JPS58143918A - Small-diameter tap - Google Patents

Abstract

PURPOSE:To enhance the durability of a small-diameter tap for releasing cut material by making the cutting height of the bottom of thread larger than that of ordinary taps in the profile of the thread while the angle of the chamferring gradient is made smaller in the chamfer section. CONSTITUTION:In the profile of the thread of small-diameter tap 6 for releasing cut material, the cutting height of the bottom of the thread is set at a larger value of 4/9H to H/4 (H=the height of the range) as compared with that of the conventional tap while the tip diameter d2 of the chamfer is made to match the bottom of the thread. This reduces the angle of the chamferring gradient of the chamfer section 16. Thus, a range of the thread somewhere in the length 16 of the chamfer works so effectively to produce the durability of a tap.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a small-diameter tap particularly for use with difficult-to-cut materials, and the present invention relates to an improvement in a small-diameter tap for use with difficult-to-cut materials. In addition, by matching the chamfered tip diameter to the root of the valley, the chamfer slope angle of the chamfered part is reduced, increasing the iron loss strength of the thread and the breakage strength of the tap, increasing cutting durability. .

Conventionally, taps for difficult-to-cut materials are based on general-use standard taps, but the material, heat treatment method (including surface treatment method), or shape has been modified to improve the tap's wear resistance and extend its durable life. ? The prerequisite is to obtain the female thread grade specified by JIS, etc., or to take measures to prevent screw loosening and increase the shear stress of the female thread within the allowable value range. ＼The ratio was increased, and no particular modification was made to the thread of the tap.

Therefore, when tapping a material with extremely poor machinability with a small-diameter tap, the first thing you will notice is the chamfered cutting edge (
The wear of 1) begins and progresses, and then among the parallel thread parts (2) that are not subjected to cutting loads, threads with a high concentration of repeated fatigue due to elastic displacement generated from twisting and returning of the tap due to cutting A crack started from the bottom of the mountain (3) and grew to the bottom of the next valley, causing the thread to pierce.

As the sharpness of the chamfered cutting edge portion (1) further deteriorated, the cutting torque reached the destructive torque of the tap, resulting in torsional failure starting from the thread root, and the tap broke. When a tap breaks, there is no effective method for removing the broken tap from inside the workpiece material in the case of small-diameter taps, and the workpiece is usually rendered unusable.

The present invention takes a step away from the conventional concept by focusing on increasing the height of the root cutout 4) in order to strengthen the weak points of conventional taps in FIG. By setting the maximum dimension within the range that maintains all the characteristics of the screw, the stress concentration at the root of a specific screw that occurs due to elastic displacement due to the ramming action is completely relaxed, and the timing of iron loss and breakage of the tapped screw thread is extended. This was an attempt to dramatically increase the durability of the tap.

It has been clarified through fatigue tests that increasing the height 4) of the root cut of a male thread such as a bolt increases the breaking strength of the male thread, and JIS B 0.203 shown in Figure 3 above has shown that the breaking strength of the male thread increases. For metric coarse screws, the height of the root cut is 4) k - (H = height of the peak), and the main purpose is for aircraft screw parts that require a very high fatigue life. AJ79 Cne I
:, I) Abbreviation: UNJ) It is also known that the height of the valley bottom cutout is 41:iH to alleviate stress.

In small-diameter taps, this stress concentration is noticeable in nickel-based alloy steels such as titanium alloys, stainless steel, and heat-resistant steel, which have particularly poor machinability.To tap small-diameter screws into these materials with poor machinability, h (hitting rate) in Figure 3 mentioned in "JT, s B O10/screw terminology"
The prepared hole diameter (5) in Fig.
The diameter of the drill hole) D is often used.

This is the only measure that can be taken on the female thread side to obtain a female thread in the workpiece material. In the figure, (6) indicates a tap, and (7) indicates a female thread.

Above JTS B 020! ;For metric coarse threads,
(8) in Fig. 3 is the inner diameter reference dimension, and the hit ratio is 100%, so when the effective diameter reference dimension is the prepared hole diameter, the height 9) is as follows: Hitsuka＼Rate Otsuo
%, and therefore, if the rate is 0%, it can be said that the pilot hole diameter is even larger than the effective diameter reference dimension.

For example, in the case of a metric coarse thread, using a tap sound with a root cut height of - will reduce the cutting resistance to the tap due to the effect of the pilot hole diameter. However, by increasing the height of the thread root cutout of the tap within a range that does not affect the overall pilot hole diameter, and by matching the chamfered tip diameter to this root, the strength of the tap can be increased, and the thread of the chamfered portion of the tap can be increased. This synergistic effect can further improve the tough screw tapping operation.

The height of the thread root cut of the tap of the present invention is in the range of 00 and 01) in Fig. 5, and the numerical value is the height of the root cut when ao @ the height of the root cut when total 7 aυ. The diameter is O"TH, which is larger than the JIS metric thread 1MIL S-Z179 -H (see Table 14)0 Table 1 The remaining seven points of the present invention are The chamfered tip diameter (dl) of the tap with the height of the valley bottom cut and the chamfered slope surface Q51 are naturally located at the starting point of 04 in Fig. 4 in order to fully demonstrate the action and effect of the chamfered part. It is to set it to .

Therefore, if the chamfer length is the same as the conventional tap, the chamfer tip diameter of the conventional tap is [d2], and the chamfer slope surface is 0.
7) Therefore, with respect to the diameter of the prepared hole targeted by the present invention, the screw thread that performs the cutting action is located at the prepared hole diameter position α as shown in (G).
It can be seen that only the top part of the thread acts from the cutting action, and the thread below the Q position does not perform any cutting action, so the life of the tap is extremely shortened.

In the present invention, such iron black is removed and the thread between the chamfer length α0 acts effectively for cutting, so the entire cutting mechanism is fully utilized compared to conventional taps, so the wear resistance of the chamfered part is improved. It is clear that a tap with increased force and durability is obtained.

The present invention is a defective tap with multiple improved parts as described above.

[Brief explanation of the drawing]

Figure 1 is a shape diagram of a conventional small-diameter tap, Figure 2 is a partial view of the thread of a conventional small-diameter tap, and Figure 3 is a JISB 020! ;
The standard thread shape for metric coarse threads, Figure 1 shows the relationship between the pilot hole diameter for female threads with a tightening rate of about 50% and the threads of conventional taps, and Figure S shows the tap of the present invention. The shape of the thread, Figure 3 is a chamfered part of the tap, and is a comparison diagram of the differences between the present invention and a conventional tap. 0, α4...height of the cut at the bottom of the thread αQ...
Negative angled slope surface (dl)...Diameter of chamfered tip 101- Procedural amendment-letter (spontaneous), -September 2, 1919, Patent Office Examiner, Commissioner of the Patent Office, 1, Display of case Showa 1957 Patent Application No. 2'1g1l No. 2, Name of the invention Pathway Tap 3, Relationship with the case of the person making the amendment Patent applicant's name OnisG Co., Ltd. (name) 4, Agent address Higashi-ku, Higashi-ku, Nagoya City 18 Katahata-cho (5173) Patent attorney 13's residence / <052
>962-7601 (representative), 971-93355,
Date of notice of reasons for refusal Showa year month
Day 6, number of inventions increased by amendment 7, subject of amendment Brief description of drawings in the specification column 103
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Claims (1)

[Claims] Has a screw thread with a height of the thread root cut in the range of i7H to T (H: height of the pointed crest), and a chamfered tip diameter? A small diameter tap that matches the position of the valley bottom.