JP3309064B2 - Raising tap with pilot hole and internal thread - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tapping tap for forming a female screw by plastic working for raising a screw thread.

[0002]

2. Description of the Related Art FIG. 6 (a) is a side view showing an example of a conventional tapping tap, and FIG. 6 (b) is a cross-sectional view along a thread of the tapping tap. Usually, the threaded portion 1 has a pointed tip portion 2 which is tapered while having a sharp crest to improve biting into the prepared hole, and is connected to the rear of the bited portion 2. ,
A thread forming portion 3 for forming a female screw having a predetermined size by subjecting the inner wall of the screw hole to plastic working for raising the thread. The cross-sectional shape of the threaded portion 1 is usually polygonal (triangular in the illustrated example) so as to have a plurality of protrusions 4 for controlling the raising action at a plurality of positions in the circumferential direction in order to reduce tapping torque at the time of raising the thread. ).

[0003] Such raised taps are not threaded to non-ferrous alloys such as aluminum alloys and mild steel, which have good spreadability, because chips are not produced because cutting is not performed and the precision of the female screw is stabilized when formed with the tapping. Widely used for.

[0004] However, since the tapping tap forms the female screw by tapping the thread, the degree of the thread tapping greatly differs depending on the dimensional accuracy of the pilot hole, not only the shape and material of the workpiece. As a result, the inner diameter of the female screw greatly changes. For this reason, a considerably strict dimensional tolerance is required for the diameter of the prepared hole in the case of tapping with a raised tap, as compared with the diameter of the prepared hole in the case of tapping with a cutting tap that forms an internal thread by cutting.

[0005] Therefore, when tapping with a tapping tap, the preparation of a screw hole is usually performed by reaming after drilling, which may be cited as a reason for not using the tapping tap. Also, due to the tight dimensional tolerance of the pilot hole diameter, it is generally not possible to use a raised tap without pre-machining for a cast hole.

[0006]

As described above, the use of a tapping tap requires a fairly tight dimensional tolerance in the diameter of a prepared screw hole, and the numerical value is, based on experience, within 5% of the pitch of the female screw to be machined. It has been. For example, when the female screw pitch is 1 mm, the tolerance of the prepared hole diameter becomes an extremely small value of 0.05 mm.

If the screw hole diameter is not appropriate,
If the degree of bulging of the screw thread becomes inappropriate, the following problem occurs. (1) If the pilot hole diameter is too small, the crest of the female screw will rise too high, causing the internal diameter of the female screw to be smaller than the lower limit of the allowable dimension, or the crest of the machined female screw will have If the tapping torque increases at the bottom of the valley, the life of the tapping tap will be shortened, and if the torque increase is excessive,
The breakage tap may be broken. (2) If the diameter of the prepared screw hole is too large, the peak of the female screw is insufficiently raised, and the inner diameter of the female screw becomes larger than the upper limit of the allowable dimension. (3) When the pilot hole is a cast hole, the internal diameter of the internal thread changes in a tapered shape, so that the internal diameter of the female screw also changes in a tapered shape. In some cases, breakage of the raised tap may occur.

On the other hand, when the above-mentioned cutting tap is used, the dimensional tolerance of the pilot hole diameter is equal to the upper and lower limits of the allowable dimension of the inner diameter of the female screw to be machined. This is a considerably large number compared to.

[0009] In order to solve the above-mentioned problems, the present invention provides a forming tap which can be used without problem even with a prepared hole diameter having a dimensional tolerance similar to the prepared hole diameter of a cutting tap. It is an object of the present invention to provide a raised tap that can be used without processing.

[0010]

Means for Solving the Problems and Effects of the Invention To achieve the above object, a tapping tap according to the present invention comprises a biting portion at a tip portion of a screw portion and a threaded portion connected to the biting portion. Cutting at least one groove extending from a front end portion to a rear end portion of the screw portion, and exposing a threaded hole formed on the biting portion using a side wall of the groove. And a female screw for performing a cutting process for exposing the crest of a raised thread formed using at least a portion of the threaded portion immediately after the biting portion using a side wall of the groove. It is characterized by having a blade with an inner diameter.

[0011] In such a raised tap, the biting portion at the tip of the screw portion bites into the prepared screw hole and the tap advances into the depth of the prepared screw hole. The thread of the pilot hole of the screw is used to cut the pilot hole to finish the pilot hole to a predetermined inner diameter, and then the threaded part, especially the first thread, is the pilot hole of the predetermined inner diameter. The female thread is formed by raising the thread to form a female screw, and the female screw inner diameter flattering blade of the threaded portion performs a cutting process to expose the crest of the raised screw thread to make the internal diameter of the female screw a predetermined size. Then, at least one groove extending from the leading end portion to the trailing end portion of the thread portion and used for forming the screw-down hole razor blade and the female screw inner-diameter razor blade has a small amount of a small amount generated by the cutting processing by those blades. Chips are stored in the groove.

Therefore, according to the raised tap of the present invention,
The following remarkable effects are obtained. (1) Even if the screw pilot hole diameter is smaller than the lower limit of the screw pilot hole diameter tolerance when using the conventional tapping tap, the screw pilot hole wiping blade shall wipe the screw pilot hole and finish it to the specified inner diameter. Therefore, the dimensional tolerance of the pilot hole diameter can be expanded more than before for the lower limit side, so that the processing of the pilot hole can be facilitated and the central pilot hole diameter of the dimensional tolerance is smaller than before. It is possible to effectively prevent a female screw inner diameter defect in which the female screw inner diameter dimension becomes excessively large due to insufficient bulging of the screw thread, and the effective diameter of the female screw can be stabilized. (2) Even if the screw hole diameter is small, after the screw tapping blade wipes it down and finishes it to the proper inner diameter, the thread processing section raises the screw thread to form a female thread, so the screw ridge rises Can be reliably prevented, and the life of the forming tap can be shortened due to an increase in tapping torque, and the breakage of the tap can be reliably prevented. (3) As the threaded portion raises the thread to form a female screw, the female screw inner diameter wiping blade of the threaded portion exposes the crest of the raised thread to reduce the internal diameter of the female screw to a predetermined size. Therefore, it is possible to stably obtain the target female screw inner diameter dimension, and by appropriately selecting the shape of the female screw inner diameter wiping blade, the crest of the screw thread has a predetermined round shape or a flat shape as required. It can be processed into a shape. (4) Even when the pilot hole is a cast-out hole with a tapered shape, the threaded part raises the thread and forms a female screw in the pilot hole that has been finished to the appropriate inner diameter by the blade of the pilot hole. Accordingly, the female screw inner diameter flattering blade of the threaded portion exposes the crest of the raised screw thread to make the internal diameter of the female screw a predetermined size, so that the female screw inner diameter without taper can be obtained, and the screw thread can be obtained. Can be reliably prevented from rising excessively, and the life of the raising tap can be shortened and the breakage due to the increase in the tapping torque can be reliably prevented.

[0013] In the tapping tap according to the present invention, preferably, the female screw inner diameter scouring blade is formed at least in a portion of the threaded portion immediately after the biting portion. According to such a configuration, the portion immediately after the bite portion of the thread processing portion, in parallel with raising the thread,
Since the female screw inner diameter flattering blade formed in the above-mentioned portion wipes off the raised screw thread from the first thread, it is ensured that the peak of the machined female screw hits the root of the threaded portion and the tapping torque increases. Can be prevented.

In the tapping tap according to the present invention, the screw portion has three or four circumferential protrusions for controlling the raising action, and the grooves are respectively provided between the adjacent protrusions. It may be provided. According to such a configuration, depending on the circumferential position of the groove,
A female screw inner diameter wiping blade for wiping the crest of the screw thread raised by the projection can be easily formed by using the groove.

In the tapping tap according to the present invention, the groove may extend linearly in parallel with the axis of the tap, or may extend spirally along the axis of the tap. You may do. If the groove is straight, it can be easily processed,
If the groove is formed in a spiral shape, chips can be discharged backward.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Here, FIG. 1 is a side view showing an embodiment of the tapping tap according to the present invention, and FIGS. 2 to 4 are screw threads at II, III and IV parts of the tapping tap of the embodiment shown in FIG. Are cross-sectional views each showing a cross section taken along the line, and the same parts as those in the conventional example are denoted by the same reference numerals.

That is, as shown in FIG. 1, the thread forming tap of this embodiment also has a threaded portion 1 similar to the conventional example shown in FIG.
A biting portion 2 at a tip portion which is tapered and reduced in diameter while having a sharp peak to improve biting into a screw pilot hole;
A threaded portion 3 is formed at the rear of the biting portion 2 and is subjected to plastic working for raising the thread on the inner wall of the prepared screw hole to form a female screw of a predetermined size. As shown in FIGS. 2 to 4 at three cross sections along the axial direction, the screw portion 1 has three protrusions 4 for controlling the raising action at three circumferential positions.

As shown in FIGS. 2 to 4, the tapping tap according to this embodiment further extends straight from the front end to the rear end of the threaded portion 1 in a straight line parallel to the axis of the tap. The groove 5 is disposed between the protrusions 4 adjacent to each other, and the biting portion is formed by using the side walls of the three grooves 5 as shown in FIGS. 2, a raised screw thread formed on the threaded portion 3 by using a screw prepared hole cutting blade 6 for performing a cutting process for removing a screw prepared hole, and the side walls of the three grooves 5. And a female screw inner diameter flattering blade 7 for performing a cutting process for flattening the crest of the inner thread. As is apparent from FIG. 1, the female screw inner diameter flattering blade 7 is provided with the biting portion 2 of the threaded portion 3.
Is formed from the portion immediately after to the portion near the center.

FIG. 5 is a sectional view showing a state in which a female screw is machined on a workpiece using the tapping tap of the above embodiment. As shown in FIG. As the biting portion 2 at the tip end of the portion 1 bites into the threaded hole 9 of the workpiece 8 and the tap enters the depth of the threaded hole 9, first, the screw of the biting portion 2 is formed. The pilot hole removing blade 6 performs a cutting process in which the preliminary screw hole 9 is spirally exposed by its trapezoidal shape, and the thread of the thread processing portion 3 of the preliminary screw hole 9 having the original inner diameter d1 follows. The helical portion is finished to a predetermined inner diameter equal to the outer diameter of the screw-down hole flattering blade 6, and then the thread forming section 3 raises a screw thread into the screw-down hole 9 having the predetermined inner diameter to form the female screw 10
Is formed, and the female screw inner diameter flattering blade 7 of the threaded portion 3 performs a cutting process for flattening the crest of the raised thread, and the inner diameter d2 of the female screw 10 is changed to the outer diameter of the female screw inner diameter flattering blade 7. Equal predetermined dimensions. Then, three grooves 5 extending from the leading end portion to the trailing end portion of the screw portion 1 and used for forming the screw-down hole razor blade 6 and the female screw inner-diameter razor blade 7 are formed by the cutting work by these blades. A small amount of swarf is placed in those grooves. In addition, the groove 5
It also has a function of supplying lubricating oil to each thread of the thread portion 1 to reduce tapping torque.

Therefore, according to the raised tap of the above embodiment, the following remarkable effects can be obtained. (1) Even when the screw hole diameter d1 is smaller than the lower limit of the screw hole diameter tolerance when a conventional tapping tap is used, the screw hole drilling blade 6 exposes the screw hole 9 to a predetermined inner diameter. , The dimensional tolerance of the screw pilot hole diameter d1 can be expanded on the lower limit side as compared with the prior art, so that the machining of the screw pilot hole 9 can be facilitated, and the screw pilot hole diameter at the center of the dimensional tolerance can be improved. d1 can be set smaller than before,
Insufficient internal diameter of the female screw due to an excessive increase in the internal diameter of the female screw due to insufficient thread ridge rise can be effectively prevented, and the effective diameter of the internal screw can be stabilized. (2) Even when the threaded hole diameter d1 is small, the threaded portion 3 raises the thread to form the female screw 10 after the threaded hole flattening blade 6 has rubbed it and finished it to an appropriate inner diameter. Excessive bulging of the thread can be reliably prevented, and the life of the raising tap and the breakage of the raising tap due to an increase in tapping torque can be reliably prevented. (3) As the threaded portion 3 raises the thread to form the female screw 10, the female screw inner diameter wiping blade 7 of the threaded portion 3 lifts the crest of the raised thread to form a female screw.
Since the inner diameter d2 of the 10 is set to a predetermined size, the target inner diameter of the female screw can be obtained stably, and by appropriately selecting the shape of the female screw inner diameter wiping blade 7, the crest of the female screw thread is required. Accordingly, it can be processed into a predetermined round shape or a flat shape as in the illustrated example. (4) Even when the screw hole 9 is a tapered cast-out hole, the thread processing portion 3 raises the screw thread in the screw hole 9 that is finished by the screw lower hole wiping blade 6 to have an appropriate inner diameter. Female screw
Forming 10, the female screw inner diameter wiping blade of the threaded part, according to which, the inner diameter of the female screw 10 is set to a predetermined size by exposing the crest of the raised screw thread, so that the female screw inner diameter d2 without taper is obtained. In addition to this, it is possible to reliably prevent the screw thread from rising too much, and thus to prevent the service life of the tapping tap from shortening due to an increase in the tapping torque and to reliably prevent breakage.

In addition, according to the tapping tap of the above embodiment, since the female screw inner diameter flattering blade 7 is formed from the portion immediately after the biting portion 2 of the threaded portion 3, the threaded portion 3 of the threaded portion 3 is formed. In parallel with the portion immediately after the biting portion 2 raising the screw thread, the female screw inner diameter flatter blade 7 formed in that portion scrapes the raised screw thread from the first thread, and therefore, the machining It is possible to reliably prevent the tapping torque from increasing due to the crest of the female screw 10 hitting the bottom of the threaded portion 3.

According to the raised tap of the above embodiment,
The screw portion 1 has protrusions 4 for controlling the raising action at three places in the circumferential direction, and three grooves 5 are formed on the protrusions 4 adjacent to each other.
The female screw inside diameter wiping blade 7 that wipes the crest of the thread raised by the protrusion 4 can be easily formed by using the groove 5 because of the circumferential position of the groove 5. it can.

Further, according to the raised tap of the above embodiment, since the three grooves 5 extend linearly in parallel to the axis of the tap, the processing of the grooves 5 is facilitated. Can be.

In the following, a specific example in the case where the nominal size is M6 × 1 will be described. General dimensions such as the total length of the tapping tap, the length of the screw portion 1 and the outer diameter of the shank portion of the above embodiment are as follows. However, the dimensions of the screw-down hole flattening blade 6 and the female screw internal diameter flattening blade 7, which are particularly provided in this embodiment, are the same as those of the conventional tapping tap of the same nominal size, respectively. mm
It has been.

As a result of the present inventor performing internal thread processing with the forming tap of the above embodiment having the dimensions of the specific example, in the case of the conventional forming tap, the screw hole diameter is 5.50 mm to 5.55 mm.
In contrast, the tolerance was a small value of 0.05 mm.
Even though it is 5.30mm to 5.55mm and the tolerance is as large as 0.25mm, the inside diameter of the screw hole 9 (screw hole diameter) is larger than the diameter 5.4mm of the screw 6 of the biting portion 2 If it is small, the screw prepared hole wiping blade 6 of the biting portion 2 is
In a spiral shape, and thereafter, the helical portion followed by the thread of the threaded portion 3 is finished to a predetermined inner diameter equal to the outer diameter of the screw-drilling blade 6, and then the threaded portion 3
The protruding portion 4, which is located rearward in the rotation direction from the screw-drilling blade 6, raises a thread in the screw-drilled hole 9 having a predetermined inner diameter to form a female screw 10, and in parallel with the screw, The 5.0 mm diameter female screw inner diameter wiping blade 7 of the thread processing part 3
The top of the raised thread is exposed, so the inner diameter
A 5.0 mm female screw 10 was obtained stably. Also,
In the case where the pilot hole 9 is a cast hole, if both the inlet (large diameter end) and outlet (small diameter end) dimensions are within the range of 5.30mm to 5.55mm, the same processing as above can be performed. , The tapping could be used without pre-machining.

By the way, in the case of the cutting tap, the screw hole diameter is 4.917 mm to 5.153 mm and the tolerance is 0.236 mm. Therefore, in the case of the above embodiment in the above specific example, the screw hole diameter tolerance is cut. It can be said that the size can be made equal to or larger than the tap.

Although the present invention has been described with reference to the illustrated examples, the present invention is not limited to the above-described example. For example, in the above-described embodiment, in the above-described embodiment, the screw-down hole spirals in a trapezoidal shape. However, the screw hole may be entirely exposed by a linear shape, and the screw portion has four or more circumferentially projecting portions for controlling the raising action. Alternatively, the groove may extend spirally along the axis of the tap. And it goes without saying that the tapping tap according to the present invention can also be applied to a tapping size other than the nominal size in the above specific example.

[Brief description of the drawings]

FIG. 1 is a side view showing one embodiment of a raising tap according to the present invention.

FIG. 2 is a cross-sectional view showing a cross-section along a screw thread including a screw-threaded hole flattening blade at a part II (bite-off part) of the tapping tap of the embodiment shown in FIG.

FIG. 3 is a cross-sectional view showing a cross section along a screw thread including a female screw inner diameter wiping edge in a part III (thread processing part) of the tapping tap of the embodiment shown in FIG. 1;

FIG. 4 is a cross-sectional view showing a cross section along a screw thread in an IV section (thread processing section) of the forming tap of the embodiment shown in FIG. 1;

FIG. 5 is a cross-sectional view showing a state in which a female screw is machined on a workpiece using the raising tap of the embodiment.

6 (a) is a side view showing an example of a conventional tapping tap, and FIG. 6 (b) is a cross-sectional view along the thread of the tapping tap.

[Explanation of symbols]

 Reference Signs List 1 thread part 2 biting part 3 thread processing part 4 protrusion 5 groove 6 screw prepared hole razor blade 7 female screw inner diameter wrench blade 8 workpiece 9 screw prepared hole 10 female screw d1 original bore diameter of screw prepared hole d2 female screw bore

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-155640 (JP, A) JP-A-57-18927 (JP, U) JP-A-63-189526 (JP, U) Machinery and tools, industry Issued by the Investigation Committee, issued on April 1, 1997, April issue, Vol. 41, No. 4, (58) Field surveyed (Int. Cl. ⁷ , DB name) B23G 5 / 06,5 / 20 B23G 7 / 00,7 / 02

Claims (6)

(57) [Claims] 1. A raised tap having a threaded portion at a tip portion and a threaded portion connected to the threaded portion in a threaded portion, at least extending from a tip portion to a rear end portion of the threaded portion. A single groove, a screw-down hole flattening blade formed by using the side wall of the groove in the biting portion, and performing a cutting process to expose a screw-down hole; and using the side wall of the groove for the thread forming portion. Formed
A tapping screw, characterized by having a female screw inner diameter flattering blade that performs cutting processing to cut off the peak of the raised screw thread. 2. The tapping tap according to claim 1, wherein the internal thread internal flattening blade is formed at least in a portion of the threaded portion immediately after the biting portion. 3. The screw part has three protrusions in the circumferential direction for controlling a raising action, and the grooves are provided between the protrusions adjacent to each other. Claim 1 or Claim 2
The raised tap described. 4. The screw portion has four protrusions in the circumferential direction for controlling a raising action, and the grooves are provided between the protrusions adjacent to each other. Claim 1 or Claim 2
The raised tap described. 5. The tapping tap according to claim 1, wherein the groove extends linearly in parallel with the axis of the tap. 6. The tapping tap according to claim 1, wherein the groove extends spirally along an axis of the tap.