JPH02160597A - Manufacture of ballpoint pen tip - Google Patents

Abstract

PURPOSE:To reduce wear of a tool at the time of cutting and restrain the generation of burrs by performing a nitriding treatment in the process of producing a ballpoint pen tip by the use of a small diameter pipe made of a ferritic stainless steel. CONSTITUTION:A tip part of a small diameter pipe 1 made of a ferritic stainless steel is squeezed to form a reduced diameter tip part 2, and the pipe 1 is subjected to a nitriding treatment. Then, an inner surface part of the reduced diameter tip part of the pipe 1 is subjected to cutting by a tool inserted through a tip opening, whereby a ball-holding hole 3, a ball mount 4, an ink guide 5 and the like are provided. Finally, a ball 6 is fitted into the ball-holding hole 3, followed by caulking. Since an inner surface part of the caulked part 7 is free of burrs arising from cutting, stable caulking can be achieved, resulting in that a ball-holding force, an ink outflow quantity, a writing feeling and the like are stable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a ballpoint pen tip made of ferritic stainless steel.

(Prior art) Conventionally, the method of manufacturing a ballpoint pen tip from a thin metal tube made of ferritic stainless steel is to first form the tip by plastic working so that it becomes gradually narrower toward the tip, and then to cut the inner surface of the tip. , form the ball holding hole, ball pedestal, ink guide groove, etc., then insert the ball into the ball holding hole, and finally the tip of the ball holding hole,
The ball was caulked to bend inward to prevent the ball from being pulled out.

(Problem M to be solved by the invention) Ferritic stainless steel not only has inferior machinability compared to copper-based metals and causes greater wear and tear on tools, but as a result, it also has the tendency to cause cracking, which has a great impact on quality. Has characteristics that make it easy to occur. In particular, the flakes that occur on the inner surface of the tip of the tapered part become an obstacle to the subsequent crimping process, making the crimping process unstable, causing problems such as variations in the ball-holding force of the ballpoint pen tip and the amount of ink flowing out. there were. Therefore, the present invention extends the life of the tool during cutting, suppresses the occurrence of flakes, and makes it possible to perform stable caulking, thereby creating a high-quality ballpoint pen tip with less variation in ball holding power and ink flow rate. The purpose is to provide a manufacturing method.

(Means for Solving the Problems) In order to achieve the above object, the method for manufacturing a ballpoint pen tip of the present invention is based on the conventional process in which the tip of a thin metal tube made of so-called ferritic stainless steel is first shaped into a tip by plastic working. The ball is formed so as to gradually become narrower as it goes toward the tip, and then a ball holding hole, a ball pedestal, an ink guide groove, etc. are formed by cutting on the inner surface of the tip, and then the ball is inserted into the ball holding hole. Finally, tighten the periphery of the tip of the ball holding hole.
It is characterized by adding a nitriding process to the process of crimping the ball inward to prevent it from being pulled out. Here, the nitriding treatment refers to a method commonly used in the past.

(Function) When a nitriding process is applied to a ferritic stainless steel metal tube, the hardness increases by about 40% to 50% and the ductility decreases by about 30%. This action reduces the occurrence of built-up edges during cutting, thereby reducing wear and tear on the tool, and also suppresses the occurrence of burrs due to changes in the material.

(Example) 1. Ferritic stainless steel f! as shown in Figure 1.
The tip of the metal capillary tube (1) made of No. 4 is narrowed over its entire length so that it gradually narrows toward the tip, and as shown in Figure 2, the tip of the metal tube (1) is tapered ( 2
) to form.

Thereafter, this metal tube (2) is subjected to a conventional nitriding process. After that, a metal capillary tube (2
) using a tool from the tip opening on the inner surface of the tapered part of the tip.
Cutting is performed to form ball holding holes (3) as shown in Figure 3.
) Forming the ball pedestal (4), ink guide (5), etc. Finally, as shown in Figure 4, insert the ball (6) into the ball holding hole (3) and insert the ball (6) into the ball holding hole (3).
The process is completed by performing a so-called caulking process in which the peripheral edge of the tip of step 3 is pressed inward and bent. During this caulking process, there is no burr on the inner surface of the caulking part (7) due to the cutting process in the previous process, so stable caulking can be performed.

2. First, a conventional nitriding process is performed on a metal 'S tube (1) made of ferritic stainless steel 81 as shown in No. 111J. Afterwards, this nitrided metal tube (
The tip of 1) is narrowed over its entire circumference so that it gradually narrows toward the tip, forming a tapered part (2) at the tip of the metal capillary tube (1) as shown in FIG. Using a tool from the tip opening, cut the inner surface of the tapered end of the metal tube (2) to form a ball holding hole (3), a ball pedestal (4) and an ink guide (
5) Form etc. Finally, as shown in Figure 4, insert the ball (6) into the ball holding hole (3) and insert the ball (6) into the ball holding hole (3).
The process is completed by performing a so-called caulking process in which the peripheral edge of the tip of step 3 is pressed inward and bent. During this caulking process, there is no burr on the inner surface of the caulking part (7) due to the cutting process in the previous process, so stable caulking can be performed.

(Effects of the Invention) Since the present invention is configured as described above, it brings about the effects described below.

Since no cracks occur in the caulking part due to the cutting process, stable caulking can be performed, which increases the ball retention force.
Ink flow rate, brush feel, etc. are extremely stable.

Productivity has been greatly improved due to less wear and tear on tools, and ballpoint pen tips made of relatively durable stainless steel are now available.
Obtained cheaply.

In addition, the increased hardness improves the wear resistance of the tip of the ballpoint pen tip that contacts the paper surface, and the wear resistance of the ball holding part that holds the rotating ball when writing is also improved. This has the effect of significantly extending the writing life.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the metal tube before plastic working, Figure 2 is a cross-sectional view of the metal tube after plastic working, Figure 3 is a cross-sectional view of the metal tube after cutting, and Figure 4 is the finished state of the chip. Cross section, 5th
The figure is a graph showing the hardness of each part of a metal capillary tube after plastic working, with and without nitriding treatment. (1)...metal thin tube, (2)...tapered part (3)...
・Ball holding hole, (4)...Ball pedestal, (5)...
・Ink guide groove, (6)...Ball, (7)...
Caulking part. Patent applicant: Mitsubishi Pencil Co., Ltd. (6)...Ball (force...caulking part missing★Island 65 phrase U skin)

Claims (1)

[Claims] A method for manufacturing a ballpoint pen tip, characterized in that a nitriding treatment is performed during the process of manufacturing a ballpoint pen tip using a thin metal tube made of ferritic stainless steel.