JP2001018120A - Screw machining tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw machining tool formed by unifying a hole before threading machining drill and a cold forming tap. SOLUTION: A drill part 2 is provided with a drill tip part having a diameter capable of machining a hole before threading appropriate for plastic working of a screw of a tap 1, and the periphery of the drill part 1 is provided with a screw groove 21 without generating interference with the screw formed by plastic working in the tap part, and a land 12 having a width formed at 0.9-2.2 of ratio in relation to the screw groove width of the screw groove 8, and a margin 13 formed so that a total width of the margin as a part of the land 12 is 30% or more of width of the whole periphery. The screw groove is formed at the same pitch with the screw of the tap and an effective diameter and a diameter of a valley part thereof are formed smaller by 0.02 P-20 P than the effective diameter of a perfect thread part and the diameter of a valley part thereof, and furthermore, a back taper of the periphery in the screw groove length is formed at 0-0.015 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for drilling and tapping a screw in a single step.
Further, the present invention relates to a tap with a drill provided with a tap portion connected to the drill portion, and more particularly to a screw working tool using a raised tap for forming an internal thread by plastic working without a cutting edge in the tap portion.

[0002]

2. Description of the Related Art There are casting, burring, and the like in the preparation of a prepared hole which is a pre-process of female thread processing, and the most common processing is by a drill. Normally, pilot holes and screws are machined in separate processes, but since multiple tools, holders and holder storage parts are required, and time for tool replacement is required, a drill is provided at the tip of the tap to integrate the pilot holes and screws. In recent years, the use of a tap with a drill that enables machining with a single tool has increased. FIG. 5 shows a tap 30 with a drill in which a hand tap and a drill for drilling a prepared hole are integrated. The hand tap 34 has a handle portion 31 and a screw portion 33 having a cutting edge 32 on the outer periphery. A drill part 35 is connected via a small-diameter connection part 36. FIG. 5 shows a tap 40 with a drill in which a spiral tap and a drill for drilling a prepared hole are integrated. The tap 40 has a handle portion 31 and a screw portion 43 having a cutting edge 42 as in FIG. A drill part 35 is provided at the tip of the spiral tap 44
Connected through. In addition, the tap with a drill is also called a drill tap.

[0003] By using such taps with drills 30 and 40, a pilot hole is machined by a drill portion 35, and then female threads are machined by cutting edges 32 and 42 of connected taps 33 and 43. After the completion of the threading, the drilled tap is pulled out of the work while being reversed, so that the pre-drilling and the female threading are performed with one tool. Further, in the threading with such a cutting tap, the pilot hole diameter drilled by the drill portion 35 is the same as the thread diameter, so that it does not change before and after threading. Therefore, even if the tapping with the drill is reversed after the screw processing and the tap is returned, the outer peripheral portion of the drill does not interfere with the thread. Therefore, since the drill portion and the tap portion perform their functions as independent tools without interference during use, exactly the same shape data as the drill alone and the tap alone can be applied to each portion. That is, a cutting tap can be a tap with a drill simply by adding a drill portion to the tip of the tap.

[0004] On the other hand, in order to eliminate cutting chips at the time of screw processing or to enhance screw strength, a tapping tap for forming a screw by plastic flow of a work material regardless of a cutting edge is used. However, when machining a female thread with a cutting tap, the pilot hole uses a drill with the same diameter as the internal diameter of the internal thread, while a shaping tap uses a drill to form a female thread by the plastic flow of the work material. It is also required that the precision of the pilot hole diameter be high. The diameter of the drill for preparing a pre-drilled hole is a diameter close to the effective diameter of the screw. Further, after the internal thread is formed, the workpiece material forms the internal diameter of the internal thread due to plastic flow, so the internal diameter of the internal thread becomes smaller because it is formed from the drill diameter for preparing a pre-drilled hole. Sometimes, the outer periphery of the drill interferes with the thread formed by plastic flow. For this reason, a tap with a drill cannot be obtained simply by providing the drill portion at the tip of the raised tap. Therefore, a thread groove that does not interfere with the thread formed by the plastic flow is provided on the outer periphery of the drill, and the outer periphery of the drill and the thread may be prevented from interfering when the tap after the threading is reversed and returned. .

[0005]

However, the provision of a thread groove on the outer periphery of the drill alone cannot secure the precision of drilling the prepared hole, adversely affects the precision of threading, and also increases the accuracy of thread return. There is a problem that the surface is easy to grind and a desired screw precision cannot be obtained. In view of the above problems, an object of the present invention is to combine a drill and a forming tap which can obtain a clean and stable plastic machined screw equivalent to the screw processing of the forming tap alone even in the process of forming a screw specific to the forming tap. To provide a threaded tool.

[0006]

According to the present invention, there is provided a drill portion having two or more twisted grooves at one end, a tap portion connected to the drill portion via a connecting portion to form a thread, and a tap portion. In the threading tool having a connecting handle and a tapping part, the tap part is a raised tap for forming a female thread by plastic working, and the drill part has a diameter capable of forming a pilot hole suitable for plastic working of the internal thread of the tap. The ratio between the screw groove formed so as not to interfere with the screw thread formed by the tap portion on the outer periphery of the drill portion and the twist groove width is 0.9 to 2.2. The above-mentioned problem is solved by providing a land and a margin in which the total width of the margin as a part of the land is 30% or more of the entire outer circumference (each margin width is preferably the same width). did.

If a thread groove is provided on the outer peripheral portion of the drill, one corner of the drill cutting edge will be chipped, and the preparation of the prepared hole will be unbalanced and the prepared hole diameter will be unstable.
This slight change in the diameter of the pilot hole greatly affects the swelling state of the screw formed by plastic flow. In the present invention, the land having a ratio of 0.9 to 2.2 with respect to the twist groove width, and the total width of the land margin is 30% or more of the entire outer periphery (each margin width is preferably the same width). ), So that the drill can be supported by the margin even if the corner is missing, the guideability of the outer circumference is improved, and the prepared hole is stable even if the cutting force becomes unbalanced. Processing becomes possible, and a highly accurate pilot hole can be obtained.

When the ratio of the twist groove width to the land width is less than 0.9, the twist groove width is small, and it is difficult to discharge cutting chips at the time of preparing a pre-drilled hole. When the ratio exceeds 2.2, the land width is small. Too unstable. Therefore, the ratio between the width of the twist groove and the width of the land is set to 0.9 to 2.2. If the total width of the margins is less than 30% of the entire outer circumference, the cutting edge of the drill is chipped due to the thread groove, and the cutting resistance becomes unbalanced, and the drilled hole becomes enlarged or distorted, resulting in instability. The total width of the margin portion is set to be 30% or more of the entire outer circumference so as to obtain a stable pilot hole by improving the guideability of the above. In general, a land of a drill is composed of a margin and a second trimming surface.
%, It is possible to provide a low-priced product by omitting the second preparation step.

The thread groove formed so as not to interfere with the plastically machined thread by the tap portion provided on the outer periphery of the drill portion is a thread groove having the same phase as the pitch of the forming tap, and when the tap is reversed, Since the flank face is formed by a tap, it is formed so as not to contact the flank face of the screw. However, if the effective diameter and the diameter of the valley are too small, the outer periphery of the drill may be chipped or a margin may not be secured. On the other hand, if the size is too large, it is likely to come into contact with the formed flank surface, and there is a possibility that the formed screw or the outer periphery of the drill may be damaged due to cutting chips or plastic processing chips being inserted.

Therefore, in claim 2, the screw groove is formed as follows.
The screw and pitch of the raising tap are the same, and the effective diameter and the diameter of the valley are 0.02P to 0.20P respectively (P = pitch m) from the effective diameter and the diameter of the valley of the complete peak of the raising tap.
m) It was made small.

Although there is a slight difference due to the plastic fluidity of the material, the amount of rise of the thread is uniquely determined by the diameter of the prepared hole, so that the height of the thread and the inner diameter of the internal thread are determined. Therefore, stable preparation of the prepared hole is required for the raised tap. Therefore, the guideability of the outer periphery is improved by making the margin larger than that of a general drill, but the outer back taper in the drill length is further reduced to 0 in the twist groove length of the drill portion.
By setting the thickness to 0.015 mm, the guideability is further enhanced and the stability of the prepared hole diameter is improved. In the drill, the drill itself enters into the processed hole, and in order to prevent welding due to rubbing with the processed surface of the hole, the margin is generally narrowed, and the outer back taper is set to 0.04 mm per 100 mm.
Above. In the present invention, since the thread groove is formed on the outer periphery of the drill, the amount of contact between the machined surface and the outer periphery of the drill is small, and the permeability of the cutting oil is good, so that the margin is wide and the outer outer back taper is eliminated to improve the outer guideability. Can be.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1A and 1B are explanatory views showing an embodiment of a threading tool according to the present invention, in which FIG. 1A is a side view, FIG. 1B is a front view as viewed from the front end side, and FIG. FIG. 2 is a partially enlarged explanatory view in the vicinity of a connection portion where a drill portion and a tap portion in FIG. 1 are connected to each other. In the example shown in FIG. 1, a twisting drill (twist drill) 2 having a pair of twist grooves is provided at the tip of a raising tap. As shown in FIG. 1, the thread working tool of the present invention includes a raised tap portion 1, a drill portion 2, and a handle portion (a shank portion) 3. As shown in FIG. 2, a biting portion 5 is formed at the tip of the raised tap portion 1, and the drill portion rear end 6 is formed.
And a connecting portion (neck) 7 is formed. The tap portion 1 is the same as a conventional raised tap, and as shown in FIG. 1C, a convex radial portion 1a for forming a screw thread and an escape portion 1 having an effective diameter smaller than the radial.
b are arranged in four equal parts. In FIG. 1 (c), the cross section of the escape portion is simplified.

[0013] The outer diameter (diameter) 2d of the drill portion is dimensioned such that the thread catch rate is 80 to 95% because it is machined. The minimum diameter of the pilot hole is when the thread engagement rate of the machined screw is 100%. As the pilot hole diameter increases, the thread engagement rate of the internal thread decreases. The drill diameter is determined from the range of the required catch rate. Generally, the size is larger than the effective screw diameter. In the biting portion 5 of the raised tap, the threads 5a and 5b are formed so that the effective diameter is gradually reduced from the complete thread 1a... 1a of the tap portion 1, and the biting tip outer diameter 5d is the outer diameter of the drill portion 2. It is smaller than 2d. A thread groove 2 is provided on the outer circumference 2a of the drill portion 2.
1, the pitch of the thread groove is the same as the pitch of the thread of the raised tap, the effective diameter of the thread of the thread groove and the diameter 21a of the valley are raised, and the effective diameter of the complete crest of the tap and the diameter of the valley 1c Respectively, are formed smaller by 0.02P to 0.20P. The thread groove on the outer periphery of the drill portion is formed continuously with the biting portion 5, but the effective diameter of the screw from the biting portion to the drill portion is continuously increased at the connecting portion 7. Note that the effective diameter of a screw means a diameter of a cylinder such that when a screw thread is cut by a cylindrical surface around the axis of the screw, the width of the screw thread portion is equal to the width of the thread groove portion.

The drill portion has a pair of twist grooves 8, a chisel 9, a cutting edge 10, a corner 11, a land 12, a margin 13 and the like as in a general twist drill, but in the example of FIG. There is no counting surface. That is, the land is used as a margin as it is. Further, a back taper of preferably 0 to 0.015 mm is provided in the direction of the twist groove length L. A similar effect can be expected with a double margin drill having two margins on one land instead of having a large margin. In addition, it is sufficient that a margin width is secured comprehensively even in a case having three or more twist grooves. In other words, the gist of the present application is that, by having a thread groove on the outer periphery, there is no deterioration of the machined surface due to rubbing with the work material, and even if the cutting edge corner is unbalanced by securing a margin width, etc. The guide width is made large and the guide hole supports the guide.

Next, a machining method using such a thread machining tool will be described. FIG. 3 is a partially enlarged cross-sectional view showing a state in which a female screw is inserted into a work and the internal thread is subjected to plastic working after preparation of a pre-drilled hole, and FIG. It is a partial expanded sectional view showing the state where a tool is removed from a work. In FIG. 3, the drill portion 2 is rotated into the work 31, and the prepared hole 32 of the work is machined. The inner diameter 32d of the pilot hole 32 is formed by the outer diameter 2d of the drill.
As the drill part 2 and the tap part 1 of the threading tool enter, the pilot hole 32 is formed between the bite parts 5d and 5c of the tap part 1.
The internal thread 33 is plastically formed on the work 31 in the order of 5c, 5b, 5a, and the complete thread 1a.
The plastic working is completed with a. The internal diameter 33d of the female screw of the work is machined slightly larger than the diameter 1c of the valley of the complete peak of the raised tap.

After the machining of the female thread of the predetermined length is completed, FIG.
As shown in the figure, the female screw 33 has a thread 1a
The pitch is the same as a, 5a to 5d, and this pitch is the same as the pitch of the thread groove 21 of the drill portion 2.
Further, the inner diameter 33d of the female screw is made larger than the diameter 21d of the root of the thread groove. Therefore, the thread working tool can be easily removed from the work 31 without interference between the female screw 33 and the drill portion 2, and the drill and the tap can be integrated with each other despite the raised tap. Needless to say, after the start of biting and when the tool is removed from the workpiece, the rotation and the feed are controlled to values suitable for screw machining.

[0017]

As described above, in the threading tool of the present invention, the tap portion is a raised tap, and the ratio of the screw groove to the twist groove width on the outer periphery of the drill portion is 0. By providing a land having a width of 9 to 2.2 and a margin such that the total width of the land margin is 30% or more of the entire outer periphery, stable irrespective of chipping of a corner portion. Since a high-precision prepared hole can be obtained by preparing a prepared hole, we provide a thread processing tool that combines a drill and a prepared tap that can obtain a clean and stable plastic processing screw equivalent to the screw processing with a raised tap alone. It became something to do. Furthermore, even though the tap is a raised tap, since a single tool can perform from the preparation of a pre-drilled hole to the threading, the processing time can be reduced and the cost can be reduced. For example, the conventional processing time of about 35 seconds when separately using a prepared hole and a tapping tap is shortened to 15 seconds by the threading tool according to the present invention.

Further, the effective diameter and the diameter of the valley are raised, and the effective diameter and the diameter of the valley of the complete crest of the tap are 0.02P respectively.
Since it was formed to be smaller by 0.20P and the interference between the plastically processed screw and the drill portion was minimized, a plastic screw with higher precision could be processed with one tool. Further, the back taper of the outer circumference in the twist groove length of the drill portion is set to 0 to
By setting the thickness to 0.015 mm, a more stable preparation of the prepared hole was made, and a more accurate screw processing became possible.

[Brief description of the drawings]

FIG. 1A is a side view showing an embodiment of a thread working tool of the present invention, FIG.
(C) is a sectional view taken along the line AA of (a).

FIG. 2 is a view showing an embodiment of the thread working tool of the present invention.
FIG. 5 is a partially enlarged explanatory view of the vicinity of a connection portion where a drill portion and a tap portion are connected.

FIG. 3 is a partially enlarged cross-sectional view showing a state in which the female screw is inserted into a work and plastic drilling of the internal thread is performed after drilling a prepared hole.

FIG. 4 is a partially enlarged cross-sectional view showing a state in which the female thread working tool of the present invention is removed from the work after the internal thread is plastically worked on the work.

FIG. 5 is a side view of a conventional tap with a drill in which a hand tap and a drill for drilling a prepared hole are integrated.

FIG. 6 is a side view of a conventional tap with a drill in which a spiral tap and a drill for drilling a prepared hole are integrated.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tap part 1c Diameter of valley of complete peak of raised tap 2 Drill part 2a Outer circumference of drill part 2d Diameter (outer diameter of drill part) 3 Handle part 7 Connection part (neck) 8 Twist groove 12 Land 13 Margin 21 Thread groove 21d Diameter of root of thread groove L Length of torsion groove of drill part

Claims (3)

[Claims] 1. A screw having a drill portion having one or more twisted grooves at one end, a tap portion connected to the drill portion via a connection portion to process a screw, and a handle portion connected to the tap portion. In the working tool, the tap portion is a raised tap that forms a female screw by plastic working, and the drill portion has a tip portion having a diameter capable of forming a pilot hole suitable for plastic working of the female screw of the tap, A screw groove formed on the outer periphery of the drill portion so as not to interfere with the screw because it is plastically worked by the tap portion; and a land having a ratio of the twist groove width to a width of 0.9 to 2.2, And a margin provided so that the total width of the margins that are part of the lands is 30% or more of the entire outer circumference. 2. The thread groove has the same pitch as the screw of the raising tap, and the effective diameter and the diameter of the valley are respectively 0.0 times smaller than the effective diameter and the valley diameter of the complete crest of the raising tap.
2. The thread working tool according to claim 1, wherein the diameter is reduced by 2P to 0.20P (P = pitch mm). 3. The thread working tool according to claim 1, wherein a back taper of an outer circumference of the drill portion at the length of the torsion groove is 0 to 0.015 mm.