JPH055320U - Center drill - Google Patents

Abstract

(57) [Summary] [Purpose] Even if the workpiece is cemented carbide or other cemented carbide material,
An object of the present invention is to provide a center drill that has a short processing time and can improve work efficiency. [Structure] A shank 1 is provided with a tip 2 made of a quadrangular pyramid-shaped single crystal diamond, the base edge side cutting edge ridge 3 of the tip 2 has an opposite angle of 60 ° to 90 °, and the tip side cutting edge ridge 4 has a The center drill has an ridge angle of 90 ° to 130 °. When the tip 2 of the rotating center drill is pressed against the work piece, an obtuse-angled conical center hole is bored in the work piece by the tip-side cutting edge ridge 4 of the tip. With the side cutting edge ridge 4 serving as a guide, the center hole is machined into an acute-angled conical shape by the base end side cutting edge ridge 3.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention mainly relates to a center drill for machining a conical center hole in a cemented carbide material such as cemented carbide.

[0002]

[Prior Art]

 Center hole machining of a work piece is an important task in cylindrical grinding because it directly affects the machining accuracy. Generally, a dedicated center drill is used to machine a center hole in a workpiece, and a conical center hole is machined in the workpiece.

However, if the work piece is a cemented carbide material such as a cemented carbide, it cannot be processed by a general center drill. This cemented carbide is a composite metal obtained by sinter-bonding carbide powder of Group IVa, Va, and VIa metals with an iron-based metal such as Fe, Co, or Ni, and among 9 types, WC-Co. System alloys have the best mechanical properties. This type of cemented carbide is mainly used for cutting tools, impact resistant tools, etc., but in order to drill holes in this cemented carbide, it has traditionally relied solely on electrical discharge machining.

The electric discharge machining is a machining method in which an electrode having a hole shape to be machined is used, an electric discharge is generated between the electrode and the machined object, and the surface is scraped by the action of the electrode. However, expensive equipment such as an electric discharge machine is required.

Further, a drill in which a quadrangular pyramid diamond tip is provided at the tip of a shank is also known. This tip can be used for drilling with each edge serving as a cutting edge, but the work piece is made of a super hard material In this case, the tip of the quadrangular pyramid tip is broken and cannot be used.

[0006]

[Problems to be solved by the device]

 As mentioned above, if the workpiece is cemented carbide or other cemented carbide material, it cannot be machined with a normal cutting tool, so we relied on EDM, but EDM requires a long machining time and Inefficient. Furthermore, the surface of the electric discharge machining becomes rough, and a lot of time is required for finishing, and expensive electric discharge machines and other equipment are required.

The present invention has been made in view of the above circumstances, and its purpose is to shorten the processing time and improve the work efficiency even if the workpiece is a cemented carbide material such as cemented carbide. The purpose of the present invention is to provide a practical center drill that is suitable for mass production because it can be improved, has a smoother machined surface than electrical discharge machining, and has a low machining cost and is practical.

[0008]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention, in a center drill for processing a conical hole in a work piece, provides a shank with a chip made of quadrangular pyramid-shaped single crystal diamond, and the base end side of this chip. The opposite edge angle of the cutting edge is 60 ° to 90 °, and the opposite edge angle of the tip side cutting edge is 90 ° to 130 °.

[0009]

[Action]

 When the tip of the rotating center drill is pressed against the work piece and fed, the tip edge side of the chip makes an obtuse-angled conical center hole in the work piece, and when the machining progresses further. The tip-side cutting edge ridge serves as a guide to form the center hole into an acute-angled conical shape.

[0010]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. 1 to 3, reference numeral 1 denotes a shank of a center drill, and a tip 2 is fixed to the tip of this shank 1. This tip 2 is made of a single crystal diamond in the shape of a quadrangular pyramid, and the ridge angle a of the base end side cutting edge ridges 3 ... Is formed at an acute angle of 60 ° to 90 °, and the tip side cutting edge ridges are formed. The opposite ridge angle b of 4 ... Is formed at an obtuse angle of 90 ° to 130 °.

Here, since the tip 2 has the shape of a quadrangular pyramid, the four base-side cutting edge ridges 3 are provided at 90 ° intervals, as shown in the front view of FIG. The opposite ridge angle, that is, the angle a formed by the opposite cutting edge ridges 3a and 3c among the base end side cutting edge ridges 3 ... and the angle a formed by 3b and 3d are shown in a side view in FIG. As shown, it is formed at an acute angle of 60 ° to 90 °.

Similarly, since the tip 2 has the shape of a quadrangular pyramid, the apical-side cutting edge ridges 4 ... Are cross-shaped and provided at 90 ° intervals, as shown in the front view of FIG. The opposite ridge angle, that is, the angle b formed by the opposite cutting edge ridges 4a and 4c and the angle b formed by 4b and 4d among the tip side cutting edge ridges 4 ... As shown by, it is formed at an obtuse angle of 90 ° to 130 °.

Here, the opposite ridge angle of the tip-side cutting edge ridge 4 is set to 90 ° to 130 °, because when the angle is 90 ° or less, the tip portion is easily broken when processing the cemented carbide, and When the obtuse angle is more than °, it has the effect of preventing breakage, but the sharpness is reduced, and this has been confirmed by the experiment by the present applicant.

The tip 2 is fixed to the shank 1 by the following fixing method. That is, a tip attachment hole is formed in the tip surface of the shank 1 to the extent that the tip 2 is inserted, and after the tip attachment hole is filled with a bronze bond, the tip 2 is inserted and sintered to fix the tip. To do. Alternatively, it is fixed by the active metal method.

The active metal method is a method of wetting the tip 2 with an active metal obtained by mixing titanium into silver wax and chemically brazing to the shank 1, and generally in a vacuum or an argon gas atmosphere, Brazing at temperature. This active metal method has the advantages that the joint surface exhibits high strength, and the entire surface other than the joint surface is exposed, so the cutting edge can be polished as it is and chips can be easily removed.

The shank 1 of the center drill configured as described above is mounted on the head of a boring machine and rotated at 600 to 1200 rpm, and the tip 2 is pressed against a cemented carbide material 5 such as cemented carbide which is a workpiece. When abutting and feeding are applied, as shown in FIG. 4, a cone-shaped center hole 6 is bored in the cemented carbide material 5.

At this time, since the apex side cutting edge ridge 4 of the tip 2 has an obtuse opposite angle, an obtuse conical hole is bored in the cemented carbide material 5, and when the machining further progresses, this obtuse angle is formed. The conical hole is processed into an acute conical hole by the base-side cutting edge 3 having an acute opposite angle. Therefore, the tip side cutting edge ridge 4 located in the conical hole serves as a guide, and the conical center hole 6 is bored in the cemented carbide 5 by the base side cutting edge ridge 3 having an acute opposite angle. ..

In addition, in the above-mentioned one embodiment, the case where the center hole is machined in the cemented carbide material such as cemented carbide has been described, but it goes without saying that it can be machined also in a general steel material. Moreover, the tip 2 is not limited to natural diamond, and may be artificial diamond.

[0019]

[Effect of the device]

 As described above, according to the present invention, the shank is provided with a chip made of a quadrangular pyramid-shaped single-crystal diamond, and the ridge angle of the base end side cutting edge ridge of the chip is set to 60 ° to 90 °. The opposite ridge angle of the cutting edge is formed to be an obtuse angle of 90 ° to 130 °. When the tip of the rotating center drill is pressed against the work piece, an obtuse-angled conical center hole is bored in the work piece by the tip edge cutting edge of the tip. The center edge is machined into an acute-angled conical shape by the base-edge-side cutting edge using the cutting edge as a guide. Therefore, even if the work piece is a cemented carbide or other cemented carbide material, the machining time is short and the work efficiency can be improved, so it is suitable for mass production and the machined surface is smoother than that of electrical discharge machining. Therefore, there is an effect that it is possible to provide a practical center drill with a lower processing cost.

[Brief description of drawings]

FIG. 1 is a side view of a chip according to an embodiment of the present invention.

FIG. 2 is a front view of the chip of the example.

FIG. 3 is a side view of the center drill of the embodiment.

FIG. 4 is an explanatory view of a processed state of the embodiment.

[Explanation of symbols]

1 ... Shank, 2 ... Tip, 3 ... Base edge cutting edge, 4 ... Tip edge cutting edge.

Claims (1)

[Claims for utility model registration] [Claim 1] In a center drill for processing a conical hole in a workpiece, a shank is provided with a chip made of quadrangular pyramid-shaped single crystal diamond, and the base end cutting of this chip is performed. A center drill characterized in that the opposite ridge angle of the blade edge is set to 60 ° to 90 °, and the opposite ridge angle of the tip side cutting edge ridge is formed to be an obtuse angle of 90 ° to 130 °.