JPH06269522A - Golf club shaft - Google Patents

Abstract

PURPOSE:To provide a shaft which can secure elasticity (flexibility) in the direction of swing of the shaft and reduce deviation in the direction perpendicular to the direction of swing, and which can be prevented from meandering when very fine metallic wires are disposed on a shaft main body, and avoid rusting when surface polishing is carried out. CONSTITUTION:A hollow shaft main body 6 is formed by lamination of reinforcing layers 5a-5c each comprising reinforcing fibers impregnated with a synthetic resin, and very fine metallic wires 7 are disposed around the outer surface of the shaft main body 6 and roughly parallel to the axis of the shaft main body 6, and are greater in number at one radial side portion 6a of the shaft main body 6 than at the other portion. The outside of the very fine metallic wires 7 is covered with a glass prepreg sheet 8 comprising transparent glass fibers impregnated with a thermosetting resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaft that is required to have strength, rigidity, elasticity, etc. against bending and twisting, such as a golf shaft, a badminton racket, a fishing rod, or a structural pipe material. In detail, the performance as a shaft can be improved by having different functions in the diameter direction of the shaft and the direction orthogonal to this, and the meandering of the metal ultrafine wire when the shaft body is reinforced with the metal ultrafine wire is prevented. The present invention relates to a structure capable of preventing rust and the like of a metal ultrafine wire. The shaft of the present invention is suitable for a golf shaft, and will be described below as an example.

[0002]

2. Description of the Related Art FIG. 11 shows a general golf club. This golf club 21 has a cylindrical shaft 22 with a head 23 fixed to a lower end 22a and an upper end 2a.
It has a structure in which a grip 24 is fixed to 2b. The golf shaft 22 is required to have high strength and rigidity against bending and twisting.

As an example of a golf shaft which meets such a demand, there is a golf shaft proposed in Japanese Patent Laid-Open No. 2-193686. This has a structure in which a plurality of carbon sheets are wound to form a tubular shaft body, and metal fine wires are arranged on the outer surface of the shaft body along the axial direction of the shaft body. According to this shaft, substantially the same vibration characteristics as the steel shaft can be obtained, so that it is possible to secure the flexure (swing) at the time of swing, and to obtain the rigidity and strength against bending and twisting while achieving weight reduction. Moreover, since the metal ultrafine wire provided on the surface of the shaft body can be visually observed, the appearance can be improved.

In order to manufacture the above golf shaft, a plurality of carbon sheets obtained by impregnating carbon fibers with a thermosetting resin are wound around a core material to form an inner layer. On the other hand, an extra-fine metal wire is attached to the surface of another carbon sheet at a predetermined pitch under pressure to form an outer-layer sheet, and the outer-layer sheet is formed on the surface of the inner layer. The shaft body is formed by winding so as to be exposed at the.

Next, a tape is spirally wound around and fixed to the outer peripheral surface of the ultrafine metal wire of the shaft body, and in this state, it is heated at about 130 ° C. for about 2 hours to be cured. After that, the core material is removed and the tape is removed, and the surface of the shaft body is polished to be smooth. As a result, a golf shaft is manufactured.

[0006]

By the way, in the above golf shaft, in order to increase the head speed and improve the flight distance, it is necessary to provide the shaft with a bend in the swing direction (direction of arrow A in FIG. 11). Therefore, for this reason, the shaft is configured to be soft in the swing direction. However, in the conventional shaft described above, when the shaft is softened, a shake tends to occur in the direction B orthogonal to the swing direction A, and as a result, the flight direction of the hit ball becomes unstable.

Further, in the case of manufacturing the conventional golf shaft, when the metal ultrafine wire and the carbon fiber are simultaneously heated and cured, the coefficient of thermal expansion of this metal wire is about four times as large as that of the carbon fiber. Therefore, there is a problem that the ultrafine metal wire extends in the axial direction and meanders. As a result, the strength and rigidity of the shaft may decrease, and the appearance may deteriorate. Here, it is conceivable that the metal ultrafine wire is strongly tightened and fixed with the tape, but it is difficult to prevent meandering because the metal ultrafine wire cannot be sufficiently fixed with the tape.

Further, when the surface of the shaft body is polished, the metal fine wire is exposed, so that the metal fine wire is also polished. For example, if a piano wire or a low carbon dual phase steel wire is used, it will be rusted. There is also a problem that is likely to occur. Since the wire diameter of the above-mentioned steel wire and the like is extremely small, about 100 μm, mechanical properties are significantly deteriorated when rust occurs, which is fatal.

The present invention has been made in view of the above-mentioned conventional situation, and can secure the elasticity (softness) of the shaft in the swing direction while reducing the shake in the direction orthogonal thereto, and further, the shaft body can be made of a metal ultrafine wire. An object of the present invention is to provide a shaft that can prevent meandering when arranging wires and can prevent rust from occurring when surface polishing is performed.

[0010]

According to a first aspect of the present invention, a hollow shaft body is formed by laminating a reinforcing layer obtained by impregnating reinforcing fibers with a synthetic resin, and a metal ultrafine wire is attached to the shaft body. The shafts are arranged so as to extend substantially parallel to the axis, and the number of the metal ultrafine wires in one or both diametrical directions of the shaft body is increased more than in other parts so that the shaft is orthogonal to the diametrical direction of the shaft. The shaft is characterized in that the mechanical properties are anisotropic depending on the direction.

According to a second aspect of the present invention, the metal ultrafine wire is arranged on the outer surface of the shaft body, and the outside of the metal ultrafine wire is made of a glass prepreg obtained by impregnating transparent glass fiber with a thermosetting resin. It is characterized in that it is covered with a sheet, and the invention of claim 3 is characterized in that the metal ultrafine wire is formed by subjecting a composite metallographic steel wire of a ferrite phase and a low temperature transformation phase to 99% or more of strong drawing. It is characterized by being a low-carbon dual-phase steel wire having a wire diameter of 100 μm or less and a tensile strength of 300 Kgf / mm ² or more, which has a fibrous fine metal structure by the strong working.

Further, according to the invention of claim 4, the wall thickness of one side or both sides of the hollow shaft main body in the diametrical direction is made thicker than the other parts, and the diametrical direction of the shaft and the direction orthogonal thereto are set. The shaft is characterized by having anisotropy in mechanical properties.

[0013]

According to the shaft of the invention of claim 1, the number of the reinforcing metal fine wires in one side portion or both sides of the shaft main body in the diametrical direction is increased more than in the other portion. According to this, since the thickness of the one side portion or both side portions is made thicker than the other portions, the mechanical characteristics of the shaft with respect to bending and twisting in the diametrical direction are improved as compared with the mechanical characteristics in the orthogonal direction. Can be made. That is, the shaft has different characteristics that it is hard in the diametrical direction and hard to bend, and has high flexibility and easy to bend in the direction orthogonal thereto. Therefore, when this is adopted in, for example, a golf shaft, by setting the above-mentioned diametrical direction having high hardness in a direction orthogonal to the swing direction, the shaft is easily bent in the swing direction and bent in a direction orthogonal to the swing direction. Can be hardened. As a result, it is possible to improve the head speed at the time of hitting the ball while reducing the swing at the time of swinging, and it is possible to stabilize the control of the direction of the hitting ball.

According to the shaft of the invention of claim 2,
Since the metal ultrafine wire arranged on the outer surface of the shaft body is covered with the glass prepreg sheet, the metal ultrafine wire is embedded between the glass prepreg sheet and the reinforcing layer and is firmly fixed by the entanglement of many fibers. It will be. As a result, when the metal fine wire and the reinforcing layer are heated at the same time, it is possible to suppress the elongation of the metal fine wire due to the difference in the coefficient of thermal expansion between them and to prevent the meandering.

According to the second aspect of the present invention, since the glass prepreg sheet is provided as the outermost layer of the shaft body as described above, the extra fine metal wire is not scraped off even if polishing is performed after heat curing. . Therefore, for example, rust can be prevented from occurring when a piano wire or a low carbon dual phase steel wire is adopted. Further, since this prepreg sheet is made of transparent glass fiber, the metal fine wires can be seen through the sheet, so that the appearance can be improved when the prepreg sheet is used for a shaft for sports or leisure such as golf, fishing rod and the like. In this case, the meandering of the ultrafine metal wire as in the conventional case does not occur, and the appearance can be further improved from this point as well.

According to the third aspect of the present invention, the metal ultrafine wire has a tensile strength of 300 to 600 Kgf / mm ² at a wire diameter of 100 μm or less.
Since the low-carbon dual-phase steel wire is adopted, the mechanical properties such as strength, rigidity, and toughness can be further improved while reducing the diameter of the steel wire, which in turn contributes to weight reduction of the shaft.

Here, the low carbon dual phase steel wire is Fe
It is manufactured by subjecting a -C-Si-Mn-based alloy wire rod to strong working by cold drawing. As a result, the low-temperature transformation forming phase consisting of acicular martensite, bainite, or a mixed structure thereof has a composite metal structure in which ferrite phase is uniformly dispersed, and also has a fine fibrous metal structure. (See JP-A-62-20824). Such low carbon dual phase steel wire, tensile strength in diameter 10 to 100 [mu] m is significantly improved and 300 ~600Kgf / mm ^2, yet bending, shear resistant to torsional deformation, excellent in toughness There is.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 8 are views for explaining a shaft according to a first embodiment of the present invention as claimed in claims 1 to 3,
In the present embodiment, the case of application to a golf shaft will be described as an example.

In the figure, reference numeral 1 denotes a golf club to which the structure of this embodiment is applied, which is a lower end portion 2a of a shaft 2.
The wooden head 3 is fixedly attached to the upper end 2b, and the rubber grip 4 is fixed to the upper end 2b. The shaft 2 is tapered from the upper end 2b toward the lower end 2a.

The shaft 2 has a cylindrical shaft body 6 formed by laminating a plurality of carbon prepreg sheets (reinforcing layers) 5a to 5c, and a large number of fine metal wires 7 provided on the surface of the shaft body 6. It has and. The shaft body 6 includes a large number of carbon fibers and a predetermined amount of thermosetting resin,
For example, it is formed by winding sheet-like prepreg sheets 5a to 5c impregnated with an epoxy resin around a core material. The innermost layer sheet 5a and the outermost sheet 5b are oriented so that the carbon fibers are inclined at about 45 degrees with respect to the shaft axis and the carbon fibers intersect each other. The outermost sheet 5c is oriented so that the carbon fibers extend in one direction along the axis of the shaft.

The metal fine wires 7 are arranged substantially parallel to each other along the axial direction of the shaft body 6 and at a predetermined pitch in the circumferential direction. This fine metal wire 7 is the shaft body 6
Of the metal microwire 7 is embedded in the carbon sheet 5c.

The metal ultrafine wire 7 is
A low carbon dual phase steel wire 7a having a wire diameter of 100 μm or less is coated with a Ni plating film 7b of several μm on the outer surface and a resin film 7c is coated on the surface of the plating film 7b. The Ni plating film 7b has a working strain due to plastic working during wire drawing of the low carbon dual phase steel wire 7a, thereby improving self-lubricating property and corrosion resistance, and at the same time, the resin film 7c. Adhesion and adhesion with

The low carbon dual phase steel wire 7a is manufactured by subjecting the composite structure metal wire rod of the ferrite phase and the low temperature transformation phase to the strong working by cold drawing as described above. This steel wire 7a has a fibrous fine metallographic structure in which the processing cells produced by the above-mentioned strong processing are arranged in a fiber shape in one direction,
Moreover, the size of the processing cell and the fiber spacing are 5 to 100Å,
50-1000Å, wire diameter 20-100 μm and tensile strength 300
It is ~ 600 Kgf / mm ² .

Further, as shown in FIG. 1, a plurality of reinforcing metal fine wires 7'are arranged on one side portion 6a of the shaft body 6 in the diametrical direction. It extends along the longitudinal direction of the main body 6. As shown in FIG. 4, the reinforcing metal fine wires 7 ′ are
It is located near the surface of the upper portion in the direction B orthogonal to the swing direction A.

A glass prepreg sheet 8 is formed on the outer surface of the shaft body 6 so as to cover the metal ultrafine wires 7, 7 '. The glass prepreg sheet 8 is made of transparent glass fibers impregnated with a thermosetting resin such as an epoxy resin. As a result, the metal ultrafine wires 7 and 7'are embedded between the carbon prepreg sheet 5 and the glass prepreg sheet 8 and closely adhered in a state in which a large number of fibers are entangled with each other, thereby firmly fixing them. Has been done.

Next, a method of manufacturing the shaft 2 of this embodiment will be described. I. First, a carbon fiber prepreg sheet, which is a base material, is cut into a predetermined shape to form carbon prepreg sheets 5a to 5c.
To form. A state in which a tension is applied to each metal ultrafine wire 7 such that the longitudinal direction of the carbon prepreg sheet 5c which is the outermost layer of the shaft body 6 and the longitudinal direction of the metal ultrafine wire 7 are substantially parallel to each other. Are arranged at a predetermined pitch, and are pressed with a press or the like.

II. Next, the prepreg sheet 5a of the first layer is wound around the tapered rod material, and the sheet 5b of the second layer is wound around the outer surface of the prepreg sheet 5a. At this time, both carbon fibers are inclined at about 45 degrees to the axis,
And they are laminated so as to cross each other.

III. Next, the shaft body 6 is formed by winding the unidirectional fiber sheet 5c on the surface of the sheet 5b such that the metal fine wires 7 of the sheet 5c are exposed on the surface and are substantially parallel to the shaft axis. In this case, one edge portion of the sheet 5c is overlapped, so that the reinforcing metal fine wire 7'exists on the metal fine wire 7 on the diametrical side 6a of the shaft body 6. , The one side 6a
The number of metal ultrafine wires in a part is larger than in other parts.

IV. Further, a glass prepreg sheet 8 is provided on the surface of the shaft body 6 so as to cover the metal ultrafine wires 7, 7 ', and pressure is applied to the glass prepreg sheet 8 for pressure bonding. As a result, each of the metal fine wires 7 and 7'is formed of the carbon prepreg sheet 5
c and the glass prepreg sheet 8 are surrounded and adhered,
Moreover, many fibers are fixed in a entangled state. Here, the amount of the thermosetting resin added to the glass prepreg sheet 8 is preferably in the range of 25 to 45 wt% from the viewpoint of improving the adhesiveness and the adhesiveness.

V. Next, a tape is spirally wound around and fixed on the outer peripheral surface of the glass prepreg sheet 8, and this is heated in a batch furnace at 135 ° C. for about 1 to 2 hours to be cured.
In this case, since the metal ultrafine wire 7 is pressure-bonded with the glass fiber reinforced sheet 8, the elongation due to the difference in the coefficient of thermal expansion is suppressed and the metal wire 7 is kept in a straight state.

VI. After that, the rod is pulled out and the tape is removed, and then the tape traces formed on the surface of the glass prepreg sheet 8 are polished to smooth the surface and adjust the weight. Finally, a transparent coating material is applied to the surface of this and then dried. As a result, the shaft 2 of this embodiment is manufactured.

According to this embodiment, since the glass prepreg sheet 8 is pressure-bonded to the outer surface of the metal ultrafine wire 7 of the shaft main body 6 to fix the metal ultrafine wire 7, the heat generated when the above-mentioned heat curing treatment is performed is performed. It is possible to prevent the fine wire 7 from meandering due to the difference in expansion coefficient, and to avoid deterioration in strength and rigidity. In addition, when the metal fine wire 7 is exposed on the outermost surface of the shaft 2,
The mechanical characteristics such as bending, twisting, and impact do not change when embedded in the glass prepreg sheet 8.

Further, in this embodiment, the shaft body 6 is
Since the glass prepreg sheet 8 is arranged on the surface of the, the metal ultrafine wire 7 is not shaved even if the polishing process after heat curing is performed, the occurrence of rust etc. can be reliably prevented, and the deterioration of mechanical properties is prevented. It can be avoided. Further, the metal fine wires 7 can be seen from the outside through the glass prepreg sheet 8, and the metal fine wires 7 are arranged in a straight line, so that the appearance can be improved.

Further, in the present embodiment, since the low carbon dual phase steel wire 7a is adopted as the metal fine wire 7, the wire diameter is 20 to 100.
It has an extremely high tensile strength of 300 to 600 Kgf / mm ² at μm, and can further improve the mechanical properties against bending and twisting while reducing the weight of the shaft 2. Further, by adopting the low carbon dual phase steel wire 7a, the shaft 2
It is not necessary to reinforce the connecting portion between the lower end portion 2a and the head 3, and it is not necessary to separately provide a reinforcing sheet as in the conventional case.

FIG. 5 is a diagram comparing the weight of the shaft of this embodiment with the weight of a commercially available shaft. In the figure, steel shafts and titanium shafts are 100-
110g, 80-90g for boron shaft, titanium carbon shaft, and Kevlar shaft. In addition, the carbon shaft can be comparatively light weight of 60-80g. On the other hand, the shaft of this embodiment has a lighter weight of 65 to 70 g. By the way, the strength of 20% and the toughness of 45% can be increased by the low carbon dual phase steel wire of 1 Vol%. Therefore, by using the golf club 1 of this embodiment, it is possible to further increase the head speed and obtain the same degree of deflection as a steel shaft, which improves flight distance and controllability at the time of hitting. it can.

In this embodiment, since the reinforcing metal fine wire 7'is provided on the diametrical side portion 6a of the shaft body 6, the golf club 1 is soft in the swing direction A of the golf club 1 and Different performances of being hard in the orthogonal direction B are obtained. Therefore, the swing in the orthogonal direction B at the time of swing can be reduced, and the control at the time of hitting the ball can be stabilized. Moreover, the reinforcing metal fine wires 7'can be arranged by simply overlapping one edge of the prepreg sheet 5c, which can be easily realized. Here, the reinforcing metal fine wire 7'is not necessarily provided over the entire length of the shaft 2 and may be provided at least at the lower end portion 2a of the shaft 2.

6 to 8 are photomicrographs showing the laminated structure of the shaft of this embodiment. In particular, as is clear from FIG. 8, it is understood that the carbon fiber (having a smaller diameter located below the metal ultrafine wire) adheres to the metal ultrafine wire (white circular cross section). Further, in FIG. 6, it can be seen that the metal fine wires are present more in one portion (upper portion) in the diametrical direction of the shaft main body than in other portions.

In the above embodiment, a low carbon dual phase steel wire is used as the metal ultrafine wire, and the steel wire is arranged in a row in the circumferential direction of the shaft body. However, the present invention is not limited to this. The present invention is not limited to this, and a piano wire, a stainless wire, a titanium wire, an amorphous wire or a boron core boron wire may be used, or a plurality of them may be arranged. Also in this case, more metal fine wires are arranged at one side or both sides in the diameter direction than at other portions.

FIG. 9 and FIG. 10 are views for explaining a shaft according to a second embodiment of the invention of claim 4, and in the second embodiment, the case of application to a golf shaft will be described as an example.

In the figure, reference numeral 11 denotes a golf club to which the structure of this embodiment is applied, in which a wooden head 13 is fixed to a lower end 12a of a cylindrical steel shaft 12 and an upper end 12b is made of rubber. It is configured by fixing the grip 14. Further, the shaft 12 is formed in a taper shape whose diameter gradually decreases from the upper end 12b side toward the lower end 12a side.

Thick parts 15a, 15a are formed on both sides of the steel shaft 12 in the diametrical direction, that is, in the direction B orthogonal to the swinging direction A of the golf club 11. The thick portion 15a is formed by bulging the inner surface of the shaft 12 toward the center side and is formed so as to extend the entire length in the axial direction. The portion of the shaft 12 other than the thick portion 15a is a thin portion 15b, and the ratio of the thickness T of the thick portion 15a to the thickness t of the thin portion 15b is approximately 2: 1. . Further, the circumferential length and the thickness T of the thick portion 15a are appropriately set according to the type of club, the target coser, and the like. The thick portion 15a is formed at the same time when the shaft 12 is manufactured by drawing.

Next, the function and effect of this embodiment will be described. According to the shaft 12 of this embodiment, the shaft 12
Since the thick portions 15a are formed on both sides in the direction B orthogonal to the swing direction A of the golf club 11 and the thickness T of the thick portion 15a is made larger than the thickness t of the other portion 15b, Different characteristics are obtained: soft in the sunig direction A and hard in the direction B orthogonal thereto. This makes it possible to reduce the shake when swinging,
In addition, the head speed can be improved, and the flight distance can be improved while the control of the ball striking direction can be stabilized.

Further, in this embodiment, since the two different characteristics described above can be obtained only by changing the wall thickness of the shaft 12, the manufacturing is easy and the cost is hardly increased.

Although the thick portions 15a are thickened on both sides of the shaft 12 in the above embodiment, the shaft of the present invention may be thickened on only one side. Further, the thick portion 15a is formed over the entire length of the shaft 12,
The thick portion of the present invention may be formed only in a part in the longitudinal direction. For example, only the lower end portion 12a of the shaft 12 may be thickened, and in this case, substantially the same effect as the above embodiment can be obtained.

In the second embodiment, the steel shaft has been described as an example. However, for example, a titanium shaft,
It can also be applied to golf clubs made of carbon fiber shafts. Furthermore, in the above-mentioned embodiment, the case where it is applied to a golf shaft has been described as an example, but the shaft of the present invention can also be applied to sports equipment such as a racket for badminton, or leisure equipment such as a fishing rod, and further specified. It can also be applied to structural piping materials to which a large load is applied in the direction, and the applicable range is not particularly limited.

[0046]

As described above, according to the shaft of the invention of claim 1, the number of the reinforcing fine metal wires in one side portion or both side portions in the diametrical direction of the shaft main body is increased more than other portions, and According to the invention of claim 4, since the thickness of the one side portion or both side portions is made thicker than the other portion, different characteristics of being hard in the diametrical direction and soft in the direction orthogonal thereto can be obtained. When the golf ball is used as a golf shaft, for example, there is an effect that the head speed at the time of hitting the ball can be improved while the swinging at the time of swinging is reduced, and the control of the hitting direction can be stabilized.

According to the shaft of the invention of claim 2,
Since the outer surface of the metal ultrafine wire of the shaft body is covered with the glass prepreg sheet, when the metal ultrafine wire and the reinforcing layer are simultaneously heated, it is possible to suppress the elongation of the metal ultrafine wire due to the difference in thermal expansion coefficient between the both. It has the effect of preventing meandering.
In addition, even if the polishing process after heat curing is performed, the metal ultrafine wire is not scraped, so that it is possible to prevent the occurrence of rust when, for example, a piano wire or a low-carbon dual-phase steel wire is adopted. Since the metal fine lines can be seen through the sheet, it has the effect of improving the appearance.

Further, in the invention of claim 3, the metal ultrafine wire has a tensile strength of 300 to 600 Kgf / mm ² at a wire diameter of 100 μm or less.
Since a low-carbon dual-phase steel wire is adopted, the mechanical properties such as strength, rigidity, and toughness can be further improved while reducing the diameter of the steel wire, which in turn contributes to weight reduction of the shaft.

[Brief description of drawings]

FIG. 1 is a sectional view illustrating a golf shaft according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a metal ultrafine wire according to the first embodiment.

FIG. 3 is a perspective view of the golf shaft of the first embodiment.

FIG. 4 is a perspective view of the golf shaft of the first embodiment.

FIG. 5 is a diagram showing an effect of the first embodiment.

FIG. 6 is a micrograph showing the fiber shape of the shaft of the first embodiment.

FIG. 7 is a micrograph showing the fiber shape of the shaft of the above-mentioned Example.

FIG. 8 is a micrograph showing the fiber shape of the shaft of the first embodiment.

FIG. 9 is a sectional view illustrating a golf shaft according to a second embodiment of the present invention.

FIG. 10 is a perspective view of the golf shaft of the second embodiment.

FIG. 11 is a perspective view showing a general golf club.

[Explanation of symbols]

 2 Shafts 5a to 5c Carbon prepreg (reinforcing layer) 6 Shaft body 6a One side part 7,7 'Metal ultrafine wire 7a Low carbon dual phase steel wire 8 Glass prepreg sheet 12 Shaft body 15a Thick part

Claims (4)

[Claims] 1. A hollow shaft body is formed by laminating a reinforcing layer in which a reinforcing fiber is impregnated with a synthetic resin, and a metal ultrafine wire is arranged so as to extend substantially parallel to the axis of the shaft body. , The number of the metal ultrafine wires in one or both diametrical directions of the shaft body is increased more than in other parts, and the mechanical properties are anisotropic in the diametrical direction of the shaft and the direction orthogonal thereto. Shaft characterized by having it. 2. The glass prepreg sheet according to claim 1, wherein the metal ultrafine wire is arranged on the outer surface of the shaft body, and the outside of the metal ultrafine wire is formed by impregnating transparent glass fiber with a thermosetting resin. Shaft characterized by being covered. 3. The ultrafine metal wire according to claim 1 or 2, which is formed by subjecting a composite metallographic steel wire of a ferrite phase and a low temperature transformation phase to a strong drawing of 99% or more, and producing a fibrous shape by the strong working. Fine metal structure with wire diameter 100 μm or less, tensile strength 30
A shaft characterized by being a low carbon dual-phase steel wire of 0 Kgf / mm ² or more. 4. The hollow shaft main body is made thicker at one side portion or at both side portions in the diametrical direction than other portions, so that the mechanical characteristics of the shaft are anisotropic in the diametrical direction and the direction orthogonal thereto. A shaft that is characterized by having characteristics.