JP2549711Y2 - Taps for blind hole cutting - Google Patents

Description

[Detailed description of the invention]

[0001]

INVENTION The present invention relates to a relates to a tap, the more detail, for example, stops which can be suitably cutting a hole or the like blind against hard materials such as carbon steel hole cutting pressure
Related to taps for construction .

[0002]

2. Description of the Related Art Conventionally, a carbide tap has been used to form a female screw on the inner wall surface of a prepared hole drilled by a drill or the like. As shown in FIG.
Is composed of a screw portion 4 and a shank portion 6, and the screw portion 4 includes a biting portion 8 and a complete screw portion 10. Four cutting edges 12a to 12d are formed on the screw portion 4 so as to be deviated from each other by 90 ° with respect to the axis, and each of the cutting edges 12a to 12d is formed.
Relief grooves 14a to 14d for discharging cutting chips are defined between d. In this case, the carbide tap 2 generally has an inclination angle A of the biting portion 8 with respect to the axis of 18 to 23 degrees.
°, the tapping blade length B is about 35 mm, and the number of threads of the complete threaded portion 10 is as large as about 20. Tapping is performed while jetting cutting oil to the machining site.

[0003]

However, as the size of the workpiece increases, the diameter of the hole to be machined by the tap tends to increase. When tapping is performed on the hole having the enlarged diameter by using the carbide tap 2, poor accuracy of the dimensions of the thread formed on the workpiece occurs, and the finished surface becomes defective. The inconvenience that the carbide tap 2 is damaged and the life is shortened has become apparent.

[0004] Therefore, according to what the applicant considers, the above-mentioned inconvenience is caused, for example, when forming a blind hole, the escape grooves 14a to 14d defined between the cutting blades 12a to 12d.
The cutting chips are not sufficiently discharged to the outside from the
It has been found that the tapped threads are crushed by the cutting chips remaining in a to 14d. In addition, for example, when tapping is performed on a medium-high carbon steel-based hard material, the generated cutting chips are hard, and the thread diameter increases as the hole diameter increases (for example, 15 mm or more). In addition, since cutting chips become large, the cutting chips tend to remain in the escape grooves 14a to 14d. As a result, the remaining cutting chips enter between the cutting blades 12a to 12d and the workpiece, and damage the already tapped threads.
Poor precision and finished surface. Further, the cutting blades 12a to 12d may be damaged by the cutting chips.

[0005] The present invention is, was made in order to overcome the disadvantages, without damaging the thread by the cutting chips generated during machining, Thomas dimensional accuracy good
It is an object of the present invention to provide a blind hole cutting tap capable of performing tapping of a drilled hole and achieving long life.

[0006]

To SUMMARY OF THE INVENTION To achieve the above object, the present invention may possess a complete thread portion which is <br/> formed by concatenating the diet with portion and engageable portion of the tip , Blind hole in the machined part
In the tap for cutting, the number of the threads of the complete screw portion is set to 3 to 6 and the inclination of the biting portion with respect to the axis of the tap.
The angle is formed at 12 ° to 15 °, and the biting portion is formed.
Is inclined more axially than the biting portion, and the biting portion is tilted.
The amount of food drop formed at the tip of
Is set .

[0007]

[Effect] In the blind hole tapping tap according to the present invention,
The number of threads of the complete thread portion is set to three to six. Therefore, the number of threads of the completely threaded portion is reduced as compared with the conventional case. As a result, cutting chips generated by tapping enter between the cutting edge and the workpiece formed by the small thread of the complete thread portion and remain in the escape groove defined between the cutting edges. Without being discharged through the escape groove, it is preferably discharged to the outside.

Further, while the inclination angle of the engageable portion with respect to the axis of the blind hole for cutting tap 12 ° to 15 °, the tip end of the food mounting portion is inclined to the axis side of the diet with portions By setting the amount of the second bite of the bite to 65 μm to 90 μm, it is possible to prevent shaft runout during tapping and to continue stable tapping.

[0009] In addition, the above-mentioned food dropout amount is less than 65 μm.
In some cases, the initial biteability of the inner hole of the pilot hole is poor,
If the additional drop amount exceeds 90 μm, the rotary feed of the tap, etc.
It becomes unstable and causes a reduction in machining accuracy.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A blind hole cutting tap according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1A is a front view showing a tap according to an embodiment of the present invention, FIG. 1B is a right side view of FIG. 1A, and FIG. 2 is a partially enlarged view of FIG. 1A.

The tap 20 according to the embodiment of the present invention basically includes a screw portion 22 and a shank portion 24. The screw portion 22 includes a biting portion 26 and a completely threaded portion 28. The outer diameter of the completely threaded portion 28 is 16 mm, and the effective diameter is 15 mm. The screw portion 22 has four cutting blades 30 which are deviated by about 90 ° from each other with respect to the axis of the tap 20 and are used for preparing a pre-drilled hole for tapping the work.
a to 30d are respectively formed along the axial direction. 1A and 2, the number of threads of the complete screw portion 28 is four. Escape grooves 32a to 32d are formed between the adjacent cutting blades 30a to 30d so as to extend a predetermined length along the axis of the screw portion 22. The shank portion 24 has a flat portion 34 for connecting and holding the tap 20 to a rotary drive source (not shown). The eating part 2
6 is formed in a tapered shape inclined at a predetermined angle with respect to the axis of the tap 20. At this time, the inclination angle C with respect to the axis of the biting portion 26 is formed at 12 ° to 15 °, and an end portion 29 having a larger inclination angle than the inclination angle C is provided at the tip of the biting portion 26. The biting amount D, which is the width of the end portion 29 with respect to the axis, is set to 65 μm to 90 μm (see FIG. 2).

Also, the cutting blades 30a to 3 in the biting portion 26
The number of ridges of 0d is 2.5 and the cutting edge 3 in the completely threaded portion 28
The number of peaks 0a to 30d is 3 to 6 peaks.

The tap 20 according to the present embodiment is basically configured as described above. Next, the operation and effect thereof will be described.

Here, as shown in FIG. 3, a crankshaft 36 is used as a work,
An example of tapping the center screw hole of No. 6 will be described. The crankshaft 36 is attached to the mounting jig 3
The two end portions are held via centering members 40 and 41 mounted on 8. One centering member 40 is provided with a clamp member 42 that engages with the end of the crankshaft 36. In this case, the crankshaft 36
A stepped hole portion 44 that has been pre-drilled by a drilling means such as a drill is formed in advance at the end (see FIG. 4). It should be noted that a portion of the clamp member 42 and the centering member 40 that holds the end of the crankshaft 36 includes:
A through hole 46 for inserting the tap 20 is defined.

First, the flat portion 34 of the shank portion 24 of the tap 20 is connected to a rotary drive source (not shown) via a chuck or the like, and the centering member 40 and the clamp are rotated while rotating the tap 20 under the action of the rotary drive source. Member 4
It is inserted into the stepped hole portion 44 through the second through hole 46. In this case, as shown in FIG. 5, the end portion 29 of the biting portion 26 slides on the step portion of the stepped hole portion 44 and the tap 20 is moved to the stepped hole portion 44.
Then, the cutting blades 30 a to 30 d of the biting portion 26 formed at the tip of the tap 20 start tapping the inner wall surface of the stepped hole portion 44.
In addition, the inclination angle C of the biting portion 26 with respect to the axis of the tap 20 according to the present embodiment is set to 12 ° to 15 °, and about 1
8 [deg.] To 23 [deg.], And the amount D of second bite formed at the tip of the biting portion 26 is 65 [mu] m or more.
By setting the thickness to 90 μm, it is possible to maintain good biting properties at the tip of the biting portion 26 and to prevent the tap 20 from oscillating at the time of tapping. In this case, the Ri inclination angle C is poor is engageable with is less than 12 ° of the engageable portion 26 with respect to the axis of the tap 20, the inclination angle C is inconvenient lacks stability during tapping exceeds 15 ° There is. In addition, the above-mentioned food dropout amount D is 65.
If it is less than μm, the initial biteability of the inner hole of the prepared hole
Inferior, if the second drop D with food exceeds 90 μm, tap 2
Rotation feed of 0 becomes unstable and causes the machining accuracy to decrease.
Cause.

Subsequently, by the self-propelled action, the biting portion 26 is formed.
Cutting edge 30a to 30d, and then the cutting edge 3 of the complete screw portion 28
The burners 0a to 30d slide in contact with the inner wall surface of the stepped hole portion 44 to perform burnishing (see FIG. 6). In this case, since the number of the threads of the complete screw portion 28 is formed as small as four, the cutting chips generated by the cutting blades 30a to 30d generate the escape grooves 32a formed toward the shank portion 24. Through 32d to be discharged to the outside. That is, by setting the number of threads of the complete screw portion 28 to an extremely small number of four threads, the length of the complete screw portion 28 can be reduced as compared with the related art. As a result, the biting portion 26
The amount of cutting chips generated by the cutting blades 30a to 30d is small, so that the cutting chips can be easily discharged to the outside through the escape grooves 32a to 32d without remaining in the escape grooves 32a to 32d.

Further, in the cemented carbide tap 2 according to the prior art, the cutting chips are formed by cutting edges 12a to 12d of the complete screw portion 10.
The tapping thread which has entered between the workpiece and the workpiece damages the tapped thread. However, in the tap 20 according to the present embodiment, by reducing the number of threads of the completely threaded portion 28, cutting chips can be completely threaded. It is possible to prevent the tapped threads from crushing the cutting blades 30a to 30d of the portion 28. Therefore, when the tap 20 according to the present embodiment is used, as shown in FIG. 8B, the thread of the tapped workpiece is formed substantially coincident with the ideal line. On the other hand, when the carbide tap 2 according to the prior art is used, as shown in FIG. 8A, the side surface of the tapped thread on the tap advancing direction side is damaged, and There is an inconvenience that a deviation occurs from the line to be used.

Next, FIG. 7 shows the result of an experiment in which the number of peaks of the cutting blades 30a to 30d in the completely threaded portion 28 of the tap 20 according to the present embodiment is variously changed. In this experiment, a crankshaft 36 was used as a work in the same manner as in the above-described embodiment, and tapping was performed on a center screw hole of the crankshaft 36. As the experimental conditions, 1000 crankshafts 36 were machined according to the number of peaks, and the diameter of a pilot hole formed in the crankshaft 36 in advance was set to 1
An experiment was performed with the range of the number of threads of 4.6 mm and the number of threads in the complete threaded portion 28 being 3 to 8 threads, and it was determined whether or not the thread formed by tapping had a defect in accuracy, a defect in the finished surface, or the like. .

As a result, the number of threads of the complete screw portion 28 is three or more.
In the range of five threads, a thread having good dimensional accuracy could be cut without occurrence of poor thread accuracy or the like. When the number of threads was six, one screw thread was inaccurate, etc., but the degree of damage was extremely small, and the other threads could be cut well. Complete thread 28
When the number of threads was 7 or 8, the poor precision of the threads on the crankshaft 36 gradually increased. Therefore,
When the number of threads of the complete screw portion 28 is in the range of three to six, most preferably three to five, a thread having good dimensional accuracy is formed without damaging the cutting edges 30a to 30d. I was able to.

[0021]

According to the tap for blind hole cutting according to the present invention, the following effects can be obtained.

That is, by setting the number of threads of the completely threaded portion to be three to six, cutting chips generated by tapping are formed between the cutting edge formed by the threads of the completely threaded portion and the workpiece. It is preferably discharged to the outside via the clearance groove without entering the clearance groove and remaining in the clearance groove defined between the cutting blades. Accordingly, the dimensional accuracy without damaging the screw thread formed by the tapping can be processed good thread, because it can avoid damage to the cutting edge formed by the screw thread, blind hole cut
A longer life of the tap for machining can be achieved.

Further, in the conventional tap, a portion of about 2.0 mm from the tip of the cutting edge is cut as a re-grinding portion.
With the blind hole tapping tap according to the present invention, the amount of wear of the cutting edge can be reduced.
You only need to cut the 5mm part, and the cut amount is about 1
It can be suppressed to about / 4 and can be used for a long time.

Further, the inclination angle of the biting portion with respect to the axis of the blind hole cutting tap is set to 12 ° to 15 °, and the tip of the biting portion is tilted more toward the axis than the biting portion. By setting the second bite of the bite formed at the tip of the bite portion to 65 μm to 90 μm, shaft runout during tapping can be prevented and stable blind hole cutting can be continued.

[Brief description of the drawings]

FIG. 1A is a front view of a tap according to an embodiment of the present invention, and FIG. 1B is a right side view of the tap shown in FIG. 1A.

FIG. 2 is a partially enlarged view of a tap shown in FIG. 1A.

FIG. 3 is a front view showing a state where a crankshaft, which is a workpiece to be tapped, is held.

FIG. 4 is a partial cross-sectional view for explaining a state in which tapping is performed on a center screw hole of the crankshaft illustrated in FIG. 3;

FIG. 5 is a partial cross-sectional view for explaining a state in which tapping is performed on a center screw hole of the crankshaft shown in FIG. 3;

FIG. 6 is a partial cross-sectional view for explaining a state in which tapping is performed on a center screw hole of the crankshaft shown in FIG. 3;

FIG. 7 is an explanatory diagram showing a result of an experiment performed using the tap according to the embodiment of the present invention and changing the thread of a completely threaded portion of the tap.

FIG. 8A shows the shape of a thread formed on a workpiece when tapping is performed using a tap according to a conventional example, and FIG. 8B shows tapping using the tap according to the present invention. FIG. 9 is a partial cross-sectional view showing the shape of a thread formed on a work when performing the above.

FIG. 9 is a front view showing a tap according to a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 20 ... Tap 22 ... Screw part 24 ... Shank part 26 ... Biting part 28 ... Completely threaded part 29 ... End part 30a-30d ... Cutting blade 32a-32d
... escape groove 34 ... flat part

Claims (1)

(57) [Scope of request for utility model registration] 1. A possess the complete thread portion and the engageable portion is formed by connecting the food mounting portion of the tip, off the blind hole to be machined portion
In the tap to be machined, the number of threads of the complete thread portion is set to 3 to 6 threads , and the axis of the tap is
The angle of inclination of the biting part with respect to
With the tip of the biting portion closer to the axis than the biting portion.
Inclined and the amount of bite formed at the tip of the bite part
Tomah, characterized in that the set to 65μm~90μm
Tap for drilling holes .