Vibration finishing method and apparatus for same

A vibration finishing method and apparatus in which the surface roughness and form of a hole in a compound material such as a printed board can be made excellent and the working accuracy of the hole can be significantly improved and the working cost of the hole can be lowered. In the punch pressing device, a compound material is fixed to a lower metal mold having a lower die hole into which a punching tool can be inserted. While the compound material is held between the lower metal mold and a pressing plate and pressed by pressing members provided with the pressing plate having an upper die hole into which the punching tool can be inserted, a minute-vibration of frequency of several ten hertz is applied onto the punching tool and then, the compound material is punched out. After that, the punching tool is temporarily drawn from the hole to be worked in the compound material. The punching tool is re-inserted into the worked hole in the compound material while a non-vibration or the minute vibration of frequency of several ten hertz is applied again onto the punching tool.

FIELD OF THE INVENTION 
The present invention relates to a punching and hole-working method by 
means of a press for a printed board or the like composed of a compound 
material, and more particularly to a vibration finishing method and 
apparatus for forming holes in a printed board by means of a press. In 
this specification, words "a compound material" means a compound material 
consisting mainly of a thermoplastic resin as a matrix and mixed with a 
reinforced material or a filler such as a glassfiber, a carbonfiber or a 
resin, which thermoplastic resin including an 
ABCresin(acrylnitril-butadiene-styrene), rigid PVC(rigid polyvinyle 
chrorido), polycarbonate, or the like. 
BACKGROUND OF THE INVENTION 
Conventionally, as methods for boring holes such as through-holes in a 
printed board (referred to as "board", hereafter), a drilling method and a 
punching and hole-working method by means of a press, etc. have been 
employed. In the case of a method by which the board is directly subjected 
to cutting and punching work by means of a drill, the surface roughness 
Ra(avarage surface roughness from the centerline of a surface) of the 
inner face of the worked hole is generally Ra 10 .mu.m to 30 .mu.m, the 
hole itself having an excellent configuration. This technique has been 
most frequently utilized for through-hole processing and has considerably 
high reliability. However, through-holes have had to be directly worked 
one by one by means of a drill, and therefore, defects have occurred in 
that the efficiency of working the holes is considerably low and the cost 
thereof is unfavorably high. 
On the other hand, in the case of what is called a single-sided punch press 
process in which a board is attached to a die on which die holes are bored 
and through-holes are formed in the board by means of a punching tool 
(referred to merely as "a punch" hereinafter which is provided in 
alignment with the die holes, through-holes can be processed in a short 
time and at lowered cost, giving this punch press method excellent 
productivity and enabling it to be utilized for various kinds of 
hole-forming processes. In addition, this technique has an advantage in 
that a complicated hole-forming process for a special shaped hole or the 
like can be simply made. However, various types of problems have been 
brought about in that cracks are formed between the holes, or the 
peripheral portions of the holes are whitened, depending on the material 
of the board, which disadvantageously destroys plasticity. Thus, in order 
to solve these problems, the printed board has had to be heated so that 
the cracks can be reduced, which reduces the productivity of the press 
machine. In this case, however, there has been another problem in that the 
dimensional accuracy of the holes deteriorates because of the expansion 
and contraction of the material. 
The dimensional accuracy of the holes under ordinary temperatures in the 
press process by means of a punch will be described with reference to FIG. 
7. As illustrated in FIG. 7, the dimensions of a hole in the upper and 
lower surfaces 51 and 52 of the board 55 are respectively formed to be 
substantially the same as the diameter 53a of a punch 53 and the diameter 
54a of a die 54 respectively. However, the intermediate part of the hole 
swells because of the restorative action of the board 55. The dimensional 
change of the diameter of this swelling part 56 is not generally constant 
due to conditions such as the thickness of the board, etc, but is 
generally speaking as small as 0.05 mm to 0.2 mm in diameter 53a for the 
hole having a diameter of about from 0.8 mm to 1.5 mm Further, the surface 
roughness of the inner surface 57 of the punched hole is extremely bad at 
Ra 140 .mu.m or more, since the length of a broken surface 57b thereof is 
larger than that of a sheared surface 57a of the upper part. Therefore, 
this conventional punch pressing technique has not been able to be 
employed for processing through-holes. 
Additionally, as shown in FIG. 8, in a case in which the speed of a press 
is lowered and the clearance of the diameter of a die 54 is made smaller 
than that of a punch 53, the length of a sheared surface 57c can be made 
longer than that of the above-described sheared surface 57a and the length 
of a broken surface 57d can be made shorter than the broken surface 57b. 
However, the surface roughness is limited to Ra 100 .mu.m to 120 .mu.m, 
which is only slightly improved over the case stated above. Other results 
have not differed from those in the case shown in FIG. 7. 
Thus, there has been proposed a punching method in which a punching process 
is carried out twice so that the roughness of the inner surface of the 
punched hole is improved. According to this punching method, in a first 
process the board is initially punched using a punch of 0.1 mm smaller 
dismeter than that of the finished dimension. Thereafter, the swelling 
parts of the board are designed to be cut by means of a punch of the 
finished dimension. In accordance with this method, as illustrated in FIG. 
9, the broken surface is significantly decreased, and the surface 
roughness becomes Ra 60 .mu.m to 80 .mu.m, improving the accuracy of the 
hole. However, problems have occurred in that it is difficult to obtain 
the positional accuracy of holes between the first process and the second 
process and that the pressing process is divided into two steps. 
Therefore, these are serious problems in terms of mass production. 
Still another conventional punching technique is-disclosed in Japanese 
Unexamined Patent Publication No. Sho. 57(1982)-102310. As can be seen in 
FIG. 10, a board 61 is sandwiched between upper and lower dies 62 and 63, 
and the upper and lower punches 66 and 67 are provided so as to be opposed 
in die holes 64 and 65 formed in the upper and lower dies 64 and 65. The 
board 61 is punched while the upper and lower punches 66 and 67 
reciprocate upward and downward with the board 61 held by the upper and 
lower punches 66 and 67 and the dies 62 and 63. After the board 61 is 
punched, the upper and lower punches 66 and 67 are reciprocally moved 
upward and downward. This method is what is called a vibration finishing 
and punching method. However, in accordance with this vibration finishing 
and punching method, the side surfaces of punches, specifically, parts in 
the vicinity of the inside diameter of holes are melted and deformed and 
liable to be sheared because of the vibration energy generated on the 
board held by the punches, which vibrates the upper and lower punches, so 
that the hole may be entirely sheared. Further, in accordance with this 
vibration finishing and punching method, the side surface abuts against 
the inner surface of the hole, which is softened due to the vibration 
energy, and the side surface of the punch is transferred to the inner 
surface of the hole. Therefore, an extremely satisfactory inner surface of 
the hole can be obtained. Therefore, a hole which is extremely favorable 
for a through-hole can be achieved. However, in accordance with this 
method, problems have occurred in that the structure of the machine is 
very complicated, that is, an upper and lower pairs of punch and dice are 
required, and the structure of the metal mold becomes undesirably 
complicated and the cost is raised. In addition, there has been also 
arisen a problem that it is hard to remove punching residue. 
In order to solve these problems, Japanese Unexamined Patent Publication 
No. Sho. 62(1987)-241700 discloses, as an example, a method in which one 
type of vibration is applied to a punch with a single-sided punch press 
structure, the board is punched in such a way that the punching tool is 
moved reciprocally by a minute distance a plurality of times to that a 
hole is punched, rather than punching the board once at a stroke. 
According to this method, such problems as cracks between holes on the 
board and peeling of the base material or the like rarely occur. It 
becomes difficult to occur the destruction of plasticity in the periphery 
of a hole. Material powder or dust of the board which is produced as a 
result of the finely pulverized board is applied and solidified into the 
inner surface of the hole by means of a punching tool. Then the inner 
surface of the hole is cut and finished by virtue of friction between the 
inner surface of the hole and the tool, so that a hole with a remarkably 
favorable inner surface can be formed. These advantages are very similar 
to effects obtained by the above vibration finishing and punching method. 
In contrast to the above vibration finishing and punching method, 
according to the method using the single-sided punch, even when the punch 
is reciprocally moved by a minute distance upward and downward a plurality 
of times or vibration is applied to the punch, heat energy is not 
substantially produced and only mechanical shearing is continuously 
carried out. The sheared inner surface of the hole is not smoothed. In 
other words, while the surface of the hole is melted under frictional heat 
generated due to frictional force, the surface of the punch is not 
transferred to the inner surface of the hole as in the case of the 
vibration finishing and punching method. Therefore, according to the 
single-sided punch method, surface roughness is further improved, but the 
dimensional accuracy is considerably lowered, and further, powder or dust 
is much generated from the bord during work, compared with the vibration 
finishing and punching method. 
SUMMARY OF THE INVENTION 
With the above stated problems fully considered, an object of the present 
invention is to overcome them and to provide a vibration finishing method 
and apparatus which forms holes having fine surface roughness without 
deformation in a composite material board such as printed circuit bord 
with significantly improved accuracy and reduced working cost. 
The above mentioned object and other objects can be accomplished in 
accordance with the present invention by carrying out an improved 
vibration finishing method in a single sided punch pressing device which 
is capable of mounting a composite material such as a printed circuit 
board on a die having a die hole bored therein and provides a punching 
tool which is capable of penetrating the composite material and of being 
inserted into the die hole. In the method the composite material is fixed 
onto the die and a pressing member is provided for pressing the composite 
material. The punching process comprises the steps of punching out the 
composite material by means of the punching tool while the composite 
material being arbitrarily pressed with the pressing member and applying a 
minute vibration of several ten hertz to the punching tool; further, 
drawing the punching tool from a punched hole in the composite material 
while the composite material being arbitrarily pressed with the pressing 
member; and re-inserting the punching tool into the punched hole in the 
composite material by applying a non-vibration or applying again the 
minute vibration of several ten hertz to the punching tool while pressing 
arbitrarily the compound material with the pressing member. 
According to another aspect of the present invention, in a vibration 
finishing method, drawing and re-inserting operations of the punching tool 
are repeated several times to improve the accuracy of a hole shape. 
Further, the non-vibration or the minute vibration of several ten hertz 
applied to the punching tool even after the punching operation finishes 
the inner surface of a hole by the mutual sliding of the punching tool and 
the inner wall of the hole, so that the surface roughness of the inner 
surface of the hole is improved and powder or dust from the board is 
reduced. 
According to still another aspect of the present invention, in a 
single-sided punch pressing device, which is capable of mounting a 
composite material such as a printed circuit board on a die with a die 
hole bored therein, and provides a punching tool which is capable of 
penetrating the composite material and of inserting into the die hole 
while applying a minute vibration of several ten hertz to the punching 
tool, a vibration finishing apparatus is used in which the composite 
material is fixed onto the die, and a pressing member for pressing the 
composite material is provided. The pressing member includes a pressing 
plate abutting against the composite material and a metal mold attaching 
plate to which an upper metal mold is attached with the punching tool 
attached thereto, and holds a fluid cylinder between the pressing plate 
and the metal mold attaching plate so that the cylinder is capable of 
providing an adjustable pressure for the pressing plate. The pressing 
plate is provided a dice hole to which the punching tool is slidably 
fitted with a small gap provided therebetween. 
Further, it will be understood that, in place of the fluid cylinder, the 
pressing member, an elastic member such as urethane or a spring capable of 
providing adjustable pressure for the pressing plate and an adjusting 
member capable of adjusting the resilient force of the elastic member may 
be provided between the pressing plate and the metal mold attaching plate 
Consequently, the pressing force relative to the board can be readily and 
simply controlled by a simpler structure. 
In accordance with the present invention having the above-stated 
construction, when the holes are worked while the vibration of several ten 
hertz is given to the punch, and the pressing members are made to abut 
against the board so that the board is pressed thereby in a single-sided 
punch pressing device, the board is gradually sheared as the punch is 
being inserted into the board in a first hole-work operation. Thus, a hole 
is bored and the punch is inserted into the hole. At this time, the inner 
part of the hole in the board undergoes such force through the pressing 
members as to abut against the side surface of the punch. As a result, the 
inner surface of the hole is pressed to the punch member. Since the 
vibration of several ten hertz is exerted on the punch, the inner surface 
of the hole in the board more strongly abuts against the punch by virtue 
of the pressing force of the pressing members. Consequently, a finely 
sheared surface is more smoothed. 
Although, when the punch is then drawn from the hole, there exists no 
resistance by the punch in the hole bored in the board, the board is 
pressed by the pressing members, and therefore, the longitudinal sectional 
face of the hole in the board is formed a swelling part. When the punch is 
re-inserted into this hole, while applying the non-vibration or the 
vibration of several ten hertz to the punch, then, this swelling part is 
cut and, at the same time, the inner surface of the hole is smoothed again 
by the punch. 
When the punch is again pulled out of the hole, the longitudinal sectional 
face of the hole in the board pressed by the pressing members is again 
formed a swelling part. However, the amount of the swelling part is 
decreased. Furthermore, the sheared surface of the hole is softened 
because of a frictional heat due to the pressing force of the pressing 
members and the vibration of the punch and the internal stress of the 
swelling part is also reduced. Therefore, when the pressing members are 
detached from the board to thereby release the pressing force 
substantially simultaneously with drawing of the punch from the hole, the 
swelling part substantially disappears owing to the elastic return of the 
board and a greatly smooth hole with a high-degree of form accuracy can be 
obtained. More particularly, since the pressing members are designed to 
press the compound material while the penetrations and drawings of the 
punch into/from the holes are repeated, the board is not moved and 
positional accuracy in repeating the insertion and drawing of the punch is 
also satisfactory. 
By this vibration finishing method in a single sided punch-pressing device 
of the present invention, a smothered hole having substantially no 
swelling part and having fine surface roughness without deformation in a 
composite material board such as printed circuit bord with significantly 
improved accuracy and reduced working cost can be bored. 
The pressing members are designed to press a base material toward the 
center of the hole provided in the board based on the pressing force, and 
to be controlled by such a force as to prevent the sectional face of the 
hole from being formed in a swelling or convex surface when the pressing 
force is released. Additionally, the form accuracy of the hole can be 
improved as the punching tool is repeatedly re-inserted into and drawn 
from the hole several times, so that the form accuracy of the hole can be 
improved. If the inner surface of the hole is finished with the mutual 
sliding between the punching tool and the inner wall of the hole, while a 
minute-vibration of several ten hertz is exerted on the punching tool even 
after the punching tool is pulled out of the hole, and then, the inner 
surface of the hole will be worn due to frictional heat or the like and 
the surface roughness thereof will be improved. 
The pressing plate is provided a dice hole to which the punching tool is 
slidably fitted with a small gap provided therebetween so that they press 
the periphery of the hole in the board and also serve as the guide of the 
punch. If a fluid cylinder is employed for controlling the pressing force 
of the pressing members, a complicated control, for example, a control for 
changing the pressing force of the pressing members during the working of 
a hole can be made. Therefore, the most preferable hole punching and 
working conditions can be simply set. 
The pressing members of the present invention are similar to a discharge 
plate for removing a board from the inner part of a metal mold which has 
been generally used in prior art pressing machines. However, the 
conventional discharge plate has not been employed to restrain the 
movement of the board, nor has it taken into consideration the elastic 
deformation of the board. Therefore, the conventional discharge plate does 
not play a role of the present invention. Further, the above-mentioned 
Japanese Unexamined Patent Publication No. sho. 62-241700 discloses a 
clamp for clamping the board. In this Publication, the structure and 
operation of the clamp are not specifically disclosed, however, it can be 
at least said that the clamp is not provided with a function for coping 
with the elastic deformation of the board. Furthermore, Japanese 
Unexamined Patent Publication No. sho. 57-102310 discloses a vibration 
finishing method provided with upper and lower punches. In this method, a 
board is sandwiched between upper and lower dice, however, they have been 
provided in order to prevent a material from moving relative to the 
movement of the upper and lower punches and not provided to conduct the 
same operation as that of the present invention. 
Further, the present invention can be put into practice only by providing a 
vibrating member for applying a vibration to the punch and by providing a 
pressing members for pressing the compound material in the single-sided 
punch pressing device. Therefore, a metal mold which has been 
conventionally used can be successively used, which preferably contributes 
to the provision of an inexpensive vibration finishing method and 
apparatus for working holes at low cost. 
Furthermore, in accordance with the present invention, since the pressing 
force imposed upon the hoard can be simply controlled by the use of an 
adjusting member or a fluid cylinder capable of adjusting the pressing 
force to the board, the most desirable punching conditions can be readily 
and simply set.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An embodiment of the present invention will now be described with reference 
to the accompanying drawings. FIG.. 1 illustrates a main body of a 
vibration finishing and working apparatus. As illustrated in FIG. 1, an 
punching cylinder 2 which is reciprocable and/or viblatile is attached to 
a frame 1 of the main body. To the lower end of an punching cylinder rod 
3, is connected a metal mold attaching plate 4. A pressing cylinder 5 is 
accommodated in the metal mold attaching plate 4. As can be seen in FIG. 
2, a rod of the pressing cylinder 5 is connected to a pressing members 22 
integrally formed with a pressing plate 22a. To the metal mold attaching 
plate 4, an upper metal mold 6 is attached. A lower metal mold 7 is 
attached to a lower frame 8 of the main body. A pressure oil is supplied 
to the punching cylinder 2 through a hydraulic valve 9 from a hydraulic 
power source either not shown. To the upper frame 1 of the main body, a 
position sensor 10 for detecting the position of the metal mold connecting 
plate 4 is attached. 
FIG. 2 is an explanatory view of parts in the metal molds shorn in FIG. 1. 
Referring to FIG. 2, a board 15 to be worked is inserted between the 
pressing plate 22a integrally formed with the pressing members 22 which 
are capable of pressing the board by means of the pressing cylinder 5 and 
the lower metal mold 7. In the pressing plate 22a and the lower metal mold 
7, die holes 24 and 25 are respectively bored which respectively pass 
through in the longitudinal direction. A punching tool 26 is attached to 
the upper metal mold 6 which is mounted on the metal mold attaching plate 
4. The punching tool 26 can be fitted and slid into the die holes 24 and 
25 in the pressing plate 22a and the lower metal mold with a small gap 
left therebetween. Further, the punching tool 26 can be inserted into the 
board 15 along the die holes 24 and 25 by means of the punching cylinder 2 
together with the metal mold attaching plate 4 to which the upper metal 
mold 6 is attached. 
FIG. 3 is a schematic block diagram of a hydraulic control circuit of the 
vibration finishing apparatus of 1. A control valve 9 is controlled by the 
control signal of a control valve amplifier 11. To the control valve 
amplifier 11 is connected a command signal generator 12 for outputting a 
basic command signal 14 to command sine waves of several hertz to several 
ten hertz and a desired small amount feed to the punching tool 26 via the 
punching cylinder 2. A position signal from the position sensor 10 for 
detecting the amount of movement of the punching cylinder rod 3 is 
inputted to a position sensor amplifier 13. Then, at the same time, the 
position signal is also outputted as a feedback signal to the control 
valve amplifier 11. Thus, the control valve amplifier 11 carries out a 
voltage/current conversion so that an error signal between the command 
signal and the feedback signal becomes 0 and outputs a current as a 
control signal to the control valve 9. Accordingly, the cylinder rod 3 and 
the metal mold attaching plate 4 are so always controlled as to move 
following the command signal from the command signal generator 12. 
Further, the pressing cylinder 5 attached to the lower end of the cylinder 
rod 3 is so controlled by a directional control valve 27 as to press the 
board 15 on the lower die 7, and lift up from it. A pressing pressure is 
controlled by an electromagnetic proportional pressure control valve 28 
based on a control current from an electromagnetic proportional pressure 
control amplifier 29. 
An operation of the vibration finishing apparatus according to the 
invention will be described in the following. While a board 15 to be 
worked is inserted between the pressing plate 22a and the lower metal mold 
7 is pressed by the pressing members 22 by means of the pressing cylinder 
5, the punching tool 26 is applied the basic command signals shown in FIG. 
4 with an amplitude of several ten .mu.m to several mm at a frequency of 
several hertz to several ten hertz and the punching tool 26 is lowered. 
Thus, while the upper metal mold 6 integrally formed with the metal mold 
attaching plate 4 and the punching tool 26 are guided by the die hole 24 
of the pressing plate 22a, they are inserted into the board 15 to thereby 
punch out the board 15. The punching tool is further lowered until the 
punching tool reaches the die hole 25 of the lower metal mold. In this 
way, punching operations of an amplitude of several ten .mu.m to several 
mm at a frequency of several hertz to several ten hertz are repeatedly 
performed by the comanded vibration. Once the punching tool is lowered to 
the lower metal mold, the punching tool 26 is lifted up without applying 
vibration until the punching tool is completely drawn from the board 15 
while a board 15 is pressed. At this time, what is called, a shear drop or 
swelling, specifically stated, a convexed swell formed in a part of the 
inner surface of the hole in the board which is caused by virtue of the 
restoring action of the board 15, is generated. In order to remove the 
shear drop or swelling, the punching tool 26 is re-inserted into the hole 
in the board 15, while the vibration is again applied to the punching 
tool. In such a manner, the shear drop or swelled part of the inner 
surface of the hole of the board 15 is removed. Then, the punching 
cylinder is again lifted up to finish the one cycle punching operation. 
At this time, since the pressing cylinder 5 presses the board 15 through 
the pressing plate 22a during the above punching operation. The bord 15 
generates an internal stress therein owing to the pressing force thereof, 
resulting in a lateral pressure exerted upon the punching tool 26 to be 
penetrated into the board 15. Additionally, after the punching tool is 
pulled out of the hole, the pressing force of these pressing members 
causes the inner surface of the hole in the board to forcibly produce 
swelling part. Since the pressing cylinder 5 has a main body side attached 
to the metal mold attaching plate 4, the cylinder 5 moves together with 
the movement of the punching cylinder 2 and recieves an external fore 
caused by the movement of the cylinder 2. However, since the thickness of 
the board 15 is of small, the stroke of the movement of the punching 
cylinder is also small, the pressure can be controlled to a constant value 
by the pressure control valve 28, enabling to controll the board to press 
at a constant pressure. Further, the pressing cylinder 5 is lifted up or 
lowered together with the metal mold attaching plate 4 by the punching 
cylinder 2, even when the pressing cylinder 5 moves in a small stroke, an 
entire stroke can be increased. Therefore, the board 15 can be readily 
attached to or detached from the dies. 
More specifically, even after the board is punched out, the punching tool 
26 may be moved upward and downward in reciprocation, so that the inner 
surface of the hole can be finely finished. Punching residue is discharged 
from the die hole 25. Although, in the above-stated embodiment shown in 
FIG. 4, vibrating and punching operations are carried out two times, 
however, it is to be understood that they may be more repeated depending 
on the shape of a hole or the material of a board. As illustrated in FIG. 
5, after one cycle vibrating and punching operation punching operations, a 
reciprocating movement of the punching cylinder 2 may be repeated without 
applying a vibration while the board 15 is pressed by the pressing members 
22. This method is more effective for the purpose of reducing the swelling 
parts on the inner surface of the hole, rather than for the purpose of 
finishing the inner surface of the hole. 
Alternately, in place of the pressing cylinder 5, as shown in dotted line 
in FIG. 2, an elastic member 5' such as urethane, springs, etc., and an 
adjusting member capable of adjusting the resilient force of the elastic 
member not shorn are employed as an integral part of the longitudinal 
support member 22' of the pressing member 22, so that the pressing plate 
22a is elastically supported by the metal mold attaching plate 4. In this 
case, a pressing force is changed depending upon the movement of the 
punching cylinder 2. However, if the thickness of the board 15 is small, 
then, the pressing force rill not be greatly changed. Thus, the elastic 
member 5' means which is simpler than the above mentioned pressing 
cylinder 5 may be employed. 
Although, in the above stated embodiment, the description is made in 
connection with one punching tool 26, however, as shorn in dotted line in 
FIG. 2, the number of punching tools 26' may be utilized. Therefore, it 
rill be appreciated that various modifications and changes may be made 
without departing from the purport of the invention. Experimental Examples 
FIG. 6 shows a Table illustrating various experimental results when a hole 
is punched and worked by the above mentioned punch press shown in FIG. 1 
under various kinds of conditions, compareing with a prior art single one 
time punching technique by a single-sided punch press (A, B), a prior art 
twice punching technique by a single-sided punch press (C, D), an 
experimental vibration finishing method (B) which do not use the pressing 
cylinder 5 to presse the board 15 by the pressing plate 22a during the 
punching operation, and the vibration finishing method (F) of this 
invention. In each punching methods, punching experiments were conducted 
in terms of the presence or absence of a pressing plate. In the case of 
the present invention, the pressing plate was added to the vibration 
punching method as illustrated in F. In FIG. 6, an inner surface swelling 
of a hole was measured in the surface of a part represented by a hole 
configuration 31 in FIG. 6, a rise was determined in that of a part 
indicated by 32 and the surface roughness Ra of a hole was measured in 
that of a part represented by 33. 
As can be seen in FIG. 6, in accordance with the prior art pressing method, 
the swell parts or the projecting parts were formed and the surface 
roughness Ra was as bad as not less than 60 .mu.m. On the contrary, in 
accordance with the present invention, as shown in F, there were not 
formed swell part or the projecting part and the inner surface of the hole 
was significantly better than those of other examples, and further, 
surface roughness Ra was as good as 30 .mu.m. Particularly, as can be seen 
in the example E, when the pressing plate of the present invention as not 
provided even in the vibration punching work method, the swell part was 
formed. The obtained experiment results of the example E were both 
inferior to those of the present invention example F from the view points 
of the formation of swell in the inner surface of the hole and the surface 
roughness. Therefore, the object of the present invention could not be 
attained in accordance with the method adopted by the example E which 
assures the excellence of the present invention. 
With reference to the above prior art punching and working methods, a pin 
used as a punching tool was generally buckled in case where through-holes 
are worked in the printed board of the thickness of over about 1.6 mm. 
Therefore, the diameter of the pin was limited to over about 0.8 mm in the 
prior art method. In addition, since the surfaces between the holes were 
liable to be cracked, pitches of the through-holes were also limited to 2 
mm, even when the holes in the board were heated. However, in accordance 
with the present invention, when the holes in the board were not heated 
under the operating conditions shown in FIG. 4, the through-holes at a 
pitch of 1.5 mm with a pin whose diameter is 0.5 mm could be formed and 
worked without a buckling and cracking. Furthermore, in the present 
invention, the through-holes could be worked with the punching force of 
approximately 20 tonf, which was 2/3 times as strong as the conventional 
punching force under an ordinary temperature. Therefore, only punching 
force 2/3 time as strong as that of the conventional press may be 
necessary. Moreover, since a large force is not instantaneously applied to 
the board, the generation of destruction, fatigue and inconvenience can be 
greatly reduced in the vibration finishing apparatus and components 
thereof, which results a further additional effects of the vibration 
finishing method and apparatue of the present invention.