JPH0639012B2 - Tap for nuts - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a nut tap used when tapping a nut with a nut tapping machine (automatic nut tapping machine).

[Conventional technology and its problems]

In order to form a highly accurate screw using a nut tap or a bend tap or other nut tap, it goes without saying that a nut tap with high screw accuracy is used, but the bite of the tap with respect to the prepared hole of the nut It is necessary to make sure to bite.

By the way, in the nut tap, as shown in FIG. 7, usually, there is a relief in the radial direction in the biting portion 30 and the gradient in the axial direction is gentle, and moreover, the flank 32 of the screw thread 31 of the biting portion 30 is used. There is an escape. When such a nut tap is used, for example, when tapping is performed by a nut tapping machine disclosed in Japanese Utility Model Publication No. 49-45029, the biting portion 30 does not surely bite the inner surface of the prepared hole of the nut, and The pushing force of the push rod that pushes toward the tap causes the nut to advance too far from the tap pitch,
Like the nut 33 shown in the figure, the thread 3 at the beginning of biting
A collapsed portion 35 is generated at 4. In addition, since the biting portion 30 has a gradual slope, the outer diameter surface of the biting portion performs a reamer action until the tap completely bites the nut, which causes an inconvenience of expanding the prepared hole of the nut.

In order to eliminate such inconvenience, it is sufficient to use a nut tap that does not escape in the flank of the screw thread in the bite part, but in this case, since the flank of the screw thread makes full contact with the cutting groove, seizure, welding However, such problems occur, making high-speed tapping difficult.

[Object of the Invention]

Therefore, an object of the present invention is to solve the above-mentioned conventional inconvenience, improve the bite to the nut, and provide a nut tap capable of accurately cutting the thread at the beginning of the bite of the nut. .

[Structure of Invention]

In order to achieve the above object, in the first invention,
On the outer circumference of each thread provided on the tapered bite part,
Two chamfered flanks, which are taken along the lead of the screw thread and have a step in the radial direction, are provided so that the chamfered flank on the lower step side is located at the front side of the advance side of the tap. The flank angle of the rising surface, which is formed between the flanks and extends along the lead of the screw thread, is 0 ° or less.

Further, in the second invention, a second biting flank is formed along the lead of the thread on the outer periphery of each thread provided in the tapered biting portion, and the biting surface is formed. A groove is provided along the lead of the screw thread, and the French angle of the leading flank of the groove is set to 0 ° or less.

Here, along the lead means that the lead of the screw thread is the same as the lead of the rising surface and the groove, or the lead of the rising surface and the groove is slightly larger than the lead of the screw thread, including so-called advanceability. .

[Action]

When the nut tap according to the first aspect of the invention is rotated and the nut having the pilot hole in the bite portion is pushed in, the outer diameter edge of the rising surface formed on the thread of the bite portion becomes the inner peripheral surface of the pilot hole. Since the flank surface of the rising surface is 0 ° or less, the reamer action does not occur, and collapse of the thread on the cut side due to excessive advance of the nut is prevented.

Further, when the nut tap according to the second aspect of the invention is rotated and the nut having the pilot hole in the biting portion is pushed in, the outer diameter edge of the advancing flank of the groove formed on the outer periphery of the thread is inside the pilot hole. It bites into the lap, and the flank angle of the leading flank is 0.
Since it is less than 0 °, the reamer action does not occur and the thread on the cut side is prevented from collapsing due to the nut moving too far.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

As shown in FIGS. 1 and 2, the nut tap 1 is provided with a chamfered portion 3 having a gentle slope at the tip of a complete thread portion 2 as in the conventional nut tap. A plurality of threads 4 are provided on the outer circumference of 3. Similar to the conventional nut tap, the thread 4 has a height gradually increasing from the thread at the tip of the biting portion 3 to the thread at the rear end, and the flank of each thread 4 on the advance side is increased. 5 and trailing flank 6 are provided with a clearance angle of about 30 '.

On the outer periphery of the thread 4 in the chamfered portion 3, two chamfered flanks 7a and 7b having a step in the radial direction, and the chamfered flank 7a on the lower step side are located at the front of the tap advance side. Is provided. Each flank 7a, 7b
Is taken along the lead of the screw thread 4, and the clearance angle is about 2 ° to 10 °.

The rising surface 8 between the low flank flank 7a and the high flank flank 7b is along the lead of the screw thread 4, and the flank angle of the rising face 8 is 0 ° or less. .

Here, the flank angle of the rising surface 8 refers to an angle formed by each straight line measured in a sectional shape including the tap axis of the rising surface 8 and a straight line perpendicular to the axis of the tap, and the flank angle is 0 °. The following includes a state in which each measured straight line coincides with a straight line orthogonal to the axis of the tap, and a state in which the plane perpendicular to the tapered surface of the biting portion has a slope toward the saw from that state.

To form the nut tap as described above, as shown in FIG. 2, the axis of the grindstone 20 is arranged so that the rotation axis 21 of the circular grindstone 20 and the outer peripheral surface of the biting portion 3 of the tap 1 are parallel to each other. With the shaft 9 of the tap 1 tilted with respect to the core 21, the grindstone 20 and the tap 1 are rotated in opposite directions to each other.
0 is moved along the lead of tap 1, and the grindstone 20
Alternatively, a grinding method of moving either one of the taps 1 in the radial direction can be adopted.

As described above, since the rising surface 8 having a flank angle of 0 ° or less is formed along the lead of the thread 4 on the outer periphery of the thread 4 of the biting section 3, the biting section 3 of the tap 1 is formed. When the nut having the prepared hole is pushed toward the outer surface, the outer diameter edge 10 of the rising surface 8 surely bites the inner surface of the prepared hole of the nut to prevent the nut from moving in the axial direction. Therefore, when a screw thread is formed on the inner diameter surface of the nut by the rotation of the tap 1 and the axial pushing of the nut, the screw thread at the beginning of the bite of the nut does not collapse, and at the bite portion 3 of the tap 1. The complete thread 2 of the tap 1 is guided and moved in the formed thread groove, and as a result, a nut with a high screw precision can be formed.

3 and 5 show another embodiment of the nut tap according to the present invention. Nut tap 1 shown in FIG.
Is formed on the outer periphery of the thread 4 of the chamfered portion 3 by forming three chamfered flanks 7a, 7b, 7c in which the advancing side end and the trailing side end of the screw thread 4 are lowered. Part flank 7a and the higher flank flank 7 following it
A rising surface 8 is provided along the lead of the screw thread 4 between b. Like the rising surface 8 shown in FIG. 1, the rising surface 8 has a flank angle of 0 ° or less.

When forming the tap as described above, as shown in FIG. 4, a circular grindstone 20 having a width dimension of the outer diameter surface of the grindstone 20 extending between the adjacent screw threads 4 of the chamfered portion 3 is used. Using, the outer peripheral surface of the chamfered portion 3 of the tap 1 is parallel to the rotation axis of the grindstone 20, and the grindstone 20 is moved along the lead of the chamfered portion 3 while the tap 1 and the grindstone 20 are rotated in opposite directions. In addition, a grinding method in which either one of the grindstone 20 and the tap 1 is moved in the radial direction can be adopted.

In addition, the nut tap 1 shown in FIG. 5 has a chamfered flank 11 formed second along the lead on the outer periphery of the screw thread 4 of the chamfered portion 3, and the chamfered flank 11 has a thread The groove 12 is provided along the lead No. 4 and the flank angle of the leading flank 13 of the groove 12 is set to 0 ° or less.

When forming the tap as described above, as shown in FIG. 6, the outer peripheral surface of the circular grindstone 20 is a tapered surface 22, and the outer peripheral portion of the large end surface of the grindstone 20 is a tapered surface 23. The grindstone 20 and the tap 1 are rotated in the opposite directions orthogonal to the outer peripheral surface of the bite part 3 of the tap 1, the grindstone 20 is moved along the lead of the screw thread 4 of the bite part 3, and the grindstone 20 or the tap. It is possible to employ a grinding method in which one of the two is moved in the radial direction.

In each of the above embodiments, the rising surface 8 and the groove 12 are formed.
Since the flank angle of the flank 13 on the leading side is less than 0 °, the rising surface 8 and the outer diameter edge 10 of the flank 13 are
It is possible to surely eat the inner periphery of the prepared hole of the nut, and it is possible to surely prevent the nut from excessively advancing in the initial stage of cutting.

The rising surface 8 and the flank 13 may be formed only on the screw thread 4 at the tip of the biting portion 3.

〔The invention's effect〕

As described above, in the nut tap according to the present invention, a rising surface or groove is formed along the lead of the thread on the outer periphery of the thread of the biting portion, and the rising surface and the flank of the groove flank of the groove are formed. Since the angle is set to 0 ° or less, it is possible to reliably bite the rising surface and the outer diameter edge of the advancing flank on the inner peripheral surface of the prepared hole of the nut when forming the thread on the nut.

Therefore, it is possible to prevent the nut from advancing too far beyond the lead of the thread at the biting part of the tap, prevent the thread from collapsing at the beginning of the nut biting, and form a highly accurate thread. You can

[Brief description of drawings]

1 to 6 show an embodiment of a nut tap according to the present invention, and FIGS. 1, 3 and 5 are perspective views showing a part of a chamfered portion, FIG. 2 and FIG. FIG. 6 and FIG. 6 are partial side views, FIG. 7 is a side view showing a part of a conventional nut tap, and FIG. 8 is a sectional view of a nut formed by the conventional nut tap. 3 ... Biting part, 4 ... Thread, 8 ... Rising surface, 11 ... Groove, 12 ... Groove, 13 ... Leading side flank.

Claims (2)

[Claims] 1. A low step side is provided with two chamfered flanks, which are secondly cut along the lead of the screw thread and have a step in the radial direction on the outer periphery of each screw thread provided in a tapered chamfer. It is characterized in that the chamfered flank face of is located on the front side of the advancing side of the tap, is formed between the two chamfered flank faces, and the flank angle of the rising surface along the lead of the screw thread is 0 ° or less. And taps for nuts. 2. A biting flank formed second along the lead of the thread is formed on the outer periphery of each thread provided on the tapered biting portion, and the thread flank is formed on the flank. A nut tap characterized in that a groove is provided along the lead of and the flank angle of the leading flank of the groove is set to 0 ° or less.