US20050037868A1

US20050037868A1 - Practice golf ball

Info

Publication number: US20050037868A1
Application number: US10/916,681
Authority: US
Inventors: Kunihiro Tamura
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-08-15
Filing date: 2004-08-12
Publication date: 2005-02-17
Also published as: JP3562722B2; JP2004223272A

Abstract

The present invention provides a practice golf ball for approach shots and putting practice for helping golfers to improve the precision of their approach shots and putting when they hit regular golf balls, from which the golfers receive the same feeling of hit as from a regular golf ball. The smaller practice ball has a heavy metal core covered with rubber and the outer surface is coated or covered with a coating or covering material or a surface finishing material. Its weight and resilience are established to give the same feelings of heaviness and hit as the regular golf ball. Using these balls in the practice of applying the club face to the balls toward the target using an approach shot club or a putter, golfers acquire a latent image of the practice golf ball. Thus, the regular golf ball appears to be larger than its actual size. In this manner, golfers become capable of precisely applying the club face to the golf ball and improving the precision of their approach shots and putting.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a practice golf ball, and relates in particular to a practice golf ball primarily suitable for practicing approach shots and putting.
Balls made smaller than those used in official games are often used in practicing ball sports. For example, mini balls having a diameter of 11 cm are used instead of 22 cm soccer balls.
However, conventional mini balls have the same weight as regular soccer balls although they are smaller in diameter. Hence, they give the players the impression that they are heavier than a regular soccer ball. Such balls are acceptable in soccer where players directly kick the ball with their feet. However in golf, where players indirectly hit the ball using a club or a putter, there is a different feel to the hands when the ball is hit, in comparison to the feel with a regular golf ball.
Conventionally, the use of pachinko balls (metal balls) having a diameter of 11 mm for putting practice has been proposed. Putting practice in this case is conducted on a natural or artificial turf, or on a home carpet. For example, a pachinko ball placed on a wood floor runs if the floor is tilted even slightly, and one placed on natural or artificial turf or on a home carpet becomes buried because of its weight, and there is no part left to be hit by a putter. The idea of using pachinko balls for the practice or golf continues, but is impractical.
Light-weight golf balls have been proposed in which a weight, such as a small metal ball, for example a lead ball, is embedded. Such a metallic ball comprises one fourth of the entire ball in terms of its outer dimension. The impact of a shot is absorbed by the outer shell, excluding the weight. Hence, the golfer does not feel the weight or impact on his/her hands.
Alternatively, practice golf balls in which an aluminum alloy is embedded for automated selection by a metal detector have been proposed. Such practice golf balls provide the same effect.
Training balls have also been proposed which have an eccentric center of gravity for significantly complicated and unusual bounce. With such training balls, the complicated and unusual bounce confuses the golfer practicing approach shots and putting, adversely affecting his/her practice.
However, the prior art balls described above do not provide sufficient feel of hit essential to practicing golf. Furthermore, they fail to meet the practice ball requirement that the ball travel in the correct direction when it is precisely shot, which is a problem with the Prior Art.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a practice golf ball for approach shots and putting practice to help golfers to improve the precision of their approach shots and putting when they hit regular golf balls, from which the golfers receive the same feel as from a regular golf ball.
As a result of the inventor's intensive research to resolve the problems associated with the prior art, it was found that obtaining the feeling of hit as close as possible to that obtained from a regular golf ball is useful for improving golf skills, with the knowledge that golfers are advised to use smaller balls than regular balls in terms of outer dimension, and to concentrate on the smaller balls with which to acquire precise shooting skill. The present invention is proposed in view of this perspective. A detailed explanation of the present invention is provided in a separate paragraph below.
The practice golf ball of the present invention comprises a metal ball having a diameter of 15 to 28 mm and a rubber cover that surrounds the metal ball and has a thickness of 1 to 5 mm.
The practice golf ball of the present invention has an overall diameter of 20 to 30 mm and a weight of 15 to 40 g, the cover of which can be made of natural or synthetic rubber.
The practice golf ball of the present invention has a smaller diameter than a regular golf ball and a rubber covering, which becomes deformed upon the impact of a club or a putter. This deformation is not enough to absorb the entire impact because of the limited thickness of the cover.
Therefore, most of the impact is applied to the metal ball. The impact applied to the metal ball produces a counteraction on the club or putter, which is transferred to tho golfer's hands as the feeling of a hit. Using a sufficient number of smaller practice balls, the golfer improves his/her concentration and his/her hands remember the appropriate feeling of hit.
The deformation of the cover, combined with the friction of the rubber surface give the practice golf ball adequate spin in practicing approach shots using a club. The resultant counteraction is transferred to the golfer's hands as the feeling of a spin. Furthermore, the outer dimension of the practice golf ball is established so as not to be buried in the turf or a carpet.
Therefore, indoor and outdoor practical training is available.
According to the present invention, the outer surface of the cover of the practice golf ball of the present invention is coated or covered with a coating or cover material, as a finishing material, to improve the surface durability.
According to the practice golf ball of the present invention, the friction coefficient of the outer surface of the covering can be adjusted. In particular, a smaller friction coefficient can be applied for smooth running in putting practice.
The covering of the practice ball of the present invention has multiple dimples, the size of which can be arbitrarily established.
According to the practice golf ball of the present invention, in practice the dimples serve to give the appearance closer to that of a regular ball, and enables adjusting the friction coefficient of the ball surface as necessary.
The practice golf ball of the present invention is characterized by the fact that the metal ball is made of a ferromagnetic substance. In this instance, the ferromagnetic substance includes iron and the use of a magnet.
According to the practice golf ball of the present invention, with the introduction of a magnet into the practice target, the practice golf ball is attracted to the magnet i.e. practice target. This attraction can be used as the assumed dropping into a cup, without the actual use of a cup, useful for cultivating a sense of distance for approach shots.

DETAILED EXPLANATION OF PREFERRED EMBODIMENTS

The present invention is described in detail hereafter, using embodiments. However, the present invention is not confined to these embodiments.
The practice golf ball of the present invention comprises a metal ball having a diameter of 15 to 28 mm and a rubber cover that surrounds the metal ball and has a thickness of 1 to 5 mm. The practice golf ball of the present invention has a total weight of 15 to 40 g and an overall diameter of 20 to 30 mm. The metal ball can be made of any metal having a specific weight, preferably iron or an iron alloy.
The covering can be made of natural or artificial rubber, preferably silicon rubber, fluorine rubber, or urethane rubber.
The thickness of rubber can be appropriately selected in the range of 1 to 5 mm, within which range the same effect can be obtained. The practice golf ball of the present invention can be produced by introducing rubber material into a metal mold, placing an annealed copper iron ball, and pressure molding it in the metal mold, and accomplishing abrasive finishing of the surface. In order to improve the durability of the practice golf ball of the present invention, coating finish can be applied where necessary. Known covering materials such as balata and ionomer resins can be used to cover the outer surface of the rubber. In addition, multiple dimples can be formed on the cover, the size of which can be arbitrarily established. It is preferable that the dimples be sized according to the surface area and that they be similar to those of a regular golf ball in appearance.

Experiment 1

An annealed copper iron ball having a diameter of 15 mm is covered with silicon rubber having a thickness of 5 mm, giving it an overall diameter of 25 mm and a weight of approximately 20 g.

Experiment 2

An annealed copper iron ball having a diameter of 18 mm is covered with silicon rubber having a thickness of 1 mm, giving it an overall diameter of 20 mm and a weight of approximately 24 g.

Experiment 3

An annealed copper iron ball having a diameter of 21 mm is covered with silicon rubber having a thickness of 2 mm, giving it an overall diameter of 25 mm and a weight of approximately 40 g.

Experiment 4

An aluminum alloy (JIS AL2011) ball having a diameter of 21 mm is covered with silicon rubber having a thickness of 1 mm, giving it an overall diameter of 23 mm and a weight of approximately 15 g.

Experiment 5

An aluminum alloy (JIS AL2011) ball having a diameter of 28 mm is covered with silicon rubber having a thickness of 1 mm, giving it an overall diameter of 30 mm and a weight of approximately 34 g.

Experiment 6

The outer surface of Experiment 1 is acryl coated.

Experiment 7

The outer surface of Experiment 2 is acryl coated.

Experiment 8

The outer surface of Experiment 3 is acryl coated.

Experiment 9

The outer surface of Experiment 4 is acryl coated.

Experiment 10

The outer surface of Experiment 5 is acryl coated.

Experiment 11

The outer surface of Experiment 1 is covered with balata covering material.

Experiment 12

The outer surface of Experiment 2 is covered with balata covering material.

Experiment 13

The outer surface of Experiment 3 is covered with balata covering material.

Experiment 14

The outer surface of Experiment 4 is covered with balata covering material.

Experiment 15

The outer surface of Experiment 5 is covered with balata covering material.

TABLE 1


Handicap	Approach	P-wedge	S-wedge	Putt

A
H-6	80% (10/8)	80% (10/8)	80% (10/8)	100% (70%)
H-12	70% (10/7)	70% (10/7)	70% (10/7)	90% (60%)
H-18	70% (10/7)	70% (10/7)	60% (10/6)	90% (60%)
H-24	60% (10/6)	60% (10/6)	50% (10/5)	70% (50%)
H-36	40% (10/4)	40% (10/4)	30% (10/3)	60% (30%)
More than	30% (10/3)	20% (10/2)	20% (10/2)	50% (20%)
H-96
B
H-6	70% (10/7)	70% (10/7)	60% (10/6)	90% (40%)
H-12	50% (10/5)	40% (10/4)	40% (10/4)	70% (30%)
H-18	40% (10/4)	30% (10/3)	30% (10/3)	50% (20%)
H-24	40% (10/4)	30% (10/3)	20% (10/2)	60% (10%)
H-36	30% (10/3)	20% (10/2)	20% (10/2)	80% (0%)
More than	20% (10/2)	10% (10/1)	0% (10/0)	20% (0%)
H-36
C
H-6	100%	100%	90% (10/9)	100% (80%)
H-12	90% (10/9)	90% (10/9)	80% (10/8)	100% (70%)
H-18	80% (10/8)	80% (10/8)	70% (10/7)	100% (70%)
H-24	80% (10/8)	70% (10/7)	60% (10/6)	90% (50%)
H-36	70% (10/7)	60% (10/6)	60% (10/6)	70% (40%)
More than	50% (10/5)	50% (10/5)	40% (10/4)	50% (30%)
H-36
D
H-6	80% (10/8)	80% (10/8)	90% (10/9)	100% (80%)
H-12	80% (10/8)	70% (10/7)	70% (10/7)	90% (50%)
H-18	70% (10/7)	60% (10/6)	60% (10/6)	80% (50%)
H-24	60% (10/6)	60% (10/6)	60% (10/6)	70% (30%)
H-36	40% (10/4)	40% (10/4)	20% (10/2)	60% (20%)
More than	30% (10/3)	30% (10/3)	20% (10/2)	50% (10%)
H-36
E
H-6	90% (10/9)	80% (10/8)	80% (10/8)	100% (70%)
H-12	80% (10/8)	70% (10/7)	70% (10/7)	90% (60%)
H-18	70% (10/7)	60% (10/6)	60% (10/6)	80% (60%)
H-24	60% (10/6)	60% (10/6)	50% (10/5)	70% (50%)
H-36	40% (10/4)	30% (10/3)	30% (10/3)	60% (30%)
More than	30% (10/3)	20% (10/2)	20% (10/2)	60% (20%)
H-36

The left half of Table 1 gives the results of an experiment in which beginning to advanced level golfers hit ten each of regular golf balls (having a diameter of approximately 43 mm and a weight of approximately 46 g) and the practice golf balls of Experiment 1 of the present invention (having a diameter of approximately 25 mm and a weight of approximately 20 g) toward a target approximately 4 m away using an approach shot club and a putter in order to prove the effect of the practice golf balls of Experiment 1.
In this experiment, the golfers first hit the regular golf balls (A), then hit the practice golf balls of Experiment 1 (B), and finally hit the regular golf balls again (C). For comparison, the golfers hit urethane balls (D) having a diameter of 35 mm, which is between A and B in size, and a weight of approximately 2 g (D) and, then, hit the regular balls (E). These results are shown in the right half of Table 1.
In Table 1, for example a number (10/8) suggests 8 nice shots and 2 missed shots out of 10 shots. The numbers outside of parentheses, such as 80%, suggest that the impact rate (nice shot rate) was 80% for that case. For putting, numbers in parentheses suggest the target rate (the target touch rate).
Approach shots were made using any clubs (for example No. 7 iron) except for pitching wedges (P-wedge) and sand wedges (S-wedge).
According to this experiment, improvements were observed in both the impact rate and target touch rate when a practice golf ball of Experiment 1 (B) was used while little improvement was observed when a urethane ball having a diameter of 35 mm was used. An advanced level golfer provided comments on his experience using the practice golf ball of Experiment 1 (B) and said that he felt the impact, which helped him to acquire a feeling of distance through practice.
When he hit a regular golf ball after the practice ball of Experiment 1 of the present invention, the advanced level golfer said that the ball looked significantly larger, which made him believe that he could hit the ball at any point, allowing him to apply the club face to the ball. The intermediate level golfer said that the ball looked larger, which gave him a secure feeling, allowing him to make a clean hit. The beginning level golfer said that the ball looked larger and easier to hit.
Based on the experiments in Table 1, the golf ball of Experiment 1 of the present invention was more effective for the beginner, who improved both his impact rate and target touch rate by 10 to 30%.

All of the golfers, from the beginning to the advanced level, emphasized that they felt easy about hitting the ball. Intermediate and advanced level golfers also showed an improvement of 10 to 20%. Concerning the impact he received from the practice golf ball of the present invention, the advanced level golfer said that he received the same feel of hit from it as from a regular golf ball. Therefore, the practice golf ball of the present invention provides an immediate effect in golf practice.

TABLE 2


H-12	H-24	H-36

	Approach	Putting	Approach	Putting	Approach	Putting

Regular Ball	70% (10/7)	90% (60%)	60% (10/6)	70% (50%)	40% (10/4)	60% (80%)
(before practice)
Experiment 1	50% (10/5)	70% (30%)	40% (10/4)	50% (10%)	30% (10/3)	30% (0%)
Regular Ball	90% (10/9)	100% (70%)	80% (10/8)	90% (50%)	70% (10/7)	70% (40%)
Experiment 2	40% (10/4)	50% (10%)	20% (10/2)	40% (0%)	10% (10/1)	20% (0%)
Regular Ball	100%	100% (80%)	90% (10/9)	90% (70%)	80% (10/8)	80% (50%)
Experiment 3	50% (10/5)	70% (30%)	40% (10/4)	50% (10%)	30% (10/3)	30% (10%)
Regular Ball	90% (10/0)	100% (70%)	80% (10/8)	60% (50%)	70% (10/7)	70% (40%)
Experiment 4	40% (10/4)	50% (30%)	20% (10/2)	40% (0%)	10% (10/1)	20% (0%)
Regular Ball	100%	100% (80%)	90% (10/9)	90% (70%)	80% (10/8)	80% (50%)
Experiment 5	60% (10/6)	60% (20%)	50% (10/5)	50% (20%)	40% (10/4)	40% (20%)
Regular Ball	90% (10/9)	100% (80%)	70% (10/7)	90% (50%)	60% (10/6)	70% (30%)
Experiment 6	50% (10/5)	70% (40%)	40% (10/4)	50% (20%)	30% (10/3)	30% (10%)
Regular Ball	90% (10/9)	100% (70%)	70% (10/7)	90% (50%)	60% (10/6)	70% (40%)
Experiment 7	40% (10/4)	50% (30%)	30% (10/3)	40% (20%)	10% (10/1)	20% (0%)
Regular Ball	100%	100% (80%)	90% (10/9)	90% (70%)	80% (10/8)	80% (50%)
Experiment 8	50% (10/5)	70% (40%)	40% (10/4)	50% (20%)	30% (10/3)	30% (10%)
Regular Ball	90% (10/9)	100% (70%)	70% (10/7)	90% (50%)	60% (10/6)	70% (40%)
Experiment 9	40% (10/4)	50% (20%)	20% (10/2)	40% (20%)	10% (10/1)	20% (0%)
Regular Ball	100%	100% (80%)	90% (10/0)	90% (70%)	80% (10/8)	80% (50%)
Experiment 10	60% (10/6)	70% (50%)	50% (10/5)	60% (30%)	40% (10/4)	40% (20%)
Regular Ball	90% (10/9)	100% (60%)	70% (10/7)	90% (50%)	60% (10/6)	70% (30%)
Experiment 11	50% (10/5)	70% (50%)	40% (10/4)	50% (20%)	80% (10/3)	30% (20%)
Regular Ball	90% (10/9)	100% (70%)	70% (10/7)	90% (50%)	60% (10/6)	70% (40%)
Experiment 12	40% (10/4)	50% (20%)	20% (10/2)	40% (20%)	10% (10/1)	20% (10%)
Regular Ball	100%	100% (80%)	90% (10/9)	90% (70%)	80% (10/8)	80% (60%)
Experiment 13	50% (10/5)	70% (50%)	40% (10/4)	50% (20%)	30% (10/3)	30% (20%)
Regular Ball	90% (10/9)	100% (70%)	70% (10/7)	90% (50%)	60% (10/6)	70% (40%)
Experiment 14	40% (10/4)	50% (20%)	20% (10/2)	40% (20%)	10% (10/1)	20% (10%)
Regular Ball	100%	100% (80%)	90% (10/9)	90% (70%)	80% (10/8)	80% (50%)
Experiment 15	60% (10/6)	70% (60%)	50% (10/5)	60% (40%)	40% (10/4)	40% (20%)
Regular Ball	90% (10/9)	100% (70%)	70% (10/7)	90% (50%)	60% (10/6)	70% (30%)

Table 2 shows the results of an experiment in which golfers having handicaps 12, 24, and 36, respectively, hit 10 each of the practice golf balls of Experiments 1 to 15 and, then, regular golf balls (43 mm in diameter, approximately 46 g in weight) using an approach shot club and a putter toward a target approximately 4 m away in order to prove the effect of the practice golf balls of Experiment 1 to 15.
It is understood from the results that two series of Experiments 2, 7, 12 and Experiments 4, 9, 14 were most effective, followed by Experiments 1, 6, 11 series, Experiments 3, 8, 13 series, and Experiments 5, 10, 15 series.
The practice golf ball of the present invention is smaller than a regular golf ball in diameter. The heavy core is covered with rubber, in which the weight and resilience are established to give golfers the feel of heaviness and hit.
Using smaller practice golf balls enables golfers to improve their concentration. The practice golf ball of the present invention has a rubber covering, which becomes deformed when hit by a golf club or putter. This deformation is not enough to absorb the impact because of the limited thickness of the cover.
Hence, most of the impact is applied to the metal ball. The impact applied to the metal ball produces a counteraction to the club or putter, which is transferred to the golfer's hands as the feeling of a hit. In addition, deformation of the covering combined with the friction of the rubber surface gives the practice golf ball adequate spin in practicing approach shots using a club. The counteraction is transferred to the golfer's hands as the feeling of a spin. Furthermore, the outer dimension of the practice golf ball is established to be sufficiently large so as not to be buried in the turf or a carpet on which it is placed. Therefore, indoor and outdoor practical training is available.
It is well acknowledged that not only physical conditions but also psychological factors such as memory and emotions significantly affect wins/losses or scores in golf. At the approach in golf courses, golfers have the pressure of precisely applying the club face between the golf ball and the ground (turf), suffering from stiff arms because of “ips” indicated psychological rigidity under pressure.
The practice golf ball of the present invention is useful for eliminating this psychological factor. By using the practice golf ball of the present invention, which is smaller than a regular golf ball, golfers subconsciously acquire an impact image through practice under stress. Then, they adjust their motion through the offset of feedback or sensory information. In this manner, golfers become capable of accomplishing approach shots and putting with the regular golf ball with case.

Besides Experiments 1 to 15, the results of experiments are also given using an annealed copper iron ball having a diameter of 13 mm covered with silicon rubber having a thickness of 6 mm, which has an overall diameter of 25 mm and a weight of approximately 12 g (Comparative Experiment 1) and an annealed copper iron ball having a diameter of 12 mm covered with silicon rubber having a thickness of 4 mm, which has an overall diameter of 20 mm and a weight of approximately 9 g (Comparative Experiment 2).

	TABLE 3


	Feeling of Hit
	depending on Handicap

	H-12	H-24	H-36

Experiments 1, 6, 11	∘	∘	∘
Experiments 2, 7, 12	⊚	∘	∘
Experiments 3, 8, 13	⊚	∘	∘
Experiments 4, 9, 14	∘	∘	∘
Experiments 5, 10, 15	∘	∘	∘
Comparative Experiment 1	Δ	Δ	x
Comparative Experiment 2	Δ	x	x

⊚ indicates feeling of hit and follow-up;
∘ indicates feeling of hit;
Δ indicates insufficient feeling of hit;
x indicates no feeling of hit

Consequently, Comparative Experiments 1 and 2 gave an insufficient feeling of hit compared with the practice golf balls of Experiments 1 to 15.
Then, other practice golf balls were tested for feel of hit.

Comparative Experiment A

Commercially available practice balls having a diameter of approximately 43 mm and a weight of approximately 1 g and made of expanded polystyrene. These made a hitting noise on impact, but had no feel of hit.

Comparative Experiment B

Those having a diameter of approximately 35 mm and a weight of approximately 2 g and made of synthetic resin. There was a slight feeling of hit, but no feeling of contact.

Resilient balls having a diameter of approximately 25 mm and a weight of approximately 9 g or a diameter of approximately 20 mm and a weight of approximately 5 g and made of synthetic rubber:
There providing a little feeling of hit, but only a slight feeling of contact. There was No follow-up of the ball to the club head.

Comparative Experiment D

Marbles having a diameter of approximately 17 mm and a weight of approximately 7 g and made of glass:
There was too good a release to give feeling of hit.

Comparative Experiment E

Pachinko balls having a diameter of approximately 11 mm and a weight of approximately 5 g and made of iron:

These has good release and a hard feeling of contact.

TABLE 4


Comparative			Feeling of Hit

Experiment	Diameter (mm)	Weight (g)	H12	H24	H36	Material

Comparative	43 mm	1 g	X	X	X	Expanded Polystyrene
Experiment A
Comparative	35 mm	2 g	X	X	X	Synthetic Resin
Experiment B
Comparative	25 mm	9 g	Δ	X	X	Synthetic Rubber
Experiment C-1
Comparative	20 mm	5 g	X	X	X	Synthetic Rubber
Experiment C-2
Comparative	17 mm	7 g	X	X	X	Glass
Experiment D
Comparative	11 mm	5 g	X	X	X	Iron
Experiment E

⊚ indicates feeling of hit and follow-up;
◯ indicates feeling of hit;
Δ indicates insufficient feeling of hit;
X indicates no feeling of hit

Table 4 gives the results of an experiment in which golfers having handicaps 12, 24, and 36, respectively, hit the balls of Comparative Experiments A to E using an approach shot club and a putter and were asked about the feeling of hit. Very little feeling of hit was obtained from Comparative Experiments A to E. Thus, they are not suitable for slow speed owing practice such as approach shots in which ball control is essential.
It is understood from the above results that the practice golf ball of the present invention preferably has a metal ball, or core, having a diameter of 15 to 28 mm and a rubber covering having a thickness ranging of 1 to 5 mm, with an overall diameter of 20 to 30 mm and a weight of 15 to 40 g.
The practice golf ball of the present invention is smaller than a regular golf ball in diameter.
Using these for practice, golfers can improve the precision of approach shots and putting when they hit a regular golf ball. Furthermore, golfers feel the hit, which results in more effective practice. In particular, the practice golf ball of the present invention has the following characteristics in terms of feeling of hit:

- (1) A relatively heavy metal core serves to give the same feeling of hit as the regular golf ball for smaller balls.
- (2) The light outer part (rubber) and the heavy inner part (metal) create smaller inertia efficiency (the magnitude of inertia of a rotating object, which is determined by the mass distribution about the rotation axis) and an increased spin rate. This serves to give the same feeling of hit as a regular golf ball for smaller balls.
- (3) The ball has soft rubber surface. The follow-up of the ball to the club face is easily controlled for smaller balls.

Claims

1. A practice golf ball comprising a metal ball having a diameter of 15 to 28 mm and a cover that surrounds the metal ball and has a thickness of 1 to 5 mm, thus having an overall diameter of 20 to 30 mm and a weight of approximately 15 to 49 g.

2. The practice golf ball according to claim 1 wherein the cover is made of rubber.

3. The practice golf ball according to claim 1 wherein the outer surface of the cover is covered with a surface finishing material.

4. The practice golf ball according to claim 3 wherein the surface finishing material is a coating or covering material.

5. The practice golf ball according to claim 4 wherein the coating material is acryl coating material.

6. The practice golf ball according to claim 4 wherein the coating material is balata covering material.

7. The practice golf ball according to claim 2 wherein multiple dimples are formed on the cover.

8. The practice golf ball according to claim 1 wherein the metal ball is made of a ferromagnetic substance.

9. The practice golf ball according to claim 8 wherein the metal ball is made of iron.

10. The practice golf ball according to claim 8 wherein said metal ball is made of iron alloy.