Lead detent, lead for mechanical pencil, and method for manufacturing lead for mechanical pencil

Abstract

To smoothly insert a lead detent into a tip metal.SOLUTION: A lead-detent to be press-fitted into a pencil tip 50 from behind by a pushing jig A includes, on an inner peripheral surface, a first reduced-diameter portion 63 gradually reduced in diameter toward the front, a parallel hole 64 formed in front of the lead-detent 60 so as to be substantially parallel to an axis and to be fitted to an outer peripheral surface of the pushing jig A, and a second reduced-diameter portion 65 formed in front of the parallel hole 64 so as to be gradually reduced in diameter toward the front and to be pressed forward by the pushing jig A. And a lead core pressure contact portion 66 which comes into pressure contact with the outer peripheral surface of the lead core x inserted on the front side of the second reduced diameter portion 65.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a lead detent that is press-fitted into a mechanical pencil lead, a mechanical pencil lead equipped with this lead detent, and a method for manufacturing this mechanical pencil lead. [Background technology]

[0002] A lead detent made of an elastic material such as rubber is pressed into the tip of the lead for a mechanical pencil. This lead detent elastically presses against the outer surface of the lead that is fed out from the lead feeding mechanism, ensuring that the lead feeding operation of the lead feeding mechanism is carried out smoothly, and is sometimes called a lead breaker or the like (see, for example, Patent Document 1). 9(a) and 9(b) show how a conventional lead detent 130 is pressed into a tip 110 by a pressing jig 120 during the manufacturing process of a mechanical pencil lead. The pressing jig 120 is formed in the shape of a stepped shaft having a small diameter shaft portion 122 on the tip side of a large diameter shaft portion 121. The lead detent 130 has a bowl-shaped reduced diameter surface 131 that gradually reduces in diameter toward the front, and is pressed into the tip 110 as this reduced diameter surface 131 is pressed by the front end peripheral edge 121a of the large diameter shaft portion 121. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-196177 Summary of the Invention [Problem to be solved by the invention]

[0004] However, according to the above-mentioned conventional technology, the large diameter shaft portion 121 of the pushing jig 120 penetrates deep into the reduced diameter surface 131, which causes the outer surface of the lead detent 130 to expand in diameter, increasing the frictional resistance of the lead detent 130 against the inner surface of the tip 110, which may make it difficult to insert the lead detent 130 (see Figure 8(b)). In particular, when the front end peripheral edge 121a of the large diameter shaft portion 121 is worn down into a rounded chamfer due to repeated insertion operations, the above-mentioned problems become more pronounced. [Means for solving the problem]

[0005] In view of the above problems, one aspect of the present invention is provided with the following configuration. A lead detent that is pressed into the tip of a mechanical pencil from behind by a pressing jig, the lead detent having on its inner surface a first reduced diameter section that gradually reduces in diameter toward the front, a second reduced diameter section that is located forward of the first reduced diameter section and also gradually reduces in diameter toward the front, and a lead pressure contact section that is located forward of the second reduced diameter section and presses against the outer surface of the lead lead to be inserted, the second reduced diameter section having a larger reduced diameter angle than the first reduced diameter section, and is formed so as to be pressed forward by the pressing jig. [Effects of the Invention]

[0006] Since the present invention is configured as described above, the lead detent can be smoothly inserted into the tip. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a full cross-sectional view showing a lead for a mechanical pencil equipped with an example of a lead return stopper according to the present invention. FIG. [Figure 2] FIG. 10 is a half cross-sectional view showing a concentric detent. [Figure 3] FIG. 10 is a longitudinal cross-sectional view showing the state in which the concentric detent is attached to the pressing jig. [Figure 4] 10A and 10B are longitudinal cross-sectional views sequentially showing how a concentric detent is pressed into a tip by a pressing jig. [Figure 5] FIG. 10 is a vertical cross-sectional view showing the state in which the pressing jig is removed after the concentric detent is press-fitted into the tip. [Figure 6] A vertical cross-sectional view showing the connection between the tip and the lead detent. [Figure 7] FIG. 10 is a half cross-sectional view showing another example of a lead detent according to the present invention. [Figure 8] FIG. 10 is a half cross-sectional view showing another example of a lead detent according to the present invention. [Figure 9] 10A and 10B are longitudinal cross-sectional views sequentially showing how a conventional lead detent is pressed into a tip by a pressing jig. DETAILED DESCRIPTION OF THE INVENTION

[0008] Next, an embodiment of the present invention will be described in detail with reference to the drawings. First Embodiment FIG. 1 shows an example of a lead for a mechanical pencil equipped with a lead detent according to the present invention. This mechanical pencil lead 1 is equipped with a chuck 10 that clamps and releases the lead x with multiple claw portions 11, a clutch 20 that can be fitted into and detached from the multiple claw portions 11 in an annular shape, an advance / retract tube 30 that is fitted into and connected to a cylindrical portion 12 at the rear end of the clutch 20 in an annular shape, a support tube 40 that is formed in a cylindrical shape that is shorter than the advance / retract tube 30 and has the advance / retract tube 30 inserted into its rear end, a tip 50 that is detachably connected to the front end of the support tube 40, a lead return stop 60 supported within the tip 50, a compression coil spring 70 that is attached in an annular shape to the rear side of the advance / retract tube 30 with its front end abutting the rear end of the support tube 40, and a receiving member 80 that abuts the compressed compression coil spring 70 from the rear side and is fixed to the outer periphery of the advance / retract tube 30 so that it cannot be retracted.

[0009] This mechanical pencil lead 1 is connected to the front end of a cylindrical lead tank 90 and is stored in the barrel of a multi-function writing implement or mechanical pencil. When a rear end knocking portion (not shown) of this writing implement equipped with this mechanical pencil lead 1 is knocked, the receiving member 80, lead tank 90, chuck 10, etc. are reciprocated back and forth, and the lead lead x clamped in the chuck 10 is advanced forward.

[0010] More specifically, when the chuck 10 moves forward, the lead core x clamped by the chuck 10 moves forward and protrudes forward from the tip 50. Then, the chuck 10 that has moved forward is released from the clutch 20, thereby loosening the clamping force on the lead core x. Thereafter, the chuck 10 moves backward by the biasing force of the compression coil spring 70. During this retraction, the lead x is elastically gripped by the lead detent 60 and is therefore held in the advanced position without retracting.

[0011] The tip 50 is formed in a generally tapered cylindrical shape. The inside of the tip 50 is configured by a plurality of communicating through-holes with different outer diameters and shapes. 4, provided within the tip 50 are, in order from the front end, a substantially cylindrical lead insertion hole 51 that guides the lead lead x forward, a tapered lead lead guide hole 52 that gradually reduces in diameter toward the lead insertion hole 51, a cylindrical loose-fitting hole 53 that loosely fits into the front portion of the lead detent 60 behind the lead guide hole 52, a cylindrical press-fit hole 54 that is press-fit into the rear portion of the lead detent 60 behind the loose-fitting hole 53, and a tapered introduction hole 55 that guides the lead detent 60 into the press-fitting hole 54. Within the tip 50, the holes behind the introduction hole 55 function as a space that allows the jaws 11 of the chuck 10 to reciprocate back and forth.

[0012] A core detent 60 is press-fitted into the tip 50 having the above-mentioned configuration from the rear side by a pressing jig A. The pressing jig A is configured as a long, integral shaft consisting of a small diameter shaft portion a1 and a large diameter shaft portion a2 connected to the small diameter shaft portion a1 (see Figure 3). The pressing jig A is made of a hard metal material with good wear resistance.

[0013] The small diameter shaft portion a1 is formed in the shape of a cylindrical shaft having an outer diameter that is close to or in sliding contact with the inner circumferential surface of the lead insertion hole 51 of the tip 50.

[0014] The large diameter shaft portion a2 is formed in a cylindrical shape with a larger diameter than the small diameter shaft portion a1, and has approximately the same diameter as a parallel hole 64 of a core detent 60 described later. The large diameter shaft portion a2 has an edge-like corner a21 formed along the entire outer periphery of the front end thereof.

[0015] The lead detent 60 is formed in a generally cylindrical shape from an elastic material such as rubber or elastomer resin (see FIG. 2). The outer surface of this core return stopper 60 is composed of a tapered insertion portion 61 that fits loosely into the loose-fitting hole 53 of the tip 50, and a press-fit outer diameter portion 62 that is located behind the tapered insertion portion 61 and is press-fit into the press-fit hole 54 of the tip 50.

[0016] The tapered insertion portion 61 is formed so as to taper forward, and when fitted into the loose-fitting hole 53 of the tip 50, a space is secured between the tapered insertion portion 61 and the inner surface of the loose-fitting hole 53, which gradually widens as it goes forward (see Figure 4(b)).

[0017] The press-fit outer diameter portion 62 has an outer circumferential surface that is substantially cylindrical. The press-fit outer diameter portion 62 has an outer diameter that is slightly larger than the inner diameter of the press-fit hole 54 so that the press-fit outer diameter portion 62 can be elastically contracted and press-fitted into the press-fit hole 54 of the tip 50. The front end surface of this press-fit outer diameter portion 62 is a stepped portion formed by expanding the diameter of the rear end portion of the tapered insertion portion 61, and this stepped portion 62a is formed so as to overlap with the stepped portion 54a between the loose-fit hole 53 and the press-fit hole 54 in the tip 50.

[0018] According to a preferred example of this embodiment, in the lead detent 60, the weight of the portion having the tapered insertion portion 61 is set to be greater than the weight of the portion having the press-fit outer diameter portion 62. Specifically, the length L1 in the front-to-rear direction of the tapered insertion portion 61 is set to be approximately 1.3 times the length L2 in the front-to-rear direction of the press-fit outer diameter portion 62 (see FIG. 2). According to this configuration, when the lead detent 60 is transported, it can be stabilized by facing the tapered insertion portion 61 downward and hooking the step portion 62a onto the parts feeder.

[0019] As shown in Figure 2, the inner surface of the lead return stopper 60 has a first reduced diameter portion 63 that gradually reduces in diameter from the rear end of the lead return stopper 60 toward the front, a parallel hole 64 located forward of the first reduced diameter portion 63, a second reduced diameter portion 65 that gradually reduces in diameter toward the front in front of the parallel hole 64, a lead core pressure contact portion 66 that loosely presses against the outer surface of the lead core x to be inserted forward of this second reduced diameter portion 65, and a retracted lead introduction portion 67 that gradually expands in diameter toward the front in front of the lead core pressure contact portion 66.

[0020] The first reduced diameter portion 63 is formed in a cone shape tapering forward so as to smoothly guide the lead core x forward.

[0021] The parallel hole 64 is a through hole located between the first reduced diameter portion 63 and the second reduced diameter portion 65 and is substantially parallel to the axis of the core detent 60 . The parallel hole 64 has an inner diameter that is approximately the same as the outer diameter of the large-diameter shaft portion a2 so as to fit into the large-diameter shaft portion a2 of the pressing jig A.

[0022] The second reduced diameter portion 65 is formed in a cone shape tapering forward so as to smoothly guide the lead core x to the lead core pressure contact portion 66 in the front.

[0023] The second reduced diameter portion 65 has a reduced diameter angle α1 that is larger than the reduced diameter angle α2 of the first reduced diameter portion, and is formed so as to be pressed forward by the large diameter shaft portion a2 of the pressing jig A.

[0024] The reduced diameter angle α1 is the angle of the inner surface of the first reduced diameter portion 63 relative to the axis of the core detent 60, and in the illustrated example, is also the angle of the inner surface of the first reduced diameter portion 63 relative to the inner surface of the parallel hole 64. This diameter reduction angle α1 is set to, for example, about 10°.

[0025] The reduced diameter angle α2 is the angle of the inner surface of the second reduced diameter portion 65 relative to the axis of the lead detent 60, and in the illustrated example, is also the angle of the inner surface of the second reduced diameter portion 65 relative to the inner surface of the lead lead pressure contact portion 66. This diameter reduction angle α2 is adjusted appropriately so that the lead core x can be easily pressed by the large diameter shaft portion a2 of the advancing pressing jig A and can be smoothly guided forward. This diameter reduction angle α2 is set within the range of 15 to 45°, and more preferably, is set to an angle of approximately 30°.

[0026] The lead core pressure contact portion 66 is a cylindrical hole parallel to the axis of the lead detent 60. This lead core pressure contact portion 66 has an inner diameter slightly smaller than the outer diameter of the lead core x, and is loosely pressed against the outer peripheral surface of the lead core x so as not to hinder the forward movement of the lead core x.

[0027] The retraction-core introduction portion 67 is a generally trumpet-shaped hole that guides the lead core x rearward when the lead core x is inserted from the front.

[0028] <Features of the connection between the tip and support tube> As shown in FIG. 6, at the connection portion between the tip 50 and the support tube 40, an overlapping portion 50b having a predetermined width w and no thread portion is provided behind the thread fitting portion 50a. The threaded engagement portion 50a is a portion where the female threaded portion 56 of the tip 50 and the male threaded portion 41 of the support tube 40 are threadedly engaged. The overlapping portion 50b is located behind the female thread portion 56 and the male thread portion 41, and is formed by overlapping the peripheral wall portion of the tip 50 that does not have a thread portion with the peripheral wall portion of the support tube 40 that does not have a thread portion. The length w of this overlapping portion 50b and the thickness of each of the peripheral walls are appropriately set so that when an excessive bending force is applied to the connecting portion between the tip 50 and the support tube 40, this bending force can be withstood.

[0029] According to the overlapping portion 50b having the above-described configuration, the strength of the connecting portion between the tip 50 and the support tube 40 can be effectively improved. That is, if the overlapping portion 50b were omitted, there would be a risk of breakage occurring at the rear end of the thread fitting portion 50a if a bending force were applied to the connection portion between the tip 50 and the support tube 40. However, such breakage can be effectively prevented by the above-described configuration having the overlapping portion 50b.

[0030] <Features of the manufacturing method> Next, the characteristics of the manufacturing method for inserting the lead detent 60 into the tip 50 of the mechanical pencil core 1 having the above-described configuration will be described in detail.

[0031] First, as shown in FIG. 3, the lead detent 60 is fitted into the pushing jig A from the front side in an annular shape. The core detent 60 is configured such that the rear end of the second reduced diameter portion 65 is pressed against the corner a21 at the front end of the large diameter shaft portion a2 of the pushing jig A, and the inner surface of the parallel hole 64 is fitted into the outer surface of the large diameter shaft portion a2 of the pushing jig A.

[0032] Next, as shown in Figures 4(a) and (b), the pushing jig A equipped with the core detent 60 is inserted into the tip 50 from the rear, and the tapered insertion portion 61 is inserted into the loose-fit hole 53, and the press-fit outer diameter portion 62 is pressed into the press-fit hole 54 of the tip 50. This insertion operation causes the step 62a at the front end of the press-fit outer diameter portion 62 to abut against the step 54a at the front end of the press-fit hole 54, and the lead detent 60 is held against the tip 50 so that it cannot be easily pulled out.

[0033] Therefore, according to the mechanical pencil lead 1 and its manufacturing method configured as described above, when the pushing jig A is used to push the lead detent 60 into the tip 50, the corner a21 at the front end of the large diameter shank a2 of the pushing jig A abuts from behind against the rear end of the second reduced diameter portion 65 of the lead detent 60. In other words, the advancing corner a21 gets caught on the rear end of the second reduced diameter portion 65. As the pushing jig A advances, the lead detent 60 advances smoothly until it reaches a predetermined position. This prevents the large diameter shaft portion 121 of the pushing jig 120 from penetrating deep into the reduced diameter surface 131, causing the outer surface of the core detent 130 to expand in diameter, making it difficult to insert the core detent 130, as in the conventional technology shown in Figure 8.

[0034] Furthermore, when the lead return stopper 60 is attached to the pushing jig A, the parallel hole 64 of the lead return stopper 60 overlaps with the outer surface of the large diameter shaft portion a2 of the pushing jig A and comes into almost close contact, preventing the lead return stopper 60 from tilting relative to the pushing jig A and allowing the lead return stopper 60 to be inserted smoothly.

[0035] Second Embodiment According to the above embodiment, the lead detent 60 is provided with a parallel hole 64 as a particularly preferred example, but alternatively, a lead detent 60' as shown in FIG. 7 may be used. The lead detent 60 ′ is the same as the lead detent 60 as described above, except that the parallel hole 64 is omitted and the front end of the first reduced diameter portion 63 is directly connected to the rear end of the second reduced diameter portion 65 .

[0036] According to this lead detent 60', in substantially the same manner as the lead detent 60 described above, when the pushing jig A is used to push the lead detent 60' into the tip 50, the corner a21 at the front end of the large diameter shaft portion a2 of the pushing jig A abuts against the rear end of the second reduced diameter portion 65 of the lead detent 60' from behind, and the lead detent 60' advances as the pushing jig A advances. Therefore, the lead detent 60' can be smoothly inserted into the tip 50 to its designated position.

[0037] <Third embodiment> The lead detent 60″ shown in FIG. 8 is a detent in which the diameter reduction angles α1 and α2 are changed from those of the lead detent 60 described above, and like the lead detent 60 described above, it is pressed into the tip 50 of a mechanical pencil from behind by a pressing jig A.

[0038] The lead detent 60″ has, integrally on its inner peripheral surface, a first reduced diameter portion 63 whose diameter gradually decreases toward the front, a parallel hole 64 formed in front of the first reduced diameter portion 63, substantially parallel to the axis, and adapted to fit into the outer peripheral surface of the large diameter shaft portion a2 of the pushing-in jig A, a second reduced diameter portion 65 formed in front of the parallel hole 64, whose diameter gradually decreases toward the front, and adapted to be pressed forward by a corner portion a21 (see FIG. 4 ) of the large diameter shaft portion a2 of the pushing-in jig A, and a lead lead pressure contact portion 66 which is in pressure contact with the outer peripheral surface of the lead lead x to be inserted, in front of the second reduced diameter portion 65.

[0039] In this core detent 60'', the diameter reduction angle α1 and the diameter reduction angle α2 are approximately the same angle, and according to an example shown in FIG. 8, the diameter reduction angle α1 is approximately 18° and the diameter reduction angle α2 is approximately 20°.

[0040] Therefore, according to the lead detent 60" shown in FIG. 8, when it is inserted into the tip 50 by the pushing jig A, the inner peripheral surface of the parallel hole 64 overlaps and comes into nearly tight contact with the outer peripheral surface of the large diameter shaft portion a2 of the pushing jig A. This makes it possible to prevent the lead detent 60" from tilting or rattling with respect to the pushing jig A. During this insertion operation, in much the same way as in the case of the lead detent 60, the corner a21 at the front end of the large diameter shaft portion a2 of the pushing jig A abuts against the second reduced diameter portion 65 of the lead detent 60″ from behind (see FIG. 4), and as the pushing jig A advances, the lead detent 60″ advances smoothly until it reaches the specified position.

[0041] <Other variations> According to the above embodiment, the second reduced diameter portion 65 is formed by an inclined surface having a linear longitudinal cross section that reduces in diameter toward the front (see FIG. 2). However, other examples of the second reduced diameter portion 65 include an inclined surface having a concave curved longitudinal cross section that reduces in diameter toward the front, and an inclined surface having a convex curved longitudinal cross section that reduces in diameter toward the front. When the second reduced diameter portion 65 has an inclined surface with a concave curved longitudinal section, the lead core inserted from the rear can be more easily guided. Furthermore, when the second reduced diameter portion 65 is formed as an inclined surface having a convex curved longitudinal section, the large diameter shaft portion a2 of the pressing jig A can be made to be more easily engaged.

[0042] According to the above embodiment, as a preferred example, the corner a21 of the pushing jig A is pressed against the rear end of the second reduced diameter portion 65, but as another example, it is also possible to configure the corner a21 of the pushing jig A to be pressed against a mid-inclined position of the second reduced diameter portion 65.

[0043] In the above embodiment, the diameter reduction angle α2 is larger than the diameter reduction angle α1 (see FIGS. 2 and 7), and the diameter reduction angle α1 and the diameter reduction angle α2 are substantially the same (see FIG. 8). However, as another example, the diameter reduction angle α2 can be smaller than the diameter reduction angle α1 (not shown). In this other example, a parallel hole 64 is preferably provided between the first diameter reduction portion 63 and the lead-core pressure contact portion 66.

[0044] Furthermore, the present invention is not limited to the specific configurations described above, and can be modified as appropriate within the scope of the present invention.

[0045] <Summary> As described above, the above embodiments disclose the following inventions. (1) A lead detent that is pressed into the tip of a mechanical pencil from behind by a pressing jig, characterized in that the inner surface has a first reduced diameter section that gradually reduces in diameter toward the front, a second reduced diameter section that is located forward of the first reduced diameter section and gradually reduces in diameter toward the front, and a lead pressure contact section that is located forward of the second reduced diameter section and presses against the outer surface of the lead lead to be inserted, the second reduced diameter section having a larger reduced diameter angle than the first reduced diameter section and is formed so as to be pressed forward by the pressing jig (see Figures 2 to 5 and 7). (2) The lead detent according to (1) (see FIG. 2) is characterized in that a parallel hole that is approximately parallel to the axis is provided between the first reduced diameter portion and the second reduced diameter portion. (3) This lead detent is pressed into the tip of a mechanical pencil from behind by a pressing jig, and is characterized in that it has on its inner surface a first reduced diameter section that gradually reduces in diameter towards the front, a parallel hole formed in front of this first reduced diameter section and approximately parallel to the shaft core so as to fit into the outer surface of the pressing jig, a second reduced diameter section formed in front of this parallel hole that gradually reduces in diameter towards the front and is pressed forward by the pressing jig, and a lead lead pressure contact section that presses against the outer surface of the lead lead to be inserted in front of the second reduced diameter section (see Figures 2 to 5 and 8). (4) The lead detent according to (3) (see FIG. 8) is characterized in that the diameter reduction angle of the first diameter reduction portion and the diameter reduction angle of the second diameter reduction portion are substantially the same. (5) A lead for a mechanical pencil (see FIG. 1) having a lead detent according to any one of (1) to (4) provided inside the tip. (6) The lead for a mechanical pencil described in (5) (see Figure 6) is provided with a support tube connected to the rear end of the tip, and the connection between the tip and the support tube is provided with a threaded fitting portion and an overlapping portion behind the threaded fitting portion, and the overlapping portion is formed by overlapping the non-threaded portion of the tip and the non-threaded portion of the support tube. (7) A method for manufacturing a lead for a mechanical pencil according to (5) or (6), characterized in that it includes a step of pressing the pushing jig against the second reduced diameter portion and pressing the lead detent into the tip (see Figure 4). [Explanation of symbols]

[0046] 1 Mechanical pencil lead 10. Chuck 20 Clutch 30 Advance / retreat pipe 40 Support tube 50 First Gold 50a screw fitting 50b Overlapping part 51 Core insertion hole 52 Lead core guide hole 53 Loose fit hole 54 Press-fit hole 54a Stepped section 55 Inlet hole 60,60',60" Core detent 61 Tapered insertion part 62 Press-fit outer diameter 62a Stepped section 63 First narrowing section 64 parallel holes 65 Second narrowing section 66 Lead core pressure welding part 67 Retraction core introduction part A Push-in jig a1 Small diameter shaft a2 Large diameter shaft a21 corner x lead core α1 Diameter reduction angle α2 Diameter reduction angle

Claims

1. In a lead detent that is pressed into the tip of a mechanical pencil from behind by a pressing jig, The inner peripheral surface has a first reduced diameter portion that gradually reduces in diameter toward the front, a second reduced diameter portion that gradually reduces in diameter toward the front on the front side of the first reduced diameter portion, and a lead core press-contact portion that presses against the outer peripheral surface of the lead core to be inserted on the front side of the second reduced diameter portion, A lead detent, characterized in that the second reduced diameter portion has a reduced diameter angle greater than the reduced diameter angle of the first reduced diameter portion and is formed so as to be pressed forward by the pushing jig.

2. 2. The lead detent according to claim 1, wherein a parallel hole extending substantially parallel to the axis is provided between the first reduced diameter portion and the second reduced diameter portion.

3. In a lead detent that is pressed into the tip of a mechanical pencil from behind by a pressing jig, A lead backstop characterized in that the inner surface has a first reduced diameter section that gradually reduces in diameter toward the front, a parallel hole formed in front of this first reduced diameter section and approximately parallel to the axis so as to fit into the outer surface of the pushing jig, a second reduced diameter section formed in front of this parallel hole that gradually reduces in diameter toward the front and is pressed forward by the pushing jig, and a lead lead pressure contact section that presses against the outer surface of the lead lead to be inserted in front of this second reduced diameter section.

4. 4. The lead detent according to claim 3, wherein the first reduced diameter portion and the second reduced diameter portion have substantially the same reduced diameter angle.

5. A lead for a mechanical pencil, the lead detent according to any one of claims 1 to 4 being provided inside a tip.

6. a support tube connected to the rear end side of the tip, a thread fitting portion and an overlapping portion located rearward of the thread fitting portion are provided at a connection portion between the tip and the support tube, 6. The lead for a mechanical pencil according to claim 5, wherein the overlapping portion is formed by overlapping a portion of the tip that does not have a threaded portion with a portion of the support tube that does not have a threaded portion.

7. 6. A method for manufacturing a core for a mechanical pencil according to claim 5, A method for manufacturing a lead for a mechanical pencil, comprising the steps of pressing the pushing jig against the second reduced diameter portion and pressing the lead detent into the tip.

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