U.S. patent application number 13/905311 was filed with the patent office on 2013-12-05 for golf club steel shaft.
This patent application is currently assigned to DUNLOP SPORTS CO. LTD.. The applicant listed for this patent is DUNLOP SPORTS CO. LTD.. Invention is credited to Kiyofumi MATSUNAGA.
Application Number | 20130324289 13/905311 |
Document ID | / |
Family ID | 49670924 |
Filed Date | 2013-12-05 |
United States Patent
Application |
20130324289 |
Kind Code |
A1 |
MATSUNAGA; Kiyofumi |
December 5, 2013 |
GOLF CLUB STEEL SHAFT
Abstract
A golf club steel shaft in which, when a distance from a front
end of the shaft to a center of gravity point of the shaft is
L.sub.G and when a full length of the shaft is L.sub.S, a
center-of-gravity rate Y (%) obtained as L.sub.G/L.sub.S satisfies
51.0.ltoreq.Y.ltoreq.60.0, a shaft weight X (g) satisfies
80.ltoreq.X.ltoreq.140, and a full length of the shaft L.sub.S
(inch) satisfies 30.ltoreq.L.sub.S.ltoreq.42.
Inventors: |
MATSUNAGA; Kiyofumi; (Kobe,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DUNLOP SPORTS CO. LTD. |
Kobe |
|
JP |
|
|
Assignee: |
DUNLOP SPORTS CO. LTD.
Kobe
JP
|
Family ID: |
49670924 |
Appl. No.: |
13/905311 |
Filed: |
May 30, 2013 |
Current U.S.
Class: |
473/323 ;
473/316 |
Current CPC
Class: |
A63B 60/42 20151001;
A63B 60/00 20151001; A63B 53/12 20130101; A63B 2225/02
20130101 |
Class at
Publication: |
473/323 ;
473/316 |
International
Class: |
A63B 53/12 20060101
A63B053/12 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2012 |
JP |
2012-125139 |
Claims
1. A golf club steel shaft in which, when a distance from a front
end of the shaft to a center of gravity point of the shaft is
L.sub.G and when a full length of the shaft is L.sub.S, a
center-of-gravity rate Y (%) obtained as L.sub.G/L.sub.S satisfies
51.0.ltoreq.Y.ltoreq.60.0, a shaft weight X (g) satisfies
80.ltoreq.X.ltoreq.140, and a full length of the shaft L.sub.S
(inch) satisfies 30.ltoreq.L.sub.S.ltoreq.42.
2. The golf club steel shaft according to claim 1, wherein a
thickness of a portion up to 150 mm from a butt end toward a front
end side of the shaft is not smaller than 0.30 mm but not larger
than 0.40 mm.
3. The golf club steel shaft according to claim 1, wherein an outer
diameter of a portion up to 150 mm from a butt end toward a front
end side of the shaft is not smaller than 14.5 mm but not larger
than 15.3 mm.
4. The golf club steel shaft according to claim 2, wherein an outer
diameter of a portion up to 150 mm from a butt end toward a front
end side of the shaft is not smaller than 14.5 mm but not larger
than 15.3 mm.
5. The golf club steel shaft according to claim 1, wherein the
number of steps included in a portion up to 400 mm from a butt end
toward a front end side of the shaft is not less than 5 but not
more than 8.
6. The golf club steel shaft according to claim 2, wherein the
number of steps included in a portion up to 400 mm from a butt end
toward a front end side of the shaft is not less than 5 but not
more than 8.
7. The golf club steel shaft according to claim 3, wherein the
number of steps included in a portion up to 400 mm from a butt end
toward a front end side of the shaft is not less than 5 but not
more than 8.
8. The golf club steel shaft according to claim 4, wherein the
number of steps included in a portion up to 400 mm from a butt end
toward a front end side of the shaft is not less than 5 but not
more than 8.
Description
TECHNICAL FIELD
[0001] The present invention relates to a steel shaft.
BACKGROUND ART
[0002] For golfers, flight distance of a ball is one of the
important factors when selecting a golf club. Therefore, hitherto,
in order to extend the flight distance of the ball, various
improvements have been made with regard to shapes and materials of
elements forming a golf club.
[0003] However, in recent years, in order to enhance fairness of
competition by suppressing excessive flight distance, there have
been regulations set in the rules regarding rebound performance of
a clubface, club length, and inertia moment of a head; and thereby
it is becoming difficult to improve flight distance.
[0004] In such a situation, in view of the fact that initial
velocity of a ball largely influences flight distance, there has
been a proposal (for example, cf. Patent Literature 1) of extending
the club length close to the upper limit regulated by the rule to
increase head speed of a club.
CITATION LIST
Patent Literature
[0005] [PTL1] Japanese Laid-Open Patent Publication No.
2004-201911
SUMMARY OF THE INVENTION
Technical Problem
[0006] However, with the method of increasing head speed of a club
by extending the club length, controllability of the head
deteriorates as the length of the club becomes longer, and it
becomes difficult to hit a ball at a sweet spot of the head. Thus,
a ball smash factor deteriorates and initial velocity of a ball
cannot be stably increased; and, as a result, flight distance of a
ball cannot be improved.
[0007] In order to solve this, it is necessary to increase the
smash factor by reducing the length of the club and increase
initial velocity of the ball by increasing the head weight.
However, simply increasing the head weight leads to a problem where
ease of swinging the club decreases due to inertia moment of the
club now becoming large.
[0008] Therefore, it is conceivable to move the center of gravity
of the shaft toward the butt side (hand side) in order to prevent
the increase of inertia moment of the club without further
increasing the club weight.
[0009] Although it is ordinarily possible to move the center of
gravity of the shaft toward the butt side by increasing the
thickness of the a butt side portion of the shaft; with this
method, a flexural rigidity value EI (kgfm.sup.2) of the butt side
portion of the shaft also increases, and feel of hitting a ball and
directivity of a hit ball deteriorate.
[0010] The present invention has been made in view of such
circumstances, and an objective of the present invention is to
provide a golf club steel shaft that makes it possible to extend
flight distance of a ball while maintaining feel of hitting a ball
and directivity of a hit ball.
Solution to the Problems
[0011] (1) In a golf club steel shaft of the present invention,
[0012] when a distance from a front end of the shaft to a center of
gravity point of the shaft is L.sub.G and when a full length of the
shaft is L.sub.S, a center-of-gravity rate Y (%) obtained as
L.sub.G/L.sub.S satisfies 51.0.ltoreq.Y.ltoreq.60.0,
[0013] a shaft weight X (g) satisfies 80.ltoreq.X.ltoreq.140,
and
[0014] a full length of the shaft L.sub.S (inch) satisfies
30.ltoreq.L.sub.S.ltoreq.42.
[0015] In the golf club steel shaft of the present invention, since
the center-of-gravity rate Y (%), the shaft weight X (g), and the
full length of the shaft L.sub.S (inch) are each set as values
within the above described ranges, it is possible to increase
weight of a golf club head with steel iron, and extend flight
distance of a ball while maintaining feel of hitting a ball and
directivity of a hit ball.
[0016] (2) In the golf club steel shaft according to (1) described
above, a thickness of a portion up to 150 mm from a butt end toward
a front end side of the shaft is preferably not smaller than 0.30
mm but not larger than 0.40 mm.
[0017] (3) In the golf club steel shaft according to (1) or (2)
described above, an outer diameter of a portion up to 150 mm from a
butt end toward a front end side of the shaft is preferably not
smaller than 14.5 mm but not larger than 15.3 mm.
[0018] (4) In the golf club steel shaft according to (1) to (3)
described above, the number of steps included in a portion up to
400 mm from a butt end toward a front end side of the shaft is
preferably not less than 5 but not more than 8.
Advantageous Effects of the Invention
[0019] With the steel shaft according to the present invention, it
is possible to extend flight distance of a ball while maintaining
feel of hitting a ball and directivity of a hit ball.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is an illustrative diagram of a golf club including
one embodiment of a golf club steel shaft of the present
invention.
[0021] FIG. 2 is for describing a method for measuring T-point
strength.
DESCRIPTION OF EMBODIMENTS
[0022] In the following, detailed embodiments of a steel shaft for
a golf club of the present invention will be described with
reference to the accompanying drawings.
[0023] FIG. 1 is an illustrative diagram showing the entirety of a
golf club 1 including a steel shaft (hereinafter, may be simply
referred to as "shaft") for a golf club, according to one
embodiment of the present invention. The golf club 1 includes an
iron type golf club head 2 having a predetermined loft angle, a
shaft 3, and a grip 4. The head 2 has a hosel 6 including a shaft
hole 5 to which a tip end 3a on the front end side of the shaft 3
is inserted and fixed. A butt end 3b at the back end side of the
shaft 3 is inserted and fixed in a grip hole 7 of the grip 4. The
tip end 3a is positioned inside the head 2, and the butt end 3b is
positioned inside the grip 4. It should be noted that, in FIG. 1, a
reference character of "G" indicates the center of gravity (center
of gravity point) of the shaft 3. The center of gravity G is
located on a shaft axis inside the shaft 3.
[0024] Although the weight of the golf club 1 is not particularly
limited in the present invention, it is preferably set within a
range of not smaller than 360 g. If the weight of the golf club 1
is too small, the strengths of respective elements (parts) forming
the golf club 1 become low, and durability of the golf club 1 may
deteriorate. Therefore, the weight of the golf club 1 is preferably
not smaller than 370 g, and further preferably not smaller than 380
g. On the other hand, if the weight of the golf club 1 is too
large, it becomes difficult to perform a swing, and it becomes
difficult to increase head speed. Therefore, the weight of the golf
club 1 is further preferably not larger than 500 g, and
particularly preferably not larger than 490 g.
[0025] Furthermore, the length of the golf club 1 itself is also
not particularly limited in the present invention, and is
ordinarily from 34.0 to 42.0 inches. If the length of the golf club
1 is too small, although a swing can be performed easily, a turning
radius of the swing becomes small, and it becomes difficult to
obtain a sufficient head speed. As a result, the ball speed cannot
be increased, and the flight distance of the ball cannot be
extended. Therefore, the length of the golf club 1 is preferably
not smaller than 34.5 inches, and further preferably not smaller
than 35.0 inches. On the other hand, if the length of the golf club
1 is too large, the head speed decreases since it becomes difficult
to swing the club. Therefore, the ball speed cannot be increased,
and the flight distance of the ball cannot be extended. Therefore,
the length of the golf club 1 is preferably not larger than 41.5
inches, and further preferably not larger than 41.0 inches.
[0026] It should be noted that, in the present specification, "club
length" is a length measured based on the description in "Appendix
II--Design of Clubs" "1. Clubs" "1c. Length" in the Rules of Golf
determined by R&A (The Royal and Ancient Golf Club of Saint
Andrews).
[0027] [Head Configuration]
[0028] The head 2 in the present embodiment is a solid iron head
and has a large inertia moment. With a club having the head 2 with
a large inertia moment, an advantageous effect of improvement in
flight distance can be stably obtained.
[0029] In the present invention, there is no particular limitation
in the material of the head 2, and, for example, titanium, titanium
alloys, stainless steel, maraging steel, soft iron, and the like
can be used. Furthermore, instead of manufacturing the head 2 using
a single material, the head 2 may be manufactured by combining
multiple materials as appropriate.
[0030] In the present invention, although the weight of the head 2
itself is not particularly limited, it is preferably within a range
from 230 to 310 g. If the head 2 is too light, the kinetic energy
of the head 2 cannot be sufficiently provided to the ball, and it
becomes difficult to increase the ball speed. Therefore, the weight
of the head 2 is further preferably not smaller than 235 g, and
particularly preferably not smaller than 240 g. On the other hand,
if the weight of the head 2 is too large, the golf club 1 becomes
heavy and difficult to swing. Therefore, the weight of the head 2
is further preferably not larger than 305 g, and particularly
preferably not larger than 300 g.
[0031] Furthermore, in the golf club 1 of the present embodiment,
the ratio (head weight/club weight) of the head weight and the club
weight is set to be not lower than 0.55 but not higher than 0.70.
If this ratio is too small, the kinetic energy of the head 2
becomes small and obtaining a sufficient ball speed becomes
difficult. Therefore, the ratio is preferably not lower than 0.56,
and further preferably not lower than 0.57. On the other hand, if
the ratio is too large, the head 2 becomes heavy and it becomes
difficult to swing the club. Therefore, the ratio is preferably not
higher than 0.69, and further preferably not higher than 0.68.
[0032] [Grip Configuration]
[0033] In the present invention, there is no particular limitation
in the material and structure of the grip 4, and those commonly
used can be adopted as appropriate. For example, there can be used
one that is obtained by blending and kneading natural rubber, oil,
carbon black, sulfur, and zinc oxide, and molding and vulcanizing
the materials into a predetermined shape.
[0034] In the present invention, although the weight of the grip 4
itself is not particularly limited, it can be ordinarily set to be
not smaller than 20 g but not larger than 55 g. If the weight of
the grip 4 is too small, the strength of the grip 4 becomes low,
and its durability may deteriorate. Therefore, the weight of the
grip 4 is preferably not smaller than 23 g, and further preferably
not smaller than 26 g. On the other hand, if the weight of the grip
4 is too large, the golf club 1 becomes heavy and difficult to
swing. Therefore, the weight of the grip 4 is preferably not larger
than 53 g, and further preferably not larger than 51 g.
[0035] [Shaft Configuration]
[0036] The shaft 3 in the present embodiment is a steel shaft
having a hollow structure and is manufactured with a method
commonly used in the art. The full length of the shaft 3 is
represented as L.sub.S, and the distance from the tip end (front
end) 3a of the shaft 3 to the center of gravity G of the shaft 3 is
represented as L.sub.G.
[0037] A weight X of the shaft 3 in the present invention is set to
be not smaller than 80 g but not larger than 140 g. If the weight
of the shaft 3 is too small, the possibility becomes high for
strengths such as flexural strength to be insufficient due to
having a small thickness. Therefore, the weight of the shaft 3 is
preferably not smaller than 85 g, and further preferably not
smaller than 90 g. On the other hand, if the weight of the shaft 3
is larger than 140 g, it becomes difficult to perform a swing at an
increased speed due to the whole golf club 1 being heavy.
Therefore, the weight of the shaft 3 is preferably not larger than
135 g, and further preferably not larger than 130 g.
[0038] In addition, the length (full length) L.sub.S of the shaft 3
is set to be not smaller than 30 inches but not larger than 42
inches. If the length of the shaft 3 is too small, a turning radius
of the swing becomes small, and it becomes difficult to obtain a
sufficient head speed. As a result, the ball speed cannot be
increased, and the flight distance of the ball cannot be extended.
Therefore, the length of the shaft 3 is preferably not smaller than
32 inches, and further preferably not smaller than 34 inches. On
the other hand, if the length of the shaft 3 is too large, the
inertia moment at the grip end becomes large, and a powerless
golfer can become easily overwhelmed in terms of power. Therefore,
the head speed cannot be increased, and the flight distance of the
ball cannot be extended. Thus, the length of the shaft 3 is
preferably not larger than 41.5 inches, and further preferably not
larger than 41 inches.
[0039] Furthermore, although the position of the center of gravity
itself of the shaft 3 is not particularly limited in the present
invention, it is ordinarily within a range of, for example, for a
shaft whose length is 39 inches, 595 to 505 mm from the tip end 3a
(front end) of the shaft 3. If the position of the center of
gravity G of the shaft 3 is located closer than 505 mm from the
front end of the shaft 3, there is a high possibility of not being
able to increase head speed since the ease of swinging the club is
not improved due to the position of the center of gravity not being
sufficiently moved in the hand side direction. Therefore, the
position of the center of gravity of the shaft 3 from the front end
of the shaft 3 is preferably not closer than 510 mm, and further
preferably not closer than 515 mm. On the other hand, if the
position of the center of gravity G of the shaft 3 is farther than
595 mm from the front end of the shaft 3, there is a high
possibility of strengths such as flexural strength being
insufficient due to a small thickness on the front end side of the
shaft. Therefore, the position of the center of gravity of the
shaft 3 from the front end of the shaft 3 is preferably not farther
than 585 mm, and further preferably not farther than 575 mm.
[0040] In the present invention, when the distance from the front
end of the shaft 3 to the center of gravity G of the shaft is
L.sub.G and when the full length of the shaft 3 is L.sub.S, a
center-of-gravity rate Y (%) obtained as L.sub.G/L.sub.S satisfies
51.0.ltoreq.Y.ltoreq.60.0.
[0041] If the center-of-gravity rate Y is lower than 51.0(%), since
the center of gravity of the shaft is located close to the front
end side of the shaft, the weight of the head has to be reduced in
order to obtain a swing balance equivalent to that obtained from a
hitherto known club, and the degree of freedom in designing a head
becomes small. Thus, the inertia moment of the head becomes small,
and a technique for lowering the center of gravity cannot be
implemented. Therefore, it becomes difficult to achieve a large
ball flight distance. Hence, the center-of-gravity rate Y is
preferably not lower than 52.0, and further preferably not lower
than 53.0.
[0042] On the other hand, if the center-of-gravity rate Y is higher
than 60.0, since the center of gravity of the shaft is located too
close to the back end side of the shaft, even if the weight of the
head is excessively increased in order to obtain a level of ease of
swinging equivalent to that obtained from a hitherto known club,
i.e., the same level of swing balance; it is still difficult to
perform a swing since the club weight is also increased. In
addition, since the weight is allocated on the back end side rather
than on the front end of the shaft, the strength of the front end
side of the shaft becomes small. Therefore, the center-of-gravity
rate Y is preferably not higher than 58.0, and further preferably
not higher than 56.0.
[0043] Furthermore, in the present embodiment, a thickness t of a
portion up to 150 mm from the butt end 3b of the shaft 3 toward the
front end side of the shaft is set to be not smaller than 0.30 mm
but not larger than 0.40 mm.
[0044] If the thickness t is smaller than 0.3 mm, since the center
of gravity of the shaft is located close to the front end side of
the shaft, the weight of the head has to be reduced in order to
obtain a swing balance equivalent to that obtained from a hitherto
known club, and the degree of freedom in designing a head becomes
small. Thus, the inertia moment of the head becomes small, and a
technique for lowering the center of gravity cannot be implemented.
Therefore, it becomes difficult to achieve a large ball flight
distance. Hence, the thickness t is preferably not smaller than
0.32 mm, and further preferably not smaller than 0.34 mm.
[0045] On the other hand, when the thickness t is larger than 0.4
mm, since the center of gravity of the shaft is located too close
to the back end side of the shaft, even if the weight of the head
is excessively increased in order to obtain a level of ease of
swinging equivalent to that obtained from a hitherto known club,
i.e., the same level of swing balance; it is still difficult to
perform a swing since the club weight is also increased. In
addition, since the weight is allocated on the back end side rather
than on the front end of the shaft, the strength of the front end
side of the shaft becomes small. Therefore, the thickness t is
preferably not larger than 0.38 mm, and further preferably not
larger than 0.36 mm.
[0046] Furthermore, in the present embodiment, an outer diameter d
of a portion up to 150 mm from the butt end 3b of the shaft 3
toward the front end side of the shaft is set to be not smaller
than 14.5 mm but not larger than 15.3 mm.
[0047] If the outer diameter d is smaller than 14.5 mm, a flexural
rigidity value EI of the butt side of the shaft becomes too low and
the shaft becomes soft. In addition, since directional stability of
a hit ball deteriorates, the feel obtained when hitting a ball
deteriorates. Therefore, the outer diameter d is preferably not
smaller than 14.7 mm, and further preferably not smaller than 14.9
mm.
[0048] On the other hand, if the outer diameter d is larger than
15.5 mm, the flexural rigidity value EI of the butt side of the
shaft becomes too high, and the feel obtained when hitting a ball
deteriorates since the shaft bends little and is felt as being
hard. Therefore, the outer diameter d is preferably not larger than
15.4 mm, and further preferably not larger than 15.3 mm.
[0049] Furthermore, in the present embodiment, the number of steps
included in a portion up to 400 mm from the butt end 3b of the
shaft 3 toward the front end side of the shaft is set to be not
less than 5 but not more than 8.
[0050] If the number of the steps is less than 5, the flexural
rigidity value EI of the butt side of the shaft becomes too high,
and the feel obtained when hitting a ball deteriorates since the
shaft bends little and is felt as being hard. Therefore, the number
of the steps is preferably not less than 6.
[0051] On the other hand, if the number of the steps is more than
8, the flexural rigidity value EI of the butt side of the shaft
becomes too low and the shaft becomes soft. In addition, since
directional stability of a hit ball deteriorates, the feel obtained
when hitting a ball deteriorates. Therefore, the number of the
steps is preferably not more than 7.
[0052] In addition, in the present embodiment, when compared to a
portion up to 600 mm from the tip end 3a of the shaft toward the
butt end 3b side, the contained amount of retained austenite in the
material of the shaft is set to be larger in a portion toward the
butt end 3b from this 600-mm part. That is, the contained amount of
retained austenite is different in the tip end side of the shaft
and in the butt end side of the shaft, with the boundary
therebetween being the part 600 mm from the tip end 3a of the shaft
toward the butt end 3b side. More specifically, the contained
amount of retained austenite in the portion on the butt end side of
the 600-mm boundary is set to be larger than the tip end side of
the boundary.
[0053] If the "boundary" is located closer than 600 mm from the tip
end 3a of the shaft with respect to the butt end 3b side, the
flexural rigidity value EI of the butt side of the shaft becomes
too low and the shaft becomes soft. In addition, since directional
stability of a hit ball deteriorates, the feel obtained when
hitting a ball deteriorates. Therefore, the "boundary" is located
preferably not closer than 650 mm, and further preferably not
closer than 700 mm.
[0054] On the other hand, if the "boundary" is located farther than
900 mm from the tip end 3a of the shaft toward the butt end 3b, the
flexural rigidity value EI of the butt side of the shaft becomes
too high, and the feel obtained when hitting a ball deteriorates
since the shaft bends little and is felt as being hard. Therefore,
the "boundary" is located preferably not farther than 850 mm, and
further preferably not farther than 800 mm.
Example
[0055] Next, the steel shaft of the present invention will be
described based on Examples; however, the present invention is not
limited only to those Examples.
[0056] 15 golfers having an average head speed of 42 m/s were each
asked to actually hit ten balls by using a 5-iron (club length: 38
inches, club weight: 400 g) having a shaft with a specification
shown in Table 1, and were asked to answer a question regarding the
feel obtained when hitting a ball. The golfers were asked to take
into consideration ease of swinging, directivity of a hit ball, and
flight distance to perform a 5-scale evaluation. An evaluation
obtained from the most number of golfers was adopted.
[0057] 5 points: Very good
[0058] 4 points: Good
[0059] 3 points: Average
[0060] 2 points: Bad
[0061] 1 point: Very bad
[0062] A shaft front end strength (T-point strength) was measured
in accordance with a testing method defined by SG mark. SG-type
three point flexural strength is a SG-type breaking strength
determined by the Consumer Product Safety Association. FIG. 2 is an
illustrative diagram for the method for measuring the SG-type three
point flexural strength. As shown in FIG. 2, load F was applied
downward from above at a load point t3 while the shaft 3 was
supported from below at two support points t1 and t2. The position
of the load point t3 was a position dividing, into two equal parts,
the interval between the support point t1 and the support point t2.
The load point t3 was matched with the point (T-point) that was to
be measured, and measurement was conducted.
[0063] Results of evaluation of feel of hitting a ball, flexural
strength of a shaft front end portion, and flight distance are
shown in Tables 1 to 3.
TABLE-US-00001 TABLE 1 Comparative Comparative Example 1 Example 2
Example 1 Example 3 Example 2 Shaft weight [g] 95 95 95 95 95 Shaft
full length [inch] 38 38 38 38 38 Center-of-gravity rate [%] 49 52
55 58 61 Thickness [mm] of a portion 0.28 0.32 0.35 0.38 0.41 from
butt end to 150 mm therefrom Outer diameter [mm] of a portion 15 15
15 15 15 from butt end to 150 mm therefrom Number of steps 5 5 5 5
5 Contained amount of retained austenite Uniform Uniform Uniform
Uniform Uniform Feel evaluation 1 2 3 4 5 Flexural strength
(T-point) [kgf] 240 230 220 190 160 of front end part Flight
distance [yard] 162 167 170 168 160
TABLE-US-00002 TABLE 2 Example 4 Example 5 Example 1 Example 6
Example 7 Shaft weight [g] 95 95 95 95 95 Shaft full length [inch]
38 38 38 38 38 Center-of-gravity rate [%] 55 55 55 55 55 Thickness
[mm] of a portion 0.35 0.35 0.35 0.35 0.35 from butt end to 150 mm
therefrom Outer diameter [mm] of a portion 14.4 14.7 15 15.3 15.6
from butt end to 150 mm therefrom Number of steps 5 5 5 5 5
Contained amount of retained austenite Uniform Uniform Uniform
Uniform Uniform Feel evaluation 5 4 3 2 1 Flexural strength
(T-point) [kgf] 220 220 220 220 220 of front end part Flight
distance [yard] 162 165 170 165 162
TABLE-US-00003 TABLE 3 Example 8 Example 1 Example 9 Example 10
Example 11 Shaft weight [g] 95 95 95 95 95 Shaft full length [inch]
38 38 38 38 38 Center-of-gravity rate [%] 55 55 55 55 55 Thickness
[mm] of a portion 0.35 0.35 0.35 0.35 0.35 from butt end to 150 mm
therefrom Outer diameter [mm] of a portion 15 15 15 15 15 from butt
end to 150 mm therefrom Number of steps 4 5 6 5 5 Contained amount
of retained austenite Uniform Uniform Uniform Larger in Larger in
tip end butt end side side Feel evaluation 2 3 4 2 4 Flexural
strength (T-point) [kgf] 220 220 220 210 220 of front end part
Flight distance [yard] 162 170 168 168 168
REFERENCE SIGNS LISTS
[0064] 1 iron type golf club [0065] 2 head [0066] 3 shaft [0067] 3a
tip end [0068] 3b butt end [0069] 4 grip [0070] 5 shaft hole [0071]
6 hosel [0072] 7 grip hole [0073] G center of gravity of a shaft
[0074] L.sub.G distance from a tip end of a shaft to the center of
gravity of the shaft [0075] L.sub.S shaft full length
* * * * *