JPH08141843A - Thread cutter - Google Patents

Abstract

PURPOSE: To eliminate chips positively and form a thread of high accuracy without needing to form a prepared hole. CONSTITUTION: A thread cutting edge 13 is provided at the periphery of the tip of a shank 1, and a hole cutting edge 16 is formed at the tip face of a thread chaser in such a way as to be continuous onto the radial inner side of the thread chaser from the thread cutting edge 13. A circular recessed part 20 is formed at the center of the tip face of the thread chaser, and a passage 21 is provided being opened to the circular recessed part 20 from the base end face of the thread chaser. The thread chaser is held to the spindle of an NC machine tool enabling the simultaneous three-axis control of a holding part 2, and helically fed to advance one pitch every one revolution while being driven to autorotate and to revolve so as to form a prepared hole by the hole cutting edge 16 and to form a threaded hole by the thread cutting edge. Chips are eliminated by jetting compressed air, a coolant, and the like into the circular recessed part 20 through the passage 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread cutting tool for forming a screw on a work.

[0002]

2. Description of the Related Art A tap is generally used as a tool for forming an internal thread on a work. The tap has a shank tip threaded portion, and a tap corresponding to a desired screw hole is selected and used.

When forming a female screw using a tap, a prepared hole having the same diameter as the inner diameter of the female screw is formed in the work by a drill or the like as a pre-process, and then the screw is formed by the tap. And, especially when the hole that forms the female thread is a stop hole, when the pilot hole is formed, the chips remaining in the pilot hole may damage the tap due to the resistance, and the accuracy of the female thread may deteriorate. To prevent it from falling, compressed air, coolant, etc. are blown into the prepared hole to eliminate chips.

On the other hand, there has been proposed a so-called drill tap in which a pilot hole is formed as a pre-process and a screw is continuously formed by a single tool. As shown in FIG. 7, this drill tap is one in which a drill 31 is continuously provided at the tip of the tap 30, and is driven in synchronization with rotation and feed to form a prepared hole by the drill 31. Subsequently, the tap 30 forms a screw.

Further, as disclosed in JP-A-4-152020, there is also known one in which a screw is formed by helically feeding a tool to which one or more cutting blades are attached. This tool has a diameter smaller than the diameter of the pilot hole, is attached to the spindle of an NC machine tool that can simultaneously control three axes, and is driven to rotate and helically fed along the pilot hole while being helically fed to produce an internal thread. Is formed. This type of tool has a degree of freedom in the diameter and pitch of the screw to be formed by helically feeding the tool, and the tool rotation speed suitable for the work can be selected.

[0006]

However, among the above-mentioned conventional techniques, particularly when a tap is used or a tool which is helically fed is used, a screw hole is used as a pre-process for forming a screw. It is necessary to form a pilot hole of diameter. And these conventional techniques need to prepare a tool for forming a pilot hole and a tool for forming a screw, respectively, and the time and effort for exchanging a tool such as a drill for forming a pilot hole. Is inefficient because it requires
Further, there is a problem that when the tool is replaced, the axis of the tool is displaced and the accuracy of the screw may be reduced.

Among the above-mentioned conventional techniques, the tap has a tap having a pitch and a screw diameter corresponding to the screw to be formed, and a tool for forming a prepared hole such as a drill suitable for the tap. The problem is that different taps and drills must be used for different thread diameters, and different taps must be prepared for the same thread diameter but different pitches. was there. And, especially when the screw hole is a blind hole, the chips left in the hole when forming the pilot hole may become resistance, which may reduce the accuracy of the screw or damage the tool. There is a problem that equipment for removing the chips inside the prepared hole before forming the pit and labor for removing the chips are required. Furthermore, when forming multiple screws for a workpiece, the chips from the removed pilot holes may enter other pilot holes, so it is necessary to remove the chips each time before forming the screws. There was also the problem of being there.

Further, among the above-mentioned conventional techniques, in the case of the drill tap, it is not necessary to separately prepare a tool such as a drill for forming the pilot hole and the tap, but similar to the case of the tap, the tap hole is used. It is necessary to prepare the one corresponding to. Also, since the preparation of the prepared hole and the formation of the screw are performed continuously, it is necessary to drive the rotation and the feed in synchronization, and the cutting load when forming the prepared hole of the drill is large. It is difficult to remove the powder, and it is suitable for forming a screw hole penetrating a thin work, but there is a problem that it is difficult to use when the screw hole is a blind hole.

Further, among the above-mentioned conventional techniques, in the one in which a tool is helically fed, there is a degree of freedom in the diameter and pitch of forming a screw, but if the tool is adapted to a small screw diameter, the size of the tip is increased. However, there is a problem that the rigidity of the tool is significantly reduced due to the small size.

The present invention has been made in view of the above problems, and does not require forming a prepared hole as a pre-process,
The degree of freedom in the diameter and pitch of the formed screw is large, the number of revolutions and the cutting amount suitable for the work can be selected, the chips can be reliably removed, and the screw with high precision can be formed. An object is to provide a thread cutting tool that can be used.

[0011]

In order to solve the above-mentioned problems, a thread cutting tool according to the present invention is provided with a thread forming means on the outer periphery thereof, and is helically fed while being driven to rotate and also to be revolved relatively to a work. A thread cutting tool, characterized in that a prepared hole forming means is provided radially inside the thread forming means on the tip surface of the tool, and a chip removing means that opens at the tip of the tool is provided. is there.

[0012]

The assembling apparatus of the present invention, which is configured as described above, is driven to rotate and also revolves relatively to the work, and is helically fed so as to advance one pitch per revolution, and While forming the prepared hole by the hole forming means, the screw is formed by the screw forming means on the outer circumference. The rotation speed of rotation can be selected as the rotation speed suitable for the work,
The pitch of revolution and helical feed can be set according to the desired screw dimensions. The chips generated by the prepared hole forming means and the screw forming means are removed by ejecting compressed air, coolant or the like from the tool tip opening of the chip removing means.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a thread cutting tool according to the present invention is shown in FIG.
It will be described with reference to FIG. In the drawings, the same reference numerals denote the same or corresponding parts.

As shown in FIG. 1, the thread cutting tool according to the present invention is provided with a holding portion 2 on the base end side of a shank 1, a blade portion 3 on the tip end side thereof, and a chip removing means opened at the tip of the tool. It is provided with 4.

The holding unit 2 is an NC capable of simultaneously controlling three axes, such as a machining center capable of helical feed and a milling machine.
It is held on the main shaft of a machine tool, and its shape is formed so as to fit the holder.

The blade portion 3 comprises a screw forming means 7 provided on the outer periphery of the tool and a prepared hole forming means 8 provided on the tip end surface of the tool. In the case of this embodiment, the thread forming means 7 is provided with four lands 12 with a straight groove 11 sandwiched in the circumferential direction of the tool, and three rows of thread cutting are performed in the direction orthogonal to the tool axis of each land 12. A blade 13 is formed. This thread cutting blade 13
4, has a triangular shape with a thread height H in the radial direction at a predetermined pitch P and has a tool diameter D _T. As shown in FIG. 2, each thread cutting edge 13 is provided with an outer peripheral relief having an angle β so as to be temporarily reduced in diameter with respect to the rotation direction of the tool, and the rake face has a rake angle of a predetermined angle (not shown). Has been provided.

As shown in FIGS. 1 and 4, the prepared hole forming means 8 has a hole cutting blade 16 formed on the end surface of the tool so as to be continuous from each screw cutting blade 13 inward in the radial direction of the tool. Is. The hole cutting edge 16 has a length l _c , as shown in FIG.
It is formed so as to incline upward in the radial direction at an angle θ _R with respect to a plane orthogonal to the rotation axis of the tool, and as shown in FIG. Has been. Assuming that the diameter of the intersection of the thread cutting edge 13 and the hole cutting edge 16 is the cutting edge diameter D _C , the cutting edge diameter D _C is set as in the following equation. Edge diameter D _C ≦ Tool diameter D _T − Thread height 2H

In the chip removing means 4, a circular concave portion 20 is formed at the center of the prepared hole forming means 8, and a passage 21 which opens from the end face on the holding portion 2 side to the circular concave portion 20 over the entire axial length of the tool is formed. It is provided. The tool base end side opening of the passage 21 is
Supply device for compressed air and coolant (not shown)
Is connected.

As shown in the plan view and front view of the locus of the blade portion 3 in FIGS. 5 and 6, a thread cutting tool having a tool diameter D _T has the holding portion 2 mounted on a spindle such as an NC milling machine capable of helical feed. Held and driven to rotate, and screw diameter D _N
It is revolved driven by the revolution diameter D _K along the (revolution diameter D _K = D
_N- D _T ). Then, the thread cutting tool is helically fed at an inclination of the lead angle θN of the screw to be formed, and is relatively moved with respect to the work so as to advance by one pitch for each revolution.

The hole cutting edge 16 is set to have a radial inclination angle θ _R with respect to a plane orthogonal to the rotation axis of the tool larger than an inclination angle θ _N which is helically fed. If the cutting width of the hole cutting edge 16 is l _o , the cutting width l _o can be obtained by the following equation. Cutting width l _o = (D _C · sin θ _N · cos θ _R ) / [s
in (θ _N + θ _R )] Then, the length l _c of the hole cutting edge 16 is set to be larger than the cutting width l _o . Further, in order to make the chip pocket larger than the cutting width lo of the hole cutting edge 16, on the surface opposite to the rake surface of the front row of the screw cutting edge 13, as shown in FIG. It is provided at an angle γ.

As shown in FIG. 4, the work 25 has an angle θ _N.
The threaded tool to be helical feed in the direction of an arrow at an inclination, the screw holes in the threading cutting width plus the cutting length L ₂ of the cutting length L ₁ and the hole cutting 16 of the blade 13 L is formed. The chips generated by the cutting process of the screw cutting blade 13 and the hole cutting blade 16 have a large chip pocket due to the clearance angle γ, so compressed air, coolant, etc. are supplied from these supply devices via the passage 21 to the tool tip. It is ejected to the circular concave portion 20 and is reliably removed from between the work and the tool. After forming the desired screw hole, the tool is moved to the axial center of the screw hole so as not to interfere with the screw hole, and retracted to the standby position linearly or by helical feed.

In the thread cutting tool according to the present invention, the thread cutting portion 7 is provided with four lands 12 with a straight groove 11 sandwiched in the circumferential direction of the tool, and three rows of thread cutting blades 13 are formed on each land 12. Although described by way of example, the present invention is not limited to this embodiment. For example, the straight groove 11 may be a spiral groove, the number of lands 12 may be two or three, and the screw cutting blade 13 may be a single row. Alternatively, there may be two rows or four rows or more.

In the case where the screw cutting blade 13 is a single row, it is possible to form a screw hole having an arbitrary pitch and diameter by adjusting the helical feed amount.
In the case of multiple rows, it is possible to form screw holes having the same pitch but different diameters.

Furthermore, although the thread cutting tool according to the present invention has been described in this embodiment in the case of forming a screw hole, a male screw is formed by being spirally fed while rotating around a rod-shaped periphery. You can also

In the thread cutting tool according to the present invention, the rotation speed of rotation can be set according to the material of the workpiece and the desired machining accuracy of the screw, and the revolution diameter can be set according to the desired screw diameter, and further desired. The helical feed amount can be set by the screw pitch.

[0026]

According to the present invention, since the hole cutting blade is formed inside the screw cutting blade on the end face of the tool, it is not necessary to form the prepared hole as the previous step, and the desired diameter and pitch can be obtained. A screw can be formed, and moreover, a screw can be formed according to a work.

Further, according to the present invention, since the compressed air, the coolant and the like can be ejected by providing the chip removing means which is opened at the tip of the tool, the chips can be surely removed. A highly accurate screw can be formed.

[Brief description of drawings]

FIG. 1 is a front view of a thread cutting tool according to the present invention.

FIG. 2 is a bottom view showing an end portion of the thread cutting tool according to the present invention.

FIG. 3 is a perspective view showing a blade portion of the thread cutting tool according to the present invention.

FIG. 4 is an enlarged cross-sectional view showing an operating state of a blade portion of the thread cutting tool according to the present invention.

FIG. 5 is a plan view showing a movement trajectory of a blade portion of the thread cutting tool according to the present invention.

FIG. 6 is a front view showing a movement trajectory of a blade portion of the thread cutting tool according to the present invention.

FIG. 7 is a front view of a conventionally used drill tap.

[Description of sign]

 1 Shank 3 Blade 4 Chip removal means 7 Screw forming means 8 Pilot hole forming means 13 Screw cutting edge 16 Hole cutting edge

Claims (1)

[Claims] 1. A thread cutting tool, which is provided with a screw forming means on its outer periphery and is helically fed while being driven to rotate while being orbitally driven relative to a workpiece, wherein the screw forming means on the tip end surface of the tool is formed. A thread cutting tool characterized in that a prepared hole forming means is provided inside in a radial direction, and a chip removing means opened at a tip of the tool is provided.