JPH09192930A - Thread cutter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease cutting load per cutting edge by setting the twist angle of the cutting edge in the same direction as the conditions of the cutting edge and in the prescribed angle range, and performing threading at high speed even when a threaded hole has the small diameter. SOLUTION: A main body 1 is made of solid hard alloy and provided with a blade part 2 on one end and a cylindrical shank 3 on the other end. Since the twist angle in the range of 15 deg. to 35 deg. is applied to the cutting edge of the blade part 2 in the same direction as the conditions of the cutting edge, cutting is performed by the positive face angle having good sharpness in longitudinal feed. Since the clearance angle is set in the range of 6 deg. to 10 deg., a sufficient clearance is provided and the sharpness is improved even when a hole has the small diameter. As a result, deformation by cutting force can be restrained, and high-speed cutting is made possible without generating deformation on the hole even if the hole has the small diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread cutting mill used for forming a thread by milling, and more particularly to a thread cutting mill capable of processing a screw hole having a diameter smaller than M14 instead of a tap.

[0002]

2. Description of the Related Art Threads are manufactured differently depending on the size of the thread. A large diameter male screw is a bite, a female thread is a boring bite,
In addition, male threads with a small diameter are roughly divided into dies, and female threads with taps. Of these, for dies and taps, only tools with the same diameter as the screw can be used, so when working on multiple dimensions at the same time, it is necessary to prepare many types of tools, which complicates the work and increases the tool cost. I arrived. As a new method, numerical control machine tools (hereinafter NC
Machine) has a well-established method of processing threads by milling using the helical cutting function that combines circumferential feed and axial feed, and the thread milling machine used for that purpose has become known. This method is characterized in that the pitch accuracy and the effective diameter of the screw can be adjusted.

As an example of the conventional thread cutting milling machine, there is a blade exchange type thread cutting milling machine equipped with one blade having a cutting edge having a thread-shaped contour, and a tap-like straight blade multi-blade threading milling machine. is there. The blade exchange type has characteristics that it is suitable for machining large-diameter screws and the maintenance of tools is easy, and the straight-blade type has multiple blades and has excellent machining efficiency. In addition, in addition, the special table 1-502012
There is a combination threading tool shown in No. 1, which is a combination of a threading means and a drilling means and is capable of threading simultaneously with drilling a prepared hole.

[0004]

However, in the conventional thread cutting milling cutter, the blade and the cutting edge are straight blades, so the sharpness is not good, and if the rigidity of the cutting edge is not sufficient, the screw hole is deformed due to tool deformation. There was a problem such as doing.
In particular, the single-edged blade is prone to chatter vibration, and has a problem in machining efficiency, and its use is limited to large-diameter screws. On the other hand, the multi-blade type has an excessive number of blades and tip pockets following the tap, resulting in insufficient tool rigidity, which was insufficient for frequently used small diameter holes. .

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above background and provides a screw hole having a small diameter of less than M14 by imparting a twist to a cutting edge to improve sharpness to reduce cutting resistance. Even so, it is intended to enable high-speed thread cutting. At the same time, the cutting load per cutting edge when feeding the screw hole in the longitudinal direction is reduced, and the end face is chamfered.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises a solid tool material having a thread profile and a cutting edge which is machined in the direction perpendicular to the axis. The milling cutter is such that the twist angle of the cutting edge is in the same direction as that of the cutting edge and in the range of 15 ° to 35 °. Also, the clearance angle of the cutting edge is 6 ° ~
It is set to 10 °. Further, one or two flat ridges lower than the screw ridges are provided at the tip of the thread-shaped cutting edge, and further, one or more bottom blades having a chamfering blade are provided. .

[0007]

According to the present invention, the thread milling machine can be easily manufactured even if it has a small diameter. Further, since the cutting edge is provided with a twist angle of 15 ° to 35 ° in the same direction as that of the cutting edge, the cutting is always started at a positive rake angle with good sharpness at the time of vertical feeding. Since the clearance angle is set to a large angle, even a small diameter hole has sufficient clearance and sharpness is improved. As a result, the deformation due to the cutting force can be suppressed, and even a small diameter hole can be cut at high speed without causing deformation of the hole.

The method of using the thread cutting mill is to give a screw lead from the end face of the screw hole and proceed with cutting, and to insert a milling cutter having a required screw length into the prepared hole, and perform screw processing by one revolution of helical feed. There is a way to end. In the former method of cutting from the end face, since only the thread cutting edge on the tip side of the thread cutting milling cutter makes a round in the cutting, the blade length of the milling cutter can be shortened, but the load concentrates on the portion and damage is quick. In the present invention, since a flat blade having one or two threads lower than the thread is provided at the tip of the cutting edge, the cutting amount is shared by a plurality of threads, so that the load of one blade is reduced and a long distance can be achieved at high speed. It can be cut with. According to the method of shaving from the end surface of the screw hole, the right blade can be downcut with a normal right blade, but the left blade is required with a left screw.
In the present invention, the twist is in the same direction as that of the blade, so that the sharpness is the same as in the case of the right blade. In the case of the method of threading by one-turn helical feed, the blade length is required to satisfy the required thread length. It goes without saying that the blade length may be increased or decreased in the present invention. Hereinafter, the present invention will be described with reference to the drawings showing the embodiments.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the thread milling machine according to the present invention, in which 1 is the main body. The main body 1 is made of solid cemented carbide and has a blade portion 2 at one end and a cylindrical shank 3 at the other end. The blade portion 2 has a diameter of 6 mm, and the cutting blade is a double blade with a right blade and a right twist of 30 °. The blade shape is a screw thread with a pitch of 1.25 mm, and it is arranged in synchronism with the longitudinal direction of the two cutting edges.
A flat blade 6 having a height of 3, 2/3 was provided. The tip of the blade portion 2 is provided with a bottom blade extending to the center of rotation of the milling cutter.
The clearance angle of the cutting edge was 10 °, and grinding was performed using a second cutting tool grinder. The length of the blade is 12 mm, and a hard coating is applied during this period. According to the standard screw standard, a pitch of 1.25 mm is a coarse thread with M8 and M9.
And also with fine threads applied to M10 to M14. These can be processed with one type of thread milling.

The above-mentioned thread cutting milling cutter is attached to a vertical machining center via a holder, and a steel plate having a thickness of 8 mm and having a prepared hole of 6.8 mm in diameter is drilled from the top surface to 1.2 mm.
Helical cutting of radius 4mm with 5mm lead, M8
Was tapped. It was possible to cut at a tool rotation speed of 4000 rpm and a feed of 240 mm / min, and to process in about 40 seconds per hole. Despite repeated cutting, a good quality finished surface with no peeling was obtained. Wear of cutting edge is 2
Since it concentrates near the tip, the re-grinding is only required at the tip. A cut of about 1 mm was made in the radial direction in the same steel plate with the bottom blade coming out from the lower end of the steel plate, and from that condition, the helical function was used to perform cutting with a radius of 4 mm and a vertical feed pitch of 1.25 mm. . The cutting conditions are slow because the work is completed after cutting one round, but the machining time is rather fast. The finished surface is smooth due to the combined use of oily cutting oil. However, tool wear was found on the entire cutting edge. In this way, by performing thread processing with a milling tool, it is possible to perform accurate tapping even for small-diameter screw holes, and use the function of the machining center even for tapping with multiple screw holes. The positional relationship between the screw holes can be accurately performed.

[0012]

As described above, according to the present invention, even a small-diameter thread can be machined with a milling tool, and the thread can be machined at high speed and with high precision.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is an enlarged view of a blade portion of the embodiment shown in FIG.

FIG. 3 is a front view showing another embodiment of the present invention.

FIG. 4 is a front view showing an example of a conventional product.

FIG. 5 is a front view showing another example of the conventional product.

[Explanation of symbols]

 1 Main body 2 Blade part 3 Shank 4 Bottom blade 5 Screw thread 6 Flat blade 7 Chamfering blade α Twist angle

Claims (4)

[Claims] 1. A small-diameter threading milling cutter having a diameter of less than M14, which is made of a solid tool material having a contoured thread shape and a cutting edge which is secondly machined in the direction perpendicular to the axis, and has a helix angle of the cutting edge. 15 in the same direction as the cutting edge
A thread milling machine characterized by having a range of ° to 35 °. 2. The thread milling machine according to claim 1, wherein the clearance angle of the cutting edge is 6 ° to 10 °. 3. The thread cutting mill according to claim 1, wherein one or two flat threads, which are lower than the thread, are provided at the tip of the thread-shaped cutting edge. . 4. The threading milling machine according to claim 1, wherein one or more bottom blades provided with chamfering blades are provided at the tips of the thread-shaped cutting blades.