Method for manufacturing golf shafts and golf shaft sets

Abstract

This product provides a golf shaft set that can suppress the decrease in rigidity of the golf shaft caused by an increase in overall length. [Solution] The golf shaft set comprises multiple golf shafts 1 of different lengths, each having a multi-stage stepped section 9 between the axial tip 3 and base 5, where the outer diameter gradually increases toward the base 5. The ratio of the stiffness Q2 of the longest golf shaft 1(12) to the stiffness QW of the shortest golf shaft 1(1W) is 90% or more, and the stiffness is the stiffness over the entire common length range of the shortest golf shaft 1(1W) and the longest golf shaft 1(12).

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing golf shafts of different overall lengths having multi-step stepped portions and a golf shaft set. [Background Art]

[0002] As a golf shaft, for example, as disclosed in Patent Document 1, there is known a golf shaft that has multi-step stepped portions between an axial distal end portion (tip-side end portion) and a proximal end portion (butt-side end portion), the outer diameter of which gradually increases toward the proximal end portion.

[0003] In a golf shaft having such stepped portions, club numbers corresponding to different overall lengths are set by varying the length of the distal end portion relative to the stepped portions.

[0004] However, in such a golf shaft, as the overall length increases, the stepped portions shift toward the proximal end side. For this reason, a golf shaft with a longer overall length has lower rigidity at a location the same distance from the distal end compared to a golf shaft with a shorter overall length.

[0005] Therefore, a golf shaft with a longer overall length has the problem that a reduction in rigidity occurs, the amount of bending increases, and impact deviation tends to become large. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Unexamined Patent Publication No. Hei 3-063076 [Brief Summary of the Invention] [Problem to be Solved by the Invention]

[0007] The problem to be solved is that the longer the overall length of a golf shaft is, the more the rigidity of the golf shaft decreases. [Means for Solving the Problem]

[0008] The present invention provides a set of golf shafts of multiple numbers with different overall lengths, each having a multi-stage stepped portion between the axial tip and base portion, where the outer diameter gradually increases toward the base portion, and the wall thickness of the tip portion is relatively thicker. The multiple golf shafts of multiple numbers have different overall lengths due to differences in the length of at least a portion of the stepped portion, and the ratio of the stiffness of the longest golf shaft to the stiffness of the shortest golf shaft is 90% or more, and the stiffness is the stiffness over the entire common length range between the shortest golf shaft and the longest golf shaft, and the common length range is a constant range in the multiple golf shafts from the tip to the position on the base portion.

[0009] Furthermore, the present invention has a multi-stage stepped portion between the axial tip and base end, where the outer diameter gradually increases toward the base end, and the tip has a relatively thicker wall thickness, resulting in a different overall length. Multiple numbers A method for manufacturing a golf shaft is provided, wherein the total length of the golf shaft is set by adjusting the length of at least a part of the step portion, the ratio of the stiffness of the longest golf shaft to the stiffness of the shortest golf shaft is 90% or more, the stiffness is the stiffness over the entire common length range between the shortest golf shaft and the longest golf shaft, and the common length range is a constant range in the length from the tip to the position on the base end of the golf shafts of the multiple club numbers. [Effects of the Invention]

[0010] According to the present invention, it is possible to suppress the decrease in rigidity of the golf shaft caused by an increase in overall length. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram showing the external appearance of a golf shaft according to Embodiment 1 of the present invention. [Figure 2] Figure 2 is an enlarged view showing the tip and a portion of the step section of the golf shaft shown in Figure 1. [Figure 3] Figure 3 is a schematic diagram comparing the longest and shortest golf shafts in the golf shaft set according to Example 1. [Figure 4] Figure 4 is a table showing the lengths of the golf shafts in the golf shaft set shown in Figure 3. [Figure 5] Figure 5 is a graph showing the stiffness distribution of the golf shaft set shown in Figure 3. [Figure 6] Figure 6 is a graph showing the stiffness distribution of the longest and shortest golf shafts in the golf shaft set shown in Figure 3. [Figure 7] Figure 7 is a graph showing the stiffness distribution in a golf shaft set related to a comparative example. [Figure 8] Figure 8 is a graph showing the stiffness distribution of the longest and shortest golf shafts in the comparative example golf shaft set. [Figure 9] Figure 9 is a schematic diagram comparing the longest and shortest golf shafts in a comparative example golf shaft set. [Figure 10] Figure 10 is a table showing the ratio of stiffness of the other golf shafts in a set to the shortest golf shaft, comparing Example 1 with a comparative example. [Figure 11] Figure 11 is a schematic diagram showing the manufacturing method of a golf shaft according to Example 1. [Figure 12] Figure 12 is a schematic diagram comparing the longest and shortest golf shafts in a golf shaft set according to Embodiment 2 of the present invention. [Figure 13] Figure 13 is a schematic diagram comparing the longest and shortest golf shafts in a golf shaft set according to Embodiment 3 of the present invention. MODE FOR CARRYING OUT THE INVENTION

[0012] A golf shaft set of one embodiment has, between an axially distal tip portion 3 and a base end portion 5, a multi-stage step portion 9 whose outer diameter gradually increases toward the base end portion 5, and comprises golf shafts 1 of a plurality of club numbers having different overall lengths.

[0013] In such a golf shaft set, the ratio of the stiffness Q2 of the longest golf shaft 1 (12) to the stiffness QW of the shortest golf shaft 1 (1W) is 90% or more. The stiffness QW and Q2 are the stiffness over the entire common length range of the shortest golf shaft 1 (1W) and the longest golf shaft 1 (12).

[0014] Furthermore, in the golf shaft set, the length of the tip portion 3 is constant from the longest golf shaft 1 (12) to the shortest golf shaft 1 (1W), and the overall lengths of the golf shafts 1 of the plurality of club numbers differ depending on a partial length of the step portion 9 and the base end portion 5.

[0015] Furthermore, a method for manufacturing a golf shaft according to one embodiment manufactures golf shafts 1 having different overall lengths, each of which has a multi-stage step portion 9 between an axially distal tip portion 3 and a base end portion 5.

[0016] In this method for manufacturing a golf shaft, the overall length of the golf shaft 1 is set by adjusting at least a partial length of the step portion 9 and the base end portion 5, and the rate of decrease in stiffness caused by increasing the overall length of the golf shaft 1 is made smaller than that of a reference golf shaft 1A.

[0017] In one embodiment, the overall length of the golf shaft 1 may be set by keeping the length of the tip portion 3 constant and adjusting a partial length of the step portion 9 and the base end portion 5.

[0018] In another embodiment, the total length of the golf shaft 1 may be set by adjusting the length of the tip portion 3 along with the length of a portion of the step portion 9 and the base portion 5.

[0019] In the manufacturing method of the golf shaft 1, it is preferable that the ratio of the stiffness Q2 of the longest golf shaft 1 (12) to the stiffness QW of the shortest golf shaft 1 (1W) is 90% or more. [Examples]

[0020] [Golf shaft] Figure 1 is a schematic diagram showing the external appearance of a golf shaft according to Embodiment 1 of the present invention. Figure 2 is an enlarged view showing a part of the tip and step portion of the golf shaft of Figure 1.

[0021] The golf shaft 1 is formed in a hollow cylindrical shape from a metal, particularly steel. The golf shaft 1 has an outer circumferential surface whose outer diameter gradually increases from the tip to the butt in the axial direction, and comprises a tip portion 3, a butt portion 5, and an intermediate portion 7.

[0022] The tip portion 3 is the part to which the head is attached, and the base portion 5 is the part to which the grip is attached. The intermediate portion 7 is located between the tip portion 3 and the base portion 5, and in this embodiment, it is composed of a multi-stage step portion 9.

[0023] In this embodiment, the tip portion 3 is located further forward than the step portion 9. This tip portion 3 is composed of, for example, a first tapered portion 3a, a second tapered portion 3b, a straight portion 3c, and a third tapered portion 3d continuously from the tip. However, the tip portion 3 can adopt various configurations; for example, it may be entirely a straight portion or have one or more tapered portions.

[0024] The first tapered portion 3a and the second tapered portion 3b have tapered outer surfaces that are inclined so that the outer diameter gradually increases from the tip side. The taper ratio of the second tapered portion 3b is greater than that of the first tapered portion 3a, and the taper ratios of the first tapered portion 3a and the second tapered portion 3b are smaller than that of the third tapered portion 3d.

[0025] The straight section 3c has an outer circumferential surface with a constant outer diameter. The third tapered section 3d is the part that transitions to the stepped section 9 and has a tapered outer circumferential surface that slopes so that the outer diameter gradually increases from the tip side. The third tapered section 3d has the same taper ratio as the tapered section 9b of the stepped section 9, which will be described later, and for example, the taper ratio is set to 0.03 or higher.

[0026] The intermediate section 7, which is the step section 9, is the portion that is axially adjacent to the straight section 3c of the tip section 3 via a tapered section (the third tapered section 3d in this embodiment). If the tip section 3 does not have a straight section 3c, the step section 9 will begin from the first straight section 9a located on the axial tip side.

[0027] The step section 9 is composed of multiple straight sections 9a with different outer diameters and tapered sections 9b located between adjacent straight sections 9a. Within each straight section 9a of the step section 9, the outer diameter of the outer surface is kept constant. In such a step section 9, the characteristics can be varied by adjusting the number and length of the straight sections 9a.

[0028] The tapered portion 9b of the step portion 9 is a portion that absorbs the difference in outer diameter of the adjacent straight portion 9a in the axial direction, and has a tapered outer surface that is inclined so that the outer diameter gradually increases from the tip side. These tapered portions 9b have the same taper ratio as the third tapered portion 3d of the tip portion 3 as described above. Note that the tapered portions 9b of the step portion 9 may have different taper ratios from each other, and may also have a greater taper ratio than the third tapered portion 3d.

[0029] The base end portion 5 consists of a straight portion 5a adjacent to the last tapered portion 9b of the step portion 9, and the outer diameter of the outer circumferential surface is formed to be constant.

[0030] In this golf shaft 1, the length corresponding to the club number is set by adjusting the length of at least a portion of the step portion 9 and the base portion 5. In this embodiment, the length of the tip portion 3 is kept constant, and the length of the base portion 5, which is a portion of the step portion 9 and the base portion 5, is adjusted to set the length of the golf shaft 1 corresponding to the club number in the golf shaft set.

[0031] [Golf shaft set] Figure 3 is a schematic diagram comparing the longest and shortest golf shafts in the golf shaft set according to Example 1. Figure 4 is a table showing the lengths of the golf shafts in the golf shaft set according to Example 1.

[0032] In Figure 3, the longest golf shaft 1 is for a 2-iron and has a total length of, for example, 939 mm. The shortest golf shaft 1 is for a wedge (W-type) and has a total length of, for example, 838 mm. These golf shafts 1 have the same length for the tip section 3 and the step section 9, but differ in the length of the base section 5. The longest golf shaft 1 (12) has a total length of 939 mm to 1041 mm, and the shortest golf shaft 1 (1W) has a total length of 838 mm to 940 mm. The longest golf shaft 1 is the longest in the same golf set, and the shortest golf shaft 1 is the shortest in the same golf set.

[0033] Thus, in this embodiment of the golf shaft set, the length of the tip section 3 is kept constant, and the total length of the different golf shafts 1, from No. 2 to No. W, is determined by the length of the base section 5, which is a part of the length of the step section 9 and the base section 5, as shown in Figure 4.

[0034] Specifically, in this embodiment, the length of the tip section 3 and the step section 9 are kept constant for the shortest golf shaft 1, and the total length of the other club shafts 1 is determined by the length of the base section 5. The weights of the multiple club shafts 1 in this embodiment are approximately the same.

[0035] In such a set of golf shafts, the ratio of the stiffness of the longest golf shaft 1 to the stiffness of the shortest golf shaft 1 (stiffness ratio) is 90% or more. That is, if the stiffness of the longest golf shaft 1 is Q2 and the stiffness of the shortest golf shaft 1 is QW, then Q2 / QW ≥ 90%. Stiffness refers to bending stiffness.

[0036] The stiffness referred to here is the stiffness over the entire common length range between the shortest golf shaft 1(1W) and the longest golf shaft 1(12). In this embodiment, this stiffness is defined as the area in the stiffness distribution, as will be described later. Furthermore, the common length range in this embodiment is the range where the lengths from the tip of the golf shaft 1 are the same, with the tip as the starting point and preferably ending at a position on the base end 5 where the stiffness distribution changes constantly for both the shortest golf shaft 1(1W) and the longest golf shaft 1(12). However, the end point of the common length range can be appropriately set to the end point of the step portion 9 of the longest golf shaft 1(12).

[0037] Figure 5 is a graph showing the stiffness distribution in the golf shaft set according to Example 1. Figure 6 is a graph showing the stiffness distribution of the longest and shortest golf shafts in the golf shaft set of Figure 5. Figure 7 is a graph showing the stiffness distribution in the golf shaft set according to the comparative example. Figure 8 is a graph showing the stiffness distribution of the longest and shortest golf shafts in the golf shaft set according to the comparative example. Figure 9 is a schematic diagram comparing the longest and shortest golf shafts in the golf shaft set according to the comparative example. Figure 10 is a table showing the stiffness ratio of the other club shafts relative to the shortest golf shaft in the golf shaft set, comparing Example 1 and the comparative example.

[0038] In the golf shaft set of this embodiment shown in Figures 5 and 6, the stiffness distribution of the longest golf shaft 1(12) and the stiffness distribution of the shortest golf shaft 1(1W) are close in length compared to the comparative example golf shaft set shown in Figures 7 and 8.

[0039] In the comparative example golf shaft set, as shown in Figure 9, the lengths of the step section 9A and the base end 5A are kept constant, and the total length of each club number is determined by the length of the tip section 3A, resulting in a standard golf shaft 1A. The golf shafts 1 and 1A (1W and 1WA), which have the shortest total length in both this embodiment and the comparative example, have the same configuration.

[0040] In this embodiment of the golf shaft set, as shown in Figure 10, when the stiffness Q2 of the longest golf shaft 1 and the stiffness QW of the shortest golf shaft 1 are converted to an area in the stiffness distribution and compared, Q2 / QW is 91.4%, and Q2 / QW ≥ 90%.

[0041] Furthermore, if the weight increases with the overall length of the golf shaft 1, Q2 / QW will be larger. Conversely, if the weight decreases with the overall length of the golf shaft 1, Q2 / QW will be smaller, but Q2 / QW ≥ 90%.

[0042] Here, the stiffness (area) in the stiffness distribution of Figure 10 is the area between the line segment of the stiffness distribution and the horizontal axis for a length range where the length from the tip to the base of the golf shaft 1 is constant, specifically 838 mm, as shown in Figure 6. However, the dimensions of the length range are just an example and can be set as appropriate. In Figure 6, the horizontal axis represents the length from the tip, and the vertical axis represents the bending stiffness.

[0043] In the comparative example golf shaft set, when the stiffness Q2' of the longest golf shaft 1A (12A) and the stiffness QW of the shortest golf shaft 1A (1WA) are converted to an area in the stiffness distribution and compared, the result is 82.5%, and Q2' / QW ≤ 90%.

[0044] Therefore, in the golf shaft set of this embodiment, even the golf shaft 1 (12), which has a longer overall length, can be made to have a similar amount of flex as the golf shaft 1A (1WA), which has a shorter overall length. In other words, in this embodiment, the rate of decrease in rigidity due to the lengthening of the overall length of the golf shaft 1 is made smaller than that of the standard golf shaft 1 (comparative example golf shaft 1A), and the wobble at impact can be reduced.

[0045] In particular, if Q2 / QW ≥ 90%, the impact deviation can be reduced regardless of which club number golf shaft 1 is used.

[0046] Furthermore, the golf shaft 1 of this embodiment can suppress the decrease in rigidity from the tip portion 3 to the tip-side region of the adjacent step portion 9, thereby improving stability. Moreover, since the suppression of the decrease in rigidity in the golf shaft 1 of this embodiment does not involve an increase in weight, the decrease in head speed can also be suppressed.

[0047] [How to manufacture golf shafts] Figure 11 is a schematic diagram showing the manufacturing method of a golf shaft according to Example 1.

[0048] In the manufacturing method of the golf shaft 1 of the embodiment, the raw tube 11, which has undergone processes such as thickness variation processing, is subjected to stepping processing as shown in Figure 11.

[0049] In variable thickness processing, a cylindrical tube 11 with a constant outer diameter has sections with relatively thicker and thinner walls due to differences in the inner diameter. This variable thickness processing makes the wall thickness of the tip section 3 of a golf shaft 1 relatively thicker. Variable thickness processing can be performed as needed; for example, the wall thickness can be made relatively thicker in the middle section 7 and relatively thinner on both sides.

[0050] Stepping is performed using a die 13 on the base tube 11 from the tip portion 3 toward the base end, forming a step portion 9 and a base portion 5. In this case, as shown in Figure 3, the same stepping process is performed on golf shafts 1 of different numbers, with the length of the tip portion 3 kept constant, to form the same step portion 9. The base portion 5 is set to a different length for each number by using base tubes 11 of different lengths for each number, as a result of forming the step portion 9 on the tip portion 3 and the intermediate portion 7. It is also possible to shorten the base portion 5 by cutting it after stepping on a base tube 11 of the same length. Therefore, in this embodiment, it is possible to easily manufacture golf shafts 1 of different numbers by using the same stepping process.

[0051] Swaging is performed to form the first tapered portion 3a and the second tapered portion 3b of the tip portion 3 of the golf shaft 1 shown in Figure 2. Alternatively, only the first tapered portion 3a may be swaged. Furthermore, swaging may be omitted.

[0052] The golf shaft 1 thus formed can reduce the rate of decrease in stiffness due to the increase in overall length compared to the standard (comparative example) golf shaft 1A. Furthermore, a golf shaft set using such a golf shaft 1 can achieve a ratio of 90% or more of the stiffness Q2 of the longest golf shaft 1 (12) to the stiffness QW of the shortest golf shaft 1 (1W).

[0053] As described above, the manufacturing method of the golf shaft 1 in this embodiment produces a golf shaft 1 of different lengths having a multi-stage stepped portion 9 between the axial tip portion 3 and the base portion 5, the outer diameter of which gradually increases toward the base portion 5.

[0054] In this manufacturing method for the golf shaft 1, the length of the tip section 3 is kept constant, and the length of the base section 5, which is part of the step section 9 and base section 5, is adjusted to set the overall length of the golf shaft 1. This reduces the rate of decrease in rigidity due to increasing the overall length of the golf shaft 1 compared to the standard golf shaft 1A.

[0055] Therefore, in this embodiment, the decrease in rigidity of the golf shaft 1 due to the increased overall length can be suppressed, and even with a long golf shaft 1, the impact wobble can be reduced.

[0056] Furthermore, in the golf shaft set of this embodiment, the ratio of the stiffness Q2 of the longest golf shaft 1 to the stiffness QW of the shortest golf shaft 1 is 90% or more.

[0057] Therefore, with a golf shaft set, regardless of which club number's golf shaft 1 is used, the deviation at impact can be minimized. [Examples]

[0058] Figure 12 is a schematic diagram comparing the longest and shortest golf shafts in a golf shaft set according to Embodiment 2 of the present invention. Embodiment 2 shares the same basic configuration as Embodiment 1, and the same reference numerals are used for corresponding components to omit redundant explanations.

[0059] In Figure 12, the longest golf shaft 1 is for a 2-iron, and the shortest golf shaft 1 is for a wedge (W-type). These golf shafts 1 have the same length at the tip 3 and base 5, but the lengths of the intermediate step section 9 (7) differ.

[0060] In other words, in this embodiment, the length of the tip portion 3 is kept constant, and the total length of the golf shaft 1 is determined by adjusting the length of the step portion 9, which is a part of the base portion 5.

[0061] As a result, in this embodiment as well, similar to Embodiment 1, the rate of reduction in rigidity due to increasing the overall length of the golf shaft 1 can be made smaller than that of the standard golf shaft 1A.

[0062] Therefore, in this embodiment, as in Embodiment 1, the stiffness distribution of the longest golf shaft 1 and the stiffness distribution of the shortest golf shaft 1 can be made close to those of the comparative example golf shaft set in Figures 7 and 8.

[0063] In this embodiment of the golf shaft set, similar to Embodiment 1, when the stiffness Q2 of the longest golf shaft 1(12) and the stiffness QW of the shortest golf shaft 1(1W) are converted to an area in the stiffness distribution and compared, Q2 / QW ≥ 90%.

[0064] As a result, in this embodiment of the golf shaft set, the rate of reduction in rigidity due to the lengthening of the overall length of the golf shaft 1 is made smaller than that of the standard golf shaft 1A, thereby reducing impact wobble.

[0065] In particular, if Q2 / QW ≥ 90%, impact variation can be reduced regardless of which club set of golf shafts is used.

[0066] In the manufacturing method of the golf shaft 1 in this embodiment, the shaft is manufactured by performing stepping on the raw tube 11 after processing such as thickness variation, similar to Figure 11.

[0067] In stepping, the process is performed on the base end side of the raw tube 11, rather than on the tip end 3 of the golf shaft 1, to form the step portion 9 and the base end portion 5 of the golf shaft 1. In this embodiment, stepping is performed on golf shafts 1 of different club numbers, with the lengths of the tip portion 3 and the base end portion 5 being kept constant, to form step portions 9 of different lengths.

[0068] Specifically, as shown in Figure 12, for the shortest golf shaft 1 (1W), an additional straight section 9a of the step section 9, having a length corresponding to the club number, is added between the step section 9 and the base end 5. The addition of the straight section 9a can be achieved by using a base tube 11 of a different length for each club number.

[0069] The rest is the same as in Example 1. [Examples]

[0070] Figure 13 is a schematic diagram comparing the longest and shortest golf shafts in a golf shaft set according to Embodiment 3 of the present invention. Embodiment 3 shares the same basic configuration as Embodiment 1, and the same reference numerals are used for corresponding components to omit redundant explanations.

[0071] In Figure 13, the longest golf shaft 1(12) is for a 2-iron, and the shortest golf shaft 1(1W) is for a wedge (W-iron). The total length of these golf shafts 1 is set according to the club number by adjusting the length of the tip section 3, the step section 9, and a portion of the base section 5. Specifically, the length of the step section 9, which is the middle section 7, is the same for all golf shafts 1, while the lengths of the tip section 3 and base section 5 differ.

[0072] In this method of manufacturing a golf shaft 1, after manufacturing golf shafts 1 of the same shape, the tip portion 3 and the base portion 5 are cut according to the club number. In this embodiment, the tip portion 3 of the golf shafts 1 of the other club numbers will be shorter than the tip portion 3 of the longest golf shaft 1.

[0073] Therefore, in this embodiment, although the tip portion 3 becomes longer as the overall length increases, the base portion 5 also becomes longer, thus suppressing the lengthening of the tip portion 3 compared to the comparative example (reference) golf shaft 1A. As a result, the decrease in rigidity of the golf shaft 1 due to the increase in overall length can be suppressed, and even with a long golf shaft 1, impact wobble can be reduced. Otherwise, it is the same as in Embodiment 1. [Explanation of Symbols]

[0074] 1 Golf Shaft 1A standard golf shaft 3 Tip 5 Proximal end 7. Middle section 9 Step section

Claims

1. Each of the golf shafts comprises multiple club numbers of different lengths, each having a multi-stage stepped section between the axial tip and base end, where the outer diameter gradually increases toward the base end, and the tip end having a relatively thicker wall. The aforementioned golf shafts of multiple numbers differ in overall length due to differences in the length of at least a portion of the step section. The ratio of the stiffness of the longest golf shaft to the stiffness of the shortest golf shaft is 90% or more. The stiffness is the stiffness over the entire length range common to the shortest golf shaft and the longest golf shaft. The aforementioned common length range is such that, in the golf shafts of the multiple club numbers, the length from the tip to the position above the base end is within a certain range. Golf shaft set.

2. A golf shaft set according to claim 1, The length of the tip portion is constant from the golf shaft with the longest overall length to the golf shaft with the shortest overall length. Golf shaft set.

3. A method for manufacturing multiple golf shafts of different lengths, each having a multi-stage stepped portion between the axial tip and base end, where the outer diameter gradually increases toward the base end, and the wall thickness of the tip portion is relatively thicker, The total length of the golf shaft is set by adjusting the length of at least a portion of the step portion. The ratio of the stiffness of the longest golf shaft to the stiffness of the shortest golf shaft is 90% or more. The stiffness is the stiffness over the entire length range common to the shortest golf shaft and the longest golf shaft. The aforementioned common length range is such that, in the golf shafts of the multiple club numbers, the length from the tip to the position above the base end is within a certain range. A method for manufacturing golf shafts.

4. A method for manufacturing a golf shaft according to claim 3, The total length of the golf shaft is set by keeping the length of the tip constant and adjusting the length of a part of the step portion. A method for manufacturing golf shafts.

5. A method for manufacturing a golf shaft according to claim 3, The total length of the golf shaft is set by adjusting the length of the tip portion and a portion of the step portion. A method for manufacturing golf shafts.

6. A method for manufacturing a golf shaft according to any one of claims 3 to 5, The length of a portion of the step is the length of the straight portion of the step adjacent to the base end. A method for manufacturing golf shafts.

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