention cutting The tap can prevent chipping of the cutting edge at the full ridge even when cutting is performed over the entire chamfer. cutting Excellent tapping accuracy. This allows various cutting Available for tapping. [Explanation of symbols]

[0028] 10,310 Biting part 11,12 Chamfer thread 13,14 Valley 20,320 Complete mountain section 21, 22, 23 Full thread 24,25 Valley 31~33,331~333 Groove (Twisted Groove) 41~43,341~343 Chamfered section 51~53,351~353 cutting edge 90 shank 100, 200, 300, 400 cutting Tap D0 cutting Tap nominal diameter D1 Diameter of the bottom of the valley (valley diameter) O1, O2 cutting Tap rotation axis P Thread pitch h Thread height

Claims

1. at least, a chamfer having a plurality of threads for threading a workpiece and for cutting the workpiece; a complete ridge portion having a cutting edge formed continuously from the chamfer portion; a groove portion provided on the chamfer portion and the complete crest portion for discharging chips of the workpiece cut by the chamfer portion; A cutting tap having In the relationship between the nominal diameter D0, the root diameter D1, the pitch P, and the height h of the thread of the cutting tap, The following formulas (1) and (2) are satisfied simultaneously: D1≧D0-P...(1) h≦P / 2 (2) A cutting tap characterized by:

2. 2. The cutting tap according to claim 1, wherein the cutting edge of the full crest portion is chamfered.

3. 3. The cutting tap according to claim 2, wherein the chamfering is performed on the second and subsequent threads of the complete thread portion.

4. 4. The cutting tap according to claim 2, wherein the chamfering is performed on all or part of the cutting edge of the complete crest portion except for the root of the complete crest portion.

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