JPH0475816A - Spiral fluted tap - Google Patents

Abstract

PURPOSE:To prevent wear of the thread ridge of a machined female screw by applying chamfering on the part on the base end side, on the side where a lateral rake angle is positive, of the cutting edge of the chamfer of a spiral fluted tap and applying negative relieving of a frank continued to the cutting edge. CONSTITUTION:In a spiral fluted tap 10, a thread ridge 16 formed such that an incomplete shape is gradually changed for a complete shape from the tip of a chamfer 20 toward a complete thread port 18 is peripherally divided by a helical flute 22, and a cutting edge 30 is formed to the one end part of the thread ridge 16 along the helical flute 22. In the spiral fluted tap 10, chamfering 52 is applied on a cutting edge 30, on the side where a lateral rake angle is positive, of the cutting edge 30 along flanks on both sides of the thread ridge 16 of the chamfer 20. Or, negative relieving is applied on a flank continued to the cutting edge 30. Thus, during a work to cut a female screw, cutting having reduced resistance and high precision is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement of a helical groove tap for cutting a female thread, and particularly relates to a technique for preventing double twisting in the thread of a female thread that has been cut. .

Conventional technology A type of thread cutting tap has a spiral thread that changes from an incomplete shape where the top is shaved off to a perfect shape as it goes from the tip of the tapered chamfer to the complete thread. The helical cutting edge is divided in the circumferential direction by the helical groove, and a spiral cutting edge is formed along the helical groove on one end of the divided thread, that is, on the ridge line between one end face formed by the dividing and the helical flank surface. There is a twisted groove tap that is made up of.

In such a helical groove tap, the cut chips are discharged through the helical groove toward the rear or the front in the advancing direction of the tap. Based on the axial component of the cutting force generated by this process, a forward or backward thrust force acts on the helical groove tap, causing the actual lead of the helical groove tap to advance too far beyond the correct lead, which is equal to the pitch of the thread. There may be delays. For this reason, the cutting edge digs into the threads of the female thread that have already been partially cut, cutting more than the normal cutting 2, and creating a ridge on the female thread 1-2 that has been formed. This is one of the factors that reduce the accuracy of internal threads.

In order to prevent this type of female thread from collapsing on the crest of the female thread, the present applicant applied for a tap with seven threads and grooves.
Publication No. 76156. =In the 61st case of disclosure,
Of the cutting edges along the flanks on both sides of the thread, the side where the side rake angle is positive, that is, the side that is pressed against the female thread 7 by the thrust force, is chamfered or 2. Apply a negative first cut to the flank following the cutting edge. : From the 4th knee, the above-mentioned female thread (limiting the biting into the 2nd part 1) is torsionally grooved, to eliminate over-advancement or delay of the 2nd part, and to prevent the formed female thread from double-crossing. It has become.

Problems U7 or L7' and 4 that the invention attempts to solve are the above-mentioned conventional threaded and grooved taps!
: , J:; By applying the above chamfering or double chamfering, the original cutting ability of the cutting edge along one flank of the mount is sacrificed. In particular, the cutting resistance of the chamfered cutting edge where main cutting is performed is large, resulting in poor cutting quality and the tendency for the cutting surface to become rough. There was an inconvenience that the machining accuracy of the two formed female threads (7) was adversely affected.

The present invention has been made against the background of the following circumstances, and its purpose is to enable accurate and consistent near cutting without impairing the inherent cutting properties of the cutting edge. Do you offer twisted groove taps? , there are two.

Means for Solving the Problems The gist of the present invention to achieve the object is to provide a screw thread whose shape changes from an incomplete shape to a perfect shape as it goes from the tip of the chamfer to the complete thread. In a helical groove tap, which is divided in the same direction from the helical groove A and a cutting edge is formed at one end of the divided groove along the first groove A, the thread in the chamfered portion is Among the cutting edges along the flanks on both sides of the mountain, for the cutting edge on the side where the side rake angle is positive, the proximal side edge 1 is chamfered. It is located in the second position, which is a negative second counter to the flank.

Operation and Effects of the Invention In the above-mentioned helical groove tap, the cutting edge on the side where the side rake angle is positive in the chamfered part where cutting is mainly performed, the tip side part of the flank part is normally The shape is approximately the same as that of the cutting edge, but the proximal part that is not involved in cutting is chamfered on the inner circumferential side, that is, the proximal part that does not participate in cutting except for the tip side part, or the flank that continues from the cutting edge is chamfered. Negative second control is applied to . For this reason, during stamp cutting, the distal end portion maintains good sharpness and cuts with high precision with less cutting resistance, while the proximal end portion maintains good sharpness, while the proximal end portion is chamfered. In other words, the negative number limits the biting into one female thread, making it more accurate! Since the self-guiding action that allows the helical groove tap to advance is fully achieved, double-seam of the internal thread can be reliably prevented.

However, unlike conventional helical groove taps that prevent ridges from collapsing, they sacrifice the original cutting ability of the cutting edge, shortening the life of the tap, and adversely affecting machining accuracy due to the force of the female tap. This makes it possible to perform sharp, high-precision round cutting with an accurate lead, without any deviation or τ.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

Fig. 1 shows a groove tap 1 which is an embodiment of the present invention.
0, the helical groove tap 10 has a male threaded portion 12 on the tip side that performs helical cutting, and a tool C such as a tap holder (not shown) = shank portion 1 on the side to be held.
It consists of 4. The male threaded portion 12 is provided with threads +-1- and +16 corresponding to the female threads to be formed, extending 2 times around the axis so as to form predetermined screw holes and notches. This twisted groove Yu/2 pu 10 right-handed female cat 7
The thread 16 of the male thread 12 is formed on the right thread L7. This male threaded portion 12 has a complete threaded portion 18 whose outer diameter is constant and the height of the thread 16 is approximately equal, and a complete threaded portion 18 which has a constant outer diameter and a tip side (4
The screw thread 16 is formed into a tapered shape so that the top of the thread 16 changes from an incomplete shape to a perfect shape as it goes from the tip to the complete thread 18. There is.

Further, the male threaded portion 12 is provided with three helical helical grooves 22 having a helix angle α around the axis of the helical groove tamp 1°, and the thread 16 is rotated in the circumferential direction by the helical grooves 22. Three equally spaced lands 24, 26.2
It is divided into 8 parts.

The winding direction of the spiral is right-handed, and the helical groove tap 1o of this embodiment is of a so-called right-handed screw type. The front ends of the land portions 24°26.28 in the right-handed rotation direction, that is, on the ridge line between the front end surface in the rotation direction formed by the division and the flank surface of the thread 16, The cutting edge 3° along the helical groove 22 is formed in a spiral shape. This cutting edge 3o
The chips cut by the tap are discharged through the helical groove 22 to the shank 14 side, that is, to the rear side of the helical groove tap 1o.

Cross-sectional views of each cutting edge 30 in which the land portion 24.2628 of the chamfered portion 20 is cutting a female thread in a workpiece are shown in the upper, middle, and lower rows of FIG. 2 in the order of cutting progress of the helical groove tap 10. Although each cutting edge 30 of the chamfered portion 20 is incomplete as a heel, each cutting edge 30 performs cutting at the same cutting depth, and the entire chamfered portion 20 and A complete internal thread is formed by cutting the first complete thread 18a of the complete thread portion 18.

In addition, the meshed parts in Fig. 2 correspond to each cutting edge 3.
The cutting amount is 0.

FIG. 3 shows an enlarged view of a portion of the cutting edge 30 that corresponds to one of the threaded ridges. Cutting is mainly performed at the top of the cutting edge 30, that is, at the outer peripheral portion 3 along the tapered surface of the chamfered portion 20.
1, but also at the tip side portions 36 and 38 of the cutting edge 30 along the leading side flank 32 and the trailing side flank 34 of the helical groove tap 10, which correspond to the cutting depth of the outer peripheral portion 31. It will be done. In addition, by sliding the flanks 32.34 and the flank 40.42 of the partially female thread that has already been cut, self-guidance allows the helical groove tap 10 to be advanced and guided with a lead equal to one pitch of the thread 16. The effect is about to occur.

FIG. 4 shows a plan view of one incomplete gold mine 44 including the cutting edge 30 shown in FIG. 3, that is, a view seen from the outer peripheral side of the helical groove tap 1o. Here, the cutting edge 30 of the advancing side flank 32
The respective lateral rake angles of the cutting edges 30 of the trailing flank 34 and the trailing flank 34 are
On the side thereof, it is a positive value α (same as the helix angle α of the helical groove 22), and on the trailing side flank 34 side it is a negative value −α. Therefore, in the helical groove tap 1o, a thrust force directed toward the advancing side is generated in connection with the cutting action of the spiral cutting edge 3o corresponding to the helical groove 22, so that the cutting edge 3o of the advancing side flank 32 It tends to bite into the flank 4o of the internal thread, which has already been partially cut.

The rear side of the outer peripheral portion 31 of the cutting edge 30 in the right-handed rotation direction, that is, the outer peripheral surface facing the heel 46, is provided with a relief angle in the tangential direction to reduce friction, suppress heat generation, and improve sharpness. A relief surface 48 is provided for the purpose of improving surface accuracy. The clearance angle is generally between 3° and 12°. In addition, 56 in FIGS. 3 and 4 is the screw thread 1.
It is the bottom of 6.

As mentioned above, the leading side flank 32 has a positive side rake angle.
Although the cutting edge 30 tends to bite into the flank 4o of the female thread relatively easily, in the helical groove tap 10 of this embodiment, the inner peripheral side of the tip side portion 36 that performs the cutting action hardly participates in cutting. A chamfer 52 is provided at the base end portion 5o. As shown in FIGS. 3 and 4, this chamfer 52 is made so that the cutting edge 3o is dropped in a straight line from the boundary point with the tip side portion 36, and the chamfer 52 is designed to reduce the flank of the female thread during cutting. It has a function to limit the digging into the 40.

That is, the already partially formed internal thread flank 4
0, the proximal end portion 5o is slid while being pressed by the thrust force, but since the chamfering 52 is applied, the proximal end portion 500 is pressed against the flank 40 of the female thread 1.
It is difficult for the material to bite.

Further, in FIG. 5, which is a cross section within the cutting depth range including the tip end portion 36,38 of the cutting edge 30, the relief angle θ of the relief provided on the flank 32 and the flank 34 is normally 0.5°. However, in this example, it can be set to a large value of 1' to 2 degrees, and the tip side portion 3
6.38! The cutting resistance in the cutting is significantly reduced.

In this part, immediate thread cutting is performed with good sharpness and high surface accuracy. In addition, in FIG. 5, if the lateral rake angles α and ˜α in the respective cutting directions in the flank 3234 are smaller than the lateral rake angles α and −α with respect to the straight line parallel to the axis, the lead angle of the helical thread 16 is It's off by just that.

On the other hand, in FIG. 6, which is a cross section outside the cutting depth range including the proximal end portion 50.54 of the cutting edge 30, the relief angle θ2 of both flanks 32.34 is equal to the relief angle θ1 in FIG. and Roma (-7 magnitude).

As described above, the female threaded flank 4 is formed by the chamfer 52.
By preventing biting into the threaded groove tamp 10, the helical groove tamp 10 is accurately guided by the flanks 40 and 42 of the female thread, and a self-guiding action that advances with the correct lead is reliably obtained. It is possible to set the clearance angles θ, θ2 as large as about 1' to 2° at the distal end portion 36 and the proximal end portion 50 on the 32 side.

Further, the complete thread portion 18 is provided with a cutting edge 30 and flanks 32, 34 in the same manner as the thread 16 (incomplete thread 44) in the chamfered portion 20, and the land portions 24, 2 are provided with a cutting edge 30 and a flank 32.
6.28, there are many consecutive complete peaks 58.

SoL7te1. : Regarding these perfect ridges 58 as well, regarding the cutting edge 30 on the flank 32 side where the side rake angle is positive,
A chamfer 60 is provided with the cutting edge 30 dropped over the entire length from the tip to the base where cutting is performed. Note that the top and both flanks 32. of the complete mountain portion 18.
The relief angle of No. 34 is 0.5° or less.

Further, only the first complete peak 18a is cut at the tip side portion 3, which is cut in the same manner as the incomplete gold peak 44 in the biting portion 20.
6, the cutting edge 30 is chamfered 52 at the proximal end portion 50 on the inner peripheral side than the distal end portion 36, and the clearance angle θ1. Relief surfaces of θ and O are similarly provided.

The helical groove tap 10 configured as described above is attached to a tap holder or the like, and is screwed from the tip side into the lower diameter pre-formed on the workpiece to remove the eclipse (unfinished gold mine in the hole 20, etc.). Cutting is performed by the cutting edge 3o at the first complete peak lea.At this time, a thrust i/force directed toward the tap tip side is generated in connection with the cutting of the spiral cutting edge 3o corresponding to the helical groove 30. Since the chamfer 52 is provided on the advancing side flank 320 and the toe side portion 50 of the cutting edge 30, the biting of the female thread into the flank 40 is limited, so that the cutting edge 30 can be cut with an accuracy equal to the pitch of the thread 16. Accurate self-guiding action is achieved in which the helical groove tap advances, and double-separation of the internal thread is reliably prevented.

In addition, in the helical groove tap 10 of this embodiment, the chamfer 52 is not provided on the tip side portion 36 of the flank 32, and a relief with a relief angle θ larger than usual is formed, so that good sharpness is achieved. As a result, high-precision thread cutting can be performed, and the surface accuracy of the female thread and tap life are improved.

Although one embodiment of the present invention has been described in detail above, the present invention can also be implemented in other embodiments.

For example, in the above-described embodiment, the cutting edge 304 in the center 304 was chamfered 52 on the proximal end portion 50 of the 32 flanks, but the cutting edge 30 was
The flank 32 may be held back to a position of 30° (see FIG. 6) on the inner side of the cutting edge 2, and a negative countermeasure may be provided on the flank 32 following the 30° cutting edge. In this case as well, it is possible to obtain the same effects as in the above embodiment. Also,
The chamfer 52 may be in the shape of a rounded corner obtained by rounding the cutting edge of the cutting edge 30.

Further, in the above-mentioned embodiment, the flank 32 is
Although the chamfer 52 is applied to the entire proximal end portion 50 on the side, it is not always necessary (for example, the chamfer 52 is applied only to the cutting edge 30 of a part of the threaded thread 16, or the proximal end portion 50 is chamfered. Any part of the side portion 50 may be chamfered.In short, it is sufficient that the chamfer or negative chamfer be applied to such an extent that the female screw bits into the flank 40 are restricted.

Also, in the embodiment described above, both flanks 32.
34 distal portion 36.38 and proximal portion 50.5
4, relief angles of relief angles θ1° and θ2 were provided respectively, but these relief angles θ1. θ2 may be changed as appropriate, and may have different sizes, or may be different on the leading side flank 32 side and the trailing side flank 34 side. Further, the relief may be provided only on the side of the flank 34 where the side rake angle is negative, or the relief may not be provided on both flanks 3234.

In addition, in the embodiment described above, the three right-handed helical grooves 22
Although the helical groove tap 10 has been described, the number of helical grooves can be changed as appropriate, and the present invention is similarly applicable to a helical groove tap having a left-handed helical groove and a helical groove tap that cuts a left-handed internal thread. can be done. That is, in a right-handed helical groove tap having a left-handed helical groove, the proximal portion of the cutting edge along the trailing flank, excluding the distal portion where cutting is performed, is chamfered,
Negative countermeasures can be applied to the flank on the proximal side of the tap, and if a helical groove tap for left-handed threads has a left-handed helical groove, the right-handed helical groove can be applied to the leading side flank. If grooves are provided, chamfering or negative chamfering may be applied to each trailing side flank.

In addition, in the above-described embodiment, the threads 16 in the complete thread portion 18 are as follows, except for the first complete thread 18a.
Although the entire cutting edge 30 of the flank 32 from the tip to the base is chamfered 60, the chamfering 60 is not necessarily an essential requirement.

In addition, in the above-mentioned embodiment, the helical groove tap 10 was described for cutting a female thread in which the thread troughs form a trapezoidal shape. The ridge shape can be changed as appropriate, and the present invention can be similarly applied to the helical cross-sectional shape of the helical groove tap determined accordingly.

Others - Although not illustrated, the present invention can be modified and modified based on the knowledge of those skilled in the art without departing from the spirit thereof.
It may be implemented in a modified manner.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a helical groove tap that is an embodiment of the present invention. FIG. 2 is a diagram illustrating the shape of the cutting edge at the chamfered portion of the helical groove tap shown in FIG. 1, and is a diagram showing the cutting state by each land in the order of cutting progress. FIG. 3 is a diagram illustrating in detail one cutting edge in the chamfered portion of the helical groove tap shown in FIG. 1. FIG. 4 is a plan view of the incomplete gold mine having the cutting edge shown in FIG. 3, viewed from the outer circumferential side. FIG. 5 is a sectional view taken along line 1-V in FIG. 3, and is a diagram for explaining the shape of the cutting edge at the tip side portion where cutting is performed. FIG. 6 is a cross-sectional view taken along v+-■ in FIG. 3, and is a diagram for explaining the shape of the cutting edge, etc. of the proximal end portion that is not involved in cutting. : Helix groove tap: Thread double-bit part: Cutting edge: Tip side part double chamfer 18: Complete thread part 22: Helix groove 32.34: Flank 50: Base end part

Claims (1)

[Claims] The thread, which changes from an incomplete shape to a perfect shape as it goes from the tip of the chamfer to the complete thread, is divided in the circumferential direction by a helical groove, and one end of the divided thread is placed along the helical groove. In a helical flute tap with a cutting edge configured to A helical groove tap characterized in that a portion is chamfered or a flank following the cutting edge is chamfered with a negative second chamfer.