JP3728673B2 - Thread tap - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thread cutting tap, and more particularly, to a tap that can prevent a 'screw fall' phenomenon even when there is excessive pushing in the tap axis direction or pulling by a shank. In the following, for convenience of explanation, a nut tap will be described as an example, but the present invention can be similarly applied to other types of threading taps.
[0002]
[Prior art]
For example, when a nut is manufactured, a female screw is cut by rotating a nut raw material having a prepared hole while pushing a tap.
[0003]
Usually, in such a nut tap, as shown in FIG. 3, a plurality of cutting edges 500... Are formed along a spiral shape, and a plurality of complete thread-shaped portions 510. 4 is formed, and each cutting edge 500 of the biting portion 50 shares a predetermined cutting amount with respect to the pilot hole of the tap raw material 30 as shown in FIG. And cutting is done.
[0004]
The cutting edges 500 of the bite portion 50 are gradually reduced in effective diameter toward the last cutting edge and gradually gradually turned toward the final cutting edge so that the internal thread can be cut with a small torque. It was formed in an incomplete thread shape that would be a mountain shape.
[0005]
[Problems to be solved by the invention]
However, although the conventional nut tap has an advantage that the cutting torque is small due to the structure of the cutting edge 500 of the bite portion 50, the cutting blade 500 is worn due to the small cutting torque. As a result, when the biting becomes worse, the influence of excessive pushing in the direction of the tap axis or pulling by the shank has appeared remarkably with respect to thread cutting. For example, when the influence of tension appears, as shown in FIGS. 5A, 5B and 5C, the cutting edge gradually shifts to the rear side in the axial direction and part of the thread is missing. There was also a so-called reamer phenomenon that caused the so-called 'screw fall' phenomenon and scraped off the top of the thread and the thread itself.
[0006]
When such a screw fall or reamer phenomenon due to a biting failure due to wear of the tap occurs, there has been a problem that the effective diameter becomes too large or the fatal defect becomes too large.
[0007]
In view of such a problem, an object of the present invention is to provide a threading tap that can prevent a screw fall or a reamer phenomenon even if the tap shaft is excessively pushed or pulled by a shank.
[0008]
[Means for Solving the Problems]
Accordingly, the threading tap according to the present invention includes a biting portion in which a plurality of incomplete thread-shaped cutting edges are formed at a predetermined equal pitch and along a spiral shape, and a plurality of complete thread-shaped shapes behind the biting portion. The part is composed of a complete thread part formed at a predetermined equal pitch and along a spiral shape, and a plurality of cutting edges of the biting part cut a female thread into a predetermined cut by pushing and rotating into the prepared material prepared hole In a thread tap designed to cut by an amount, a biting lead portion having at least one cutting edge along a spiral shape is formed at a predetermined equal pitch position in front of the biting portion, and the biting lead The cutting edge of the part is smaller than the effective diameter of the cutting edge of the biting part.
[0009]
A feature of the present invention is that a plurality of successive biting portions are formed by forming a lead groove by a cutting blade of a biting lead portion whose blade width is smaller than the effective diameter of the biting portion cutting blade and fitting the spiral shape portion of the cutting blade. The point is to position the cutting edge. Therefore, at least one cutting edge of the biting lead portion is sufficient, but two or three are optimal in consideration of manufacturing and leadability. The cutting edge of the biting lead portion is preferably a complete thread shape.
[0010]
The blade width of the cutting edge of the biting lead portion (width of the blade base) is preferably smaller than ½ of the blade width of the cutting edge of the biting portion (width of the blade base). The reason for this is that, as a result of various experiments, even if there is excessive pushing or tension in the tap axis direction and the cutting edge of the biting lead portion is displaced in the axial direction, the blade width is 1 of the biting width of the biting portion. This is because it has been confirmed that if it is smaller than / 2, the deviation is contained in the portion cut by the cutting edge of the chamfered portion and does not adversely affect the final screw shape.
[0011]
Further, the height of the cutting edge of the biting lead part is desirably larger than 0.3 mm. The reason for this is that, as a result of various experiments, it was found that when the height of the cutting edge is less than 0.3 mm, the chamfered lead portion is liable to shift with respect to excessive axial pushing or pulling.
[0012]
The effective diameter of the cutting edge of the bite portion may be decreased toward the final cutting edge as in the case of the conventional threading tap, or may be increased toward the final cutting edge. However, since the cutting torque increases when the effective diameter is increased toward the final cutting edge, it is preferably applied to a tap for thread cutting that is reduced toward the conventional final cutting edge.
[0013]
[Operation and effect of the invention]
Since the chamfered lead portion smaller than the effective diameter of the chamfered cutting edge is formed in front of the chamfered portion, when the lead groove is cut by the chamfered lead portion, the spiral of the cutting edge The shape part firmly bites into the lead groove, and the first cutting edge of the biting part is accurately positioned to perform cutting, and thus the plurality of cutting edges of the following biting part are cut into the cutting edge of the biting lead part. And the complete thread is cut while being positioned one after another by the helically shaped part.
[0014]
Further, when the height of the cutting edge of the biting lead portion is larger than 0.3 mm, the deviation of the biting lead portion can be reduced with respect to excessive pressing or pulling in the axial direction. In addition, if the cutting edge width of the chamfered lead part is made smaller than 1/2 of the width of the chamfered cutting edge, even if the chamfered lead part is displaced due to excessive pressing or pulling in the tap axis direction, the deviation is eroded. It fits in the part to be cut with the cutting edge of the attached part.
[0015]
Therefore, according to the present invention, since the front chamfered lead part becomes the lead of the cutting edge of the following chamfered part, even if the tap shaft direction is excessively pushed or pulled by the shank, there is almost no influence on the thread cutting. The screw 'fall down' and 'reamer' phenomenon can be surely prevented. As a result, for example, highly accurate axial force management can be performed with the tightening torque of the nut. In particular, if the blade width of the cutting edge of the biting lead is smaller than 1/2 of the width of the biting cutting edge, excessive press in the tap axis direction or excessive pulling by the shank will occur in the initial stage and the biting lead will shift. Even if this occurs, it is repaired with the following bite portion and complete thread portion, so that the designed screw can be formed accurately.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on specific examples shown in the drawings. FIG. 1 shows a first embodiment of the present invention. In the figure, the nut tap 10 has a biting portion 50 on the front end side, a complete screw portion 51 formed on the rear side thereof, and a mounting screw portion 52 formed on the rear end portion. A plurality of cutting edges 500... Are formed on the biting portion 50 at a predetermined equal pitch and along a spiral shape, and a plurality of complete thread-shaped portions 510. It is formed along the pitch and along the spiral shape.
[0017]
Each cutting edge 500 of the bite portion 50 has an effective diameter that decreases along the spiral shape of the cutting edge toward the rear final cutting edge 500, and gradually becomes a complete thread shape toward the final cutting edge 500. In general, the complete thread portion 51 of the complete screw portion 51 has an effective diameter smaller than the effective diameter of the final cutting edge 500 of the bite portion 50.
[0018]
A chamfered lead portion 11 is formed in front of the chamfered portion 50, and the chamfered lead portion 11 has two cutting edges (110, 110) along a spiral shape at predetermined equal pitch positions. The blades (110, 110) have the same effective diameter along the spiral shape, and the effective diameter is smaller than the effective diameter of the cutting edge (500 ...) of the biting portion (50), and the width of the blade base (L) Is smaller than 1/2 of the width (L1) of the blade base of the cutting edge (500) of the biting portion (50), and the height (H) of the cutting edge (110) of the biting lead portion (11) Is formed larger than 0.3 mm.
[0019]
When cutting a female thread into the nut base material 30, the nut tap 10 of this example is pushed into the prepared hole of the nut base material 30 while rotating. Then, as shown in FIG. 2, the first cutting edge 110 of the biting lead portion 11 cuts the lead groove 40 having the cross-sectional shape into the pilot hole of the nut shaped member 30.
[0020]
Then, the two cutting edges 110 and 110 of the biting lead portion 11 and the spiral-shaped portions 111 and 111 thereof serve as leads to guide and accurately position the first cutting edge 500 of the biting portion 50 that follows. The groove 31 is cut. Similarly, the next cutting edge 500 is also accurately positioned by the two cutting edges 110 and 110 of the biting lead portion 11 and the spiral-shaped portions 111 and 111 to cut the thread groove 32. Thereafter, the biting edge 500 is bitten similarly. Each of the cutting edges 500... Of the portion 50 performs cutting accurately while being guided by the two cutting edges 110 and 110 of the biting lead portion 11 and the spiral-shaped portions 111 and 111 thereof.
[0021]
On the other hand, when there is excessive pushing in the direction of the tap axis or pulling of the shank, with conventional taps there is a concern about the 'screw fall' phenomenon or 'reamer phenomenon' due to poor biting due to wear of the tap as described above. In the nut tap 10 of the example, the lead groove 40 is first formed by the biting lead portion 11, and the two cutting blades 110, 110 of the biting lead portion 11 and the spiral-shaped portions 111, 111 are bitten by this. Since the cutting blades 500... Of the portion 50 are positioned accurately and cut one after another, a thread having a predetermined shape is accurately cut as a whole.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention.
FIG. 2 is a view for explaining the cutting action of the first embodiment.
FIG. 3 is a schematic configuration diagram showing a conventional nut tap.
FIG. 4 is a diagram for explaining the cutting action when the pressing with respect to the rotation of the tap is accurate.
FIG. 5 is a diagram for explaining a cutting action when a shank is pulled.
[Explanation of symbols]
10 Nut Tap 11 Chamfered Lead Part 110 Cutting Edge 111 Spiral Shaped Part 50 Chamfered Part 500 Cutting Edge 51 Fully Threaded Part 510 Fully Threaded Part

Claims (3)

A chamfered portion in which a plurality of incomplete thread-shaped cutting edges are formed at a predetermined equal pitch and along a spiral shape, and a plurality of complete thread-shaped portions at a predetermined pitch and a spiral shape behind the biting portion. Thread taps that consist of a complete thread part formed along the edge, and in which each of the cutting edges of the biting part cuts the female thread by a predetermined depth by being pushed into and rotated into the shaped material pilot hole In
A chamfered lead portion (11) having at least one cutting edge (110) along a spiral shape is formed in front of the chamfered portion (50) at a predetermined equal pitch, and the chamfered lead portion (11) A threading tap characterized in that the cutting edge (110) is formed into a complete thread shape smaller than the effective diameter of the cutting edge (500 ...) of the biting portion (50).   The cutting edge (110) of the biting lead part (11) has an effective diameter smaller than the effective diameter of the cutting edge (500 ...) of the biting part (50), and its width (L) is the biting part. The threading tap according to claim 1, wherein the threading tap is narrower than a half of the width (L1) of the cutting edge (500) of (50).   The threading tap according to claim 1 or 2, wherein the cutting edge (110) of the biting lead portion (11) has a height (H) larger than 0.3 mm.

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