JPH0985505A - Center and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the joint strength of a cemented carbide tip and shunk by screwing a bolt from the end of the bolt inserting hole through the bolt hole into a female screw in the rear surface of the cemented carbide tip inserted in a tip mount to fix the cemented carbide tip. SOLUTION: A cemented carbide tip 8 formed of a sintered cemented carbide material body only in the conical portion 1 at the tip contacting a material to be cut. A portion 2 embedded in a shunk 9 is made of a cemented carbide alloy. The cemented carbide tip 8 is provided in the rear surface with a female screw 3 in which a bolt 10 is screwed through a bolt hole from the shunk 9 side to be fixed to a tip mount provided in the shunk 9. The portion of the cemented carbide tip embedded in the shunk 9 is formed of cemented carbide alloy or high hardness steel or the like, so that high accuracy female screw working is efficiently performed with a screw-shaped electrode by electric discharging machining.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to a center and a method of manufacturing the center. More specifically, the present invention relates to a center having a large bonding strength between a super-hard tip and a shank, excellent accuracy, and a low defect rate during manufacturing, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A center is a tool for supporting a work material in turning or cylindrical grinding, and frictional heat is generated between the work and a rotating work material, which is easily worn or damaged and may be seized. There is also. The accuracy of the center is an important factor that affects not only the processing accuracy but also the life of the cutting tool and the grinding wheel. For this reason, high-speed steel or cemented carbide is shrunk at the tip of a steel shank to make it sharp, or a super-hard tip such as a diamond sintered body is brazed. Conventionally, an ultra-hard chip for a center has been cut out from a cylindrical sintered body of an ultra-hard material into a conical shape at the tip of a center, embedded in a shank, and brazed by a brazing material. However, according to this method, the loss of the super-hard material when cutting it into a conical shape rather than a cylindrical shape is large, and an expensive super-hard material sintered body is wasted. The present inventors previously used a diamond sintered body as a superhard material sintered body only on the surface of the work piece contacting portion of the center, and using cemented carbide for the embedded portion in the shank. Invented the chip and its manufacturing method, and achieved a great saving of ultra-hard material. However, when this integral sintered tip is brazed to the shank, for example, the thermal expansion coefficient of K10 type cemented carbide is 5.0 × 10 ⁻⁶ / K and the thermal expansion coefficient of the diamond sintered body is 3.9 × 10. ^Since the thermal expansion coefficients of the two differ from each other like ^-6 / K, the diamond sintered body cracks due to the temperature rise to 700 to 750 ° C during brazing and the subsequent cooling, and the strength of the diamond sintered body decreases. There was a case to do.

[0003]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of providing a center having a large bonding strength between a super-hard tip and a shank, excellent precision, and a small defective rate during manufacturing, and a manufacturing method thereof. Is.

[0004]

As a result of intensive studies to solve the above problems, the inventors of the present invention cut an internal thread on the back surface of an ultra-hard chip and form a bolt hole reaching the chip mount from the back surface of the shank. By providing and fixing the ultra-hard chip to the shank with bolts, it was found that it is possible to reliably manufacture a center with high joint strength and excellent accuracy, and based on this finding, the present invention was completed. I arrived. That is, according to the present invention, (1) in a center having a super-hard tip at the tip, the super-hard tip has a female thread on the back surface, and the shank has a bolt insertion hole axially from the back surface of the shank and a chip mount from the tip of the bolt insertion hole. It has a bolt hole reaching up to, and the ultra-hard chip is fixed by screwing the bolt through the bolt hole from the tip of the bolt insertion hole to the female thread on the back of the ultra-hard chip inserted in the chip mount. Center and (2)
Female threads are cut on the back of the ultra-hard chip, and a bolt insertion hole and a bolt hole reaching the chip mount from the tip of the bolt insertion hole are provided axially from the back of the shank. Provided is a method for manufacturing a center, characterized in that a super hard chip is fixed by screwing a bolt into the screw.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 (a) is a cross-sectional view of one embodiment of the super-hard chip used in the present invention, and FIG. 1 (b) is a cross-sectional view of another embodiment of the super-hard chip used in the present invention. In the super-hard tip used in the present invention, only the conical portion 1 at the tip that contacts the work material is made of a super-hard material sintered body, and the shank embedded portion 2 is made of a super-hard alloy. Such a super-hard tip is a female mold corresponding to the conical part,
Filling a mixture of superabrasive grains and binder or powder of sintering aid, or filling the superabrasive grains adjacent to the sintering aid supply source, and forming a cemented carbide in the shank. It can be obtained by injecting an alloy material into contact with the superabrasive grains, heating and pressurizing to sinter between the superabrasive grains, and joining with the cemented carbide material. There is no particular limitation on the superabrasive grains used, and for example, diamond abrasive grains or CBN abrasive grains can be used. As the binder or the sintering aid, for example, powder particles of cobalt, nickel or the like can be used, or superabrasive particles can be obtained by a melt supplied from a cemented carbide or the like forming an embedded portion in the shank. Can be combined. The shape of the tip of the ultra-hard chip used in the present invention is 60 according to JIS B 4112.
The angle is mainly used, but in addition to this, 75 °, 90 °, etc. conforming to JIS B 1011 are appropriately selected. The ultra-hard chip used in the present invention is fixed to the chip mount provided on the shank by providing a female screw 3 on the back surface and screwing the bolt through the bolt hole from the shank side. There is no particular limitation on the method of processing the female thread on the back surface of the ultra-hard tip, but the embedding part of the ultra-hard tip in the shank is
Since it is made of cemented carbide or high hardness steel, it is possible to perform highly accurate and highly accurate internal thread machining by means of electric discharge machining in which the electrode has a screw shape. By tapering the embedded portion of the ultra-hard tip into the shank and the tip mount of the shank, the ultra-hard tip can be firmly fixed to the shank with more accurate positioning. Further, an adhesive may be appropriately used in combination for fixing the taper portion and fixing the bolt.

FIG. 2 is a sectional view of the shank used in the present invention. The outer shape of the shank used in the present invention is not particularly limited, but it is preferable to select the outer shape as a cemented carbide center so as to have a shape corresponding to the JIS B 4112 nominal numbers 0 to 6. The shank used in the present invention has a tapered tip mount 4 for taper fitting with a super hard tip at the tip. The tip mount has the same taper as the embedding part of the ultra-hard tip in the shank, and when the ultra-hard tip is embedded, the tip of the ultra-hard tip and the tip of the shank form a stepless conical surface. And process it continuously. The shank used in the present invention has a bolt insertion hole 5 in the axial direction from the back surface of the shank. The diameter of the bolt insertion hole is not particularly limited, but it is preferable that the bolt has a minimum space sufficient for passing the bolt through the bolt hole, screwing it, and screwing it in using a hexagon wrench or the like. The shank used in the present invention is provided with a bolt hole 6 reaching the tip mount from the tip of the bolt insertion hole. If necessary, between the bolt insertion hole and the bolt hole,
Space can be provided for the bolt head that corresponds to the diameter and height of the bolt head. There is no particular limitation on the diameter of the bolt hole, but according to the diameter of the bolt used, JIS B 1
It is preferable that it is equivalent to the first grade or the second grade defined in 001. FIG. 3 is a side view of one aspect of the bolt used in the present invention. The bolt used in the present invention is not particularly limited, but a bolt having a head 7 such as a hexagon socket head cap screw can be preferably used. The winding direction of the screw thread is not particularly limited, but it is preferable to select the right screw or the left screw in the tightening direction according to the rotating direction of the work material when the center is used. FIG. 4 is a partial sectional view of the center of the present invention. In this figure, a super-hard tip 8 is fixed to a shank 9 with bolts 10. The center of the present invention is
The ultra-hard tip fits into the tip mount in the conical shank recess, is pulled in by bolts, and is fixed by a taper fit, so it is accurately positioned and has excellent dimensional accuracy . According to the method for manufacturing a center of the present invention, since the super-hard tip is joined to the shank by screwing instead of brazing, defects such as wax breakage and cracks due to heat history do not occur.

[0007]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Example 1 An intermediate product of ultra-hard chips having the shape shown in FIG. The conical portion is a superhard material using a diamond sintered body, and the shank embedded portion is made of cemented carbide. A female screw was machined at the center of the back surface of this intermediate product by electric discharge machining to manufacture a super-hard chip having the shape shown in FIG. A shank shown in FIG. 3 having an outer shape corresponding to JIS B 4112 nominal number 4 was machined from a steel material. The chip mount is designed to taper-fit with an ultra-hard chip. Bolt insertion holes and bolt holes are drilled from the back surface of the shank. An ultra-hard tip is taper-fitted to the shank tip mount, and the ultra-hard tip is fixed with a hexagon socket bolt from the bolt insertion hole tip of the shank through the bolt hole to obtain the center of the present invention having the structure shown in FIG. It was The center of this center was inspected for runout at the tip according to JIS B 4115 6.4 and found to be 0.0
It was 005 mm.

[0008]

EFFECTS OF THE INVENTION The center of the present invention secures the super-hard tip to the shank by screwing and does not require heating unlike brazing, so that the joining strength between the super-hard tip and the shank is large, and the manufacturing accuracy is high. Occurrence rate of defective products is low.

[Brief description of drawings]

FIG. 1 is a sectional view of an ultra-hard chip used in the present invention.

FIG. 2 is a cross-sectional view of a shank used in the present invention.

FIG. 3 is a side view of one aspect of a bolt used in the present invention.

FIG. 4 is a partial cross-sectional view of the center of the present invention.

[Explanation of symbols]

 1 Tip-shaped part 2 Tip to be embedded in shank 3 Female thread 4 Chip mount 5 Bolt insertion hole 6 Bolt hole 7 Head 8 Super hard tip 9 Shank 10 Bolt

Claims (2)

[Claims] 1. A center having an ultra-hard tip at the tip, wherein the ultra-hard tip has a female thread on the back surface, and the shank has a bolt insertion hole axially from the back surface of the shank and a bolt hole reaching the tip mount from the tip of the bolt insertion hole. The center is characterized in that the ultra-hard chip is fixed by screwing a bolt through the bolt hole from the tip of the bolt insertion hole into the female thread on the back surface of the ultra-hard chip inserted in the chip mount. 2. An ultra-hard chip is formed with a female thread on the back surface thereof, a bolt insertion hole is provided axially from the back surface of the shank, and a bolt hole reaching the chip mount from the tip of the bolt insertion hole is provided. A method for manufacturing a center, characterized in that an ultra-hard chip is fixed by screwing a bolt into an internal thread on the back surface of the chip.