Method of and apparatus for dressing cutting edge of cut-off wheel

A dressing apparatus includes: a first body extending parallel to the axis of the cut-off wheel, the first body having a slider member slidable along the longitudinal axis of the first body, the slider member being urged by an urging member so as to be normally retained in an initial position thereof; a second body, slidably connected to the slider member, for movement in a direction perpendicular to both the cut-off wheel's axis and the first body's axis; a drive motor for rotating a pair of grinding wheels connected to the head member, the axes of the grinding wheels being perpendicular to a plane parallel to both the cut-off wheel's axis and the first body's axis, a line which is perpendicular to both of the axes of the grinding wheels being parallel to the first body's axis; and a drive mechanism, interposed between the first and second bodies, for moving the second body so that either of the grinding wheels is brought into contact with the peripheral cutting edge formed on the cut-off wheel to apply a dressing to the peripheral cutting edge. The drive mechanism includes: a cylinder actuator for moving the slider member from its initial position in either of the opposite directions; and a mechanism for causing the second body to move in a direction relative to the slider member simultaneously with the movement of the slider member from its initial position.

BACKGROUND OF THE INVENTION 
This invention relates to a method of and an apparatus for dressing the 
cutting edge of a cut-off wheel which is used, for example, for cutting an 
ingot of semiconductor material into semiconductor wafers. 
In the cutting of a block of semiconductor material such as a silicon ingot 
into slices to produce semiconductor wafers, a cut-off wheel having an 
inner peripheral cutting edge is generally utilized. As shown in FIG. 1, 
this cut-off wheel W is of a disc-like configuration and has an aperture 1 
formed at the center thereof. An inner peripheral cutting edge 2 which 
comprises an electrically deposited diamond-grain coating and the like, is 
formed along the entire inner peripheral portion of the wheel W. The 
cut-off wheel W is secured to a rotary cutting machine by means of 
attaching holes 3 circumferentially disposed in the outer peripheral 
portion of the wheel W and is rotated at a high speed by the cutting 
machine to cause the inner peripheral cutting edge 2 to cut, into slices, 
a silicon ingot 4 which is inserted into the aperture 1 and moved in a 
direction parallel to the cut-off wheel W, as indicated by arrow A. 
The sharpness of such cut-off wheel decreases as the cutting operation is 
repeated since the cutting edge 2 is worn down and the pores on the 
surface of the cutting edge 2 become clogged with a powdery substance. 
This decrease in sharpness causes a variation in thickness and a warp or 
curvature of the cut slices of the ingot, which results in a deterioration 
in quality of the semiconductor wafers. For this reason, it is necessary 
for the cut-off wheel to be occasionally applied with a dressing treatment 
to remove the powdery substance from the pores and to resharpen the 
cutting edge. 
Conventional dressing treatment is applied to the cut-off wheel, for 
example, according to the manner of manual dressing. In the manual 
dressing, an abrasive stick 5, as shown in FIG. 2, is brought into slight 
contact with a dulled portion of the cutting edge 2 of a rotating cut-off 
wheel W and is slid in a direction indicated by arrow B to dress the 
cutting edge 2 gradually. However, a great skill is required for 
continuously effective dressing, since it is difficult for the abrasive 
stick to maintain a proper state of contact with the cutting edge 2 and 
since inadequate pressing of the abrasive stick against the cutting edge 
causes, on the cutting edge 2, such damage that the diamond grains fall 
off. 
U.S. Pat. No. 4,699,118 discloses a dressing apparatus for automatically 
applying a dressing to the cutting edges of cut-off wheels. As shown in 
FIG. 3, this apparatus utilizes two abrasive tapes 6 and 7 travelling 
across a cut-out 8 which is formed in the head portion 9 of the apparatus. 
In the cut-out 8, the abrasive tapes 6 and 7 extend in directions crossing 
each other so that tapes 6 and 7 are able to contact respectively the 
opposite side surfaces 10 and 11 of the cutting edge 2 of a cut-off wheel 
W. However, the head portion 9 is movable merely in a direction parallel 
to the cut-off wheel W, and thus it is not easy for the head portion to 
bring the alternative of the two tapes 6 and 7 into contact with the 
cutting edge 2. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a dressing 
apparatus which is capable of applying a dressing to either of the 
opposite surfaces of the cut-off wheel's cutting edge without causing one 
of the opposite surfaces of the cutting edge to contact grinding means 
such as a grinding wheel. 
Another object of the present invention is to provide a dressing apparatus 
which helps the cutting edge of the cut-off wheel in effectively 
preventing damage during the dressing treatment. 
A further object of the present invention is to provide a method of and a 
apparatus for applying a dressing to the cutting edge of a cut-off wheel, 
which makes it possible to adjust the level of a dressing to be applied to 
the cutting edge of a cut-off wheel. 
With these and other objects in view, one aspect of the present invention 
is directed to a dressing apparatus which includes: fixing means 
detachably mounted on a cutting machine on which a cut-off wheel is 
mounted so as to be rotated about the axis thereof; a first body connected 
to the fixing means and extending generally parallel to the axis of the 
cut-off wheel, the first body having a slider member slidable along the 
longitudinal axis of the first body; a second body slidably connected to 
the slider member of the first body for movement in a direction generally 
perpendicular to both the axis of the cut-off wheel and the longitudinal 
axis of the first body; a head member connected to the second body and 
disposed generally perpendicularly to a plane in which the cut-off wheel 
lies; first drive means, mounted on the head member, for rotating a pair 
of grinding wheels which are connected to the head member for rotation 
about respective parallel axes generally perpendicular to a plane parallel 
to both the axis of the cut-off wheel and the longitudinal axis of the 
first body, the axes of the grinding wheels being disposed so that a line 
perpendicular to both of the axes of the grinding wheels is parallel to 
the longitudinal axis of the first body; means for urging the slider 
member toward an initial position thereof and for thereby normally 
retaining the slider member in its initial position; and second drive 
means, interposed between the first and second body, for moving the second 
body with respect to the first body. The second drive means includes: a 
cylinder actuator for moving the slider member from its initial position 
in either of the opposite directions; and means for causing the second 
body to move in a direction relative to the slider member simultaneously 
with the movement of the first slider member from its initial position in 
either of the opposite direction. After setting the grinding wheels at 
positions opposite hand sides of the cutting edge of the cut-off wheel, 
the cylinder actuator is operated, which causes either of the grinding 
wheels to contact one of the opposite surfaces of the peripheral cutting 
edge of the cut-off wheel to apply a dressing to the peripheral cutting 
edge. 
It is preferred that the head member is pivotally connected to the second 
body for movement about an axis parallel to the axes of the grinding 
wheels. The second body may have stopper means for restricting the pivotal 
movement of the head member toward the cutting edge of the cut-off wheel 
to its initial position in which a line perpendicular to both of the axes 
of the grinding wheels is generally parallel to the longitudinal axis of 
the first body. The second body may also have biasing means for urging the 
head member toward the cutting edge of the cut-off wheel and into its 
initial position. Each of the grinding wheels may be composed of numerous 
abrasive grains bound together by a resilient bond material. During the 
dressing treatment and upon the contact of the grinding wheel with the 
cutting edge of the cut-off wheel, the biasing means and the elastic 
grinding wheels dampen the impact force exerted on both the grinding wheel 
and the cutting edge of the cut-off wheel. Therefore, the cutting edge of 
the cut-off wheel as well as the grinding wheel is helped in preventing 
damage. 
Another aspect of the present invention is directed to a dressing method 
using a grinding wheel. At least one of both the grinding wheel and a 
cut-off wheel is rotated about the axis thereof. Then, the grinding wheel 
is brought into contact with the peripheral cutting edge of the cut-off 
wheel in such a manner that the axis of the grinding wheel is inclined, at 
an angle larger than 0.degree. and smaller than 90.degree., to the axis of 
the cut-off wheel when the axes of the grinding and cut-off wheels are 
viewed from a plane of projection perpendicular to the direction in which 
the grinding wheel and the cut-off wheel are aligned. As the angle between 
the axes of the grinding and cut-off wheels becomes larger, a greater 
scraping is caused between the grinding wheel and the cutting edge of the 
cut-off wheel, and thus a greater dressing is applied to the cutting edge 
2. 
A further aspect of the present invention is directed to a dressing 
apparatus for practicing the dressing method described above. This 
dressing apparatus includes: fixing means detachably mounted on the 
cutting machine on which a cut-off wheel is mounted; a first body 
connected to the fixing means and extending generally parallel to the axis 
of the cut-off wheel; a second body slidably connected to the first body 
for movement along a plane parallel to both the axis of the cut-off wheel 
and the longitudinal axis of the first body; a head member pivotally 
connected to the distal end of the second body for movement about an axis 
generally perpendicular to both the axis of the cut-off wheel and the 
longitudinal axis of the first body, the head member having a side face 
generally parallel to the pivotal axis thereof, the side face intersecting 
a plane in which the cut-off wheel lies; first drive means, mounted on the 
head member, for rotating a grinding wheel which is disposed on the head 
member so as to overlap the side face of the head member, the grinding 
wheel being connected to the side face of the head member for rotation 
about an axis generally perpendicular to the side face; and second drive 
means, interposed between the first and second body, for moving the second 
body with respect to the first body so that the grinding wheel is brought 
into contact with the peripheral cutting edge of the cut-off wheel to 
apply a dressing to the peripheral cutting edge of the cut-off wheel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIGS. 4 to 16, wherein like reference characters designate 
corresponding parts throughout several views, and descriptions of the 
corresponding parts are omitted once given. 
FIGS. 4 and 5 show an embodiment of a dressing apparatus according to the 
present invention. In FIG. 4, reference numeral 15 designates fixing means 
in the form of a magnet stand adapted to be detachably fixed to the body 
of a cutting machine, described later on, to which a cut-off wheel is 
attached. This magnet stand 15 has a first support rod 14 extending upward 
therefrom as viewed in FIG. 4. A second support rod 16 is slidably 
connected at its one end portion to the first support rod 14 for movement 
along the first support rod 14, and extends substantially horizontally 
from the first support rod 14. Suitable means such as a thumbscrew and a 
pair of a wing nut and a screw (not shown) is provided on the connection 
between the first and second support rods 14 and 16 to restrain the 
movement of the second support rod 16. A slat-like first body 17a is 
slidably connected to the second support rod 16 for movement along the 
second support rod 16, and extends horizontally from the second support 
rod 16 so as to be parallel to both the first and second support rods 14 
and 16. Suitable means such as a thumbscrew (not shown) is also provided 
on the connection between the first body 17a and the second support rod 16 
to restrain the movement of the first body 17a. The first body 17a has a 
threaded through hole (not shown), formed therein, which extends between 
upper and lower faces thereof as viewed in FIG. 4. A position-adjusting 
member in the form of a bolt 18 is screwed in the through hole so as to 
pass through the first body 17a. A first linear slider in the form of an 
elongated member 17b (see FIG. 5) is slidably connected to the first body 
17a for longitudinal and horizontal movement along the side face of the 
first body 17a. An air cylinder 20 is interposed between the first body 
17a and the first linear slider 17b to horizontally move the first linear 
slider 17b with respect to the first body 17a. More specifically, the 
cylinder body 20b of the air cylinder 20 is secured to the right end, as 
viewed in FIG. 5, of the first linear slider 17b via a bracket 19a, while 
the plunger 20a of the air cylinder 20 is secured to the first body 17a 
via a bracket 19 b. 
Referring to FIG. 5, a second linear slider 21 is slidably connected to the 
left end of the first linear slider 17b for vertical movement. A 
plate-like second body 22 is fixed at its left end portion to the second 
linear slider 21 so that one of its opposite side faces, namely, an inner 
face 40 confronts the side face 42 of the first body 17a, to which the 
first linear slider 17b is connected. Between this second body 22 and the 
first linear slider 17b, there is interposed first urging means in the 
form of a coil spring 25 for urging the second body upward, as viewed in 
FIG. 4. To the inner face 40 of the second body 22, a V block-shaped 
member is attached at one of its opposite sides in such a manner that the 
V-shaped recess of the V block member 23 opens upward as viewed in FIG. 4. 
A guide roller 24, which is rotatably supported by a shaft 41 projecting 
from the side face 42 of the first body 17a, is received in the V-shaped 
recess of the V block member 23. This guide roller 24 is pressed, by means 
of the coil spring 25, against the slanting upper face 23a of the V block 
member 23 so as to roll along the slanting face 23a. That is, when the 
solenoid valve of the air cylinder 20 is open, the guide roller 24 is kept 
in the bottom of the V-shaped recess of the V block member 23, resulting 
in the second body 22 being in its initial position shown in FIGS. 4 and 
5. An adjustable stopper means in the form of a vertical screw 26 is 
threadedly engaged with the second body 22. This screw 26 cooperates with 
a projection (not shown) disposed on the first body 17a to restrict the 
downward movement of the second body 22 to a predetermined level. That is 
to say, when the second body 22 is moved downward to the predetermined 
level, the lower end of the screw 26 butts against the projection on the 
first body 17a. 
Referring further to FIGS. 4 and 5, a head member 27a is secured to the 
left end of the second body 22. This head member 27a is of a box-like 
configuration without the upper and lower end walls, and has a cut-out 44 
formed in the lower portion thereof so as to open downward. A driving 
motor 27b is mounted on one of the side faces of the headmember 27a which 
is substantially parallel to the second body 22. A driving pulley 27c 
firmly fits around that portion of the motor's rotation shaft projecting 
into the inside of the head member 27a. A pair of rotary shafts 46 and 46, 
each passing through the head member 27a in a direction perpendicular to 
the second body 22, are disposed at respective positions upper right and 
left hand sides of the cut-out 44. A pair of elastic grinding wheels 27f 
and 27f are coaxially connected to the respective rotary shafts 46 and 46 
so as to be rotatable with respect to the head member 27a and to cause 
themselves to overlap the cut-out 44. More specifically, one of the 
grinding wheels 27f and 27f is fixed to that portion of the left rotary 
shaft 46 projecting from the side face, on which the motor 27b is mounted, 
of the head member 27a, whereas the other grinding wheel 27f is fixed to 
that portion of the right rotary shaft 46 projecting from the other side 
face of the head member 27a. Each of the grinding wheel is composed of 
numerous abrasive grains such as diamond grains bound together by a 
resilient bond made of synthetic resin such as urethane and polyurethane. 
Each of the rotary shafts 46 has a driven pulley 27e firmly fitting 
therearound. The driven pulley 27e of each rotary shaft 46 is operatively 
connected to the drive pulley 27c via a belt or wire 27d. 
The operation of the dressing apparatus thus arranged will now be 
described. 
At the outset, the dressing apparatus is mounted on the cutting machine 13 
having a cut-off wheel W which should be applied with a dressing 
treatment. As shown in FIG. 4, the cutting machine 13 includes, for 
example, an air bearing consisting of a hollow cylindrical inner member 48 
and ring-shaped outer member 49 coaxially disposed on the inner member so 
as to be rotated at a high speed about its axis. The outer member 49 has a 
ring-shaped clamp member (not shown) coaxially fastening the outer 
peripheral portion of the cut-off wheel W to the outer member 49. 
The mounting of the dressing apparatus is performed as follows. As shown in 
FIG. 4, the head member 27a of the dressing apparatus is inserted into the 
aperture 1 of the cut-off wheel W. Then, the magnet stand 15 is fixed to 
the end face of the inner member 48 of the cutting machine 13 so that the 
cut-out 44 of the head member 27a faces the inner peripheral cutting edge 
2 of the cut-off wheel W and the grinding wheels 27f and 27f are disposed 
adjacent, respectively, to the opposite side surfaces of the cutting edge 
2. The bolt 26 is turned to adjust the distance between the cutting edge 2 
and the grinding wheels 27f and 27f. In this state, the solenoid valve of 
the air cylinder 20 is open, and thereby the second body 22 is in its 
initial position where the guide roller 24 stays at the bottom of the 
V-shaped recess of the V block member 23. 
The cut-off wheel W is rotated by the cutting machine, and then, the drive 
motor 27b is turned on, to rotate the grinding wheels 27f and 27f. Next, 
the air cylinder 20 is actuated to cause either of the grinding wheels 27f 
and 27f to contact the cutting edge 2 of the cut-off wheel W. For example, 
as viewed in FIG. 4, when the right side surface of the cutting edge 2 of 
the cut-off wheel W should be dressed, the air cylinder 20 is extended, 
causing to move to the left, the first linear slider 17b, together with 
the second body 22. As the second body 22 is moved to the left, it is also 
moved downward under the guidance of the guide roller 24. More 
specifically, when the second body 22 is moved to the left, the guide 
roller 24 rolls up the slanting upper face of the V block member 23, 
resulting in the obliquely downward movement of the head member 27a. 
Consequently, the cutting edge 2 of the cut-off wheel is received in the 
cut-out 44 of the head member 27 a, and the right grinding wheel 27f is 
brought into contact with the right side surface of the cutting edge 2, 
resulting in the application of a dressing to the same surface of the 
cutting edge 2. On the other hand, when the left side surface of the 
cutting edge 2 should be dressed, the air cylinder 20 is retracted, 
causing the head member 27a to move to the right and also downward under 
the guidance of the guide roller 24. This oblique movement of the head 
member 27a results in the contact of the left grinding wheel 27f with the 
left side surface of the cutting edge 2 of the cut-off wheel W, and 
thereby the same surface of the cutting edge 2 is applied with a dressing. 
That is, it is possible in this dressing apparatus to selectively apply a 
dressing to either of the opposite surfaces of the cutting edge 2. 
Upon the dressing, since the bond used in the grinding wheels 27f and 27f 
is made of a resilient synthetic resin, either of the grinding wheels 27f 
and 27f deforms in such a manner that it contact both of the peripheral 
surface and one of the opposite side surfaces of the cutting edge 2 as 
shown in FIG. 6. Therefore, it is possible to simultaneously apply a 
dressing to both the peripheral and one of the opposite side surfaces of 
the cutting edge 2. Also, when the protruding abrasive grains 51, as shown 
in FIG. 7, of the grinding wheel 27f come into collision with the abrasive 
grains 2a of the cutting edge 2, the abrasive grains 51 retract in the 
resilient bond 52 and thereby the impact force due to the collision is 
dampened. Hence, these elastic wheels 27f and 27f help the cutting edge 2 
in the preventing damage such that the abrasive grains unnecessarily fall 
off the cutting edge even though the wheels 27f and 27f are pressed 
against the cutting edge 2 with an excess pressing force. Furthermore, 
when the abrasive grains 51 pass the abrasive grains 2a of the cutting 
edge 2, they protrude, again, from the surface of the bond 52 due to the 
resiliency of the bond 52 as shown in FIG. 8, and scrape the bond 2b among 
the abrasive grains 2a off the cutting edge 2. Accordingly, it is possible 
with this dressing apparatus to apply an efficient dressing treatment to 
the cut-off wheel by causing the grinding wheels 27f and 27f to directly 
contact the cutting edge 2. 
A displacement detecting sensor 53 which is disposed closely adjacent to 
the inner peripheral cutting edge 2 of the cut-off wheel W as shown in 
FIG. 9, may be mounted on the cutting machine 13 of the foregoing 
embodiment to detect a displacement of the cutting edge 2. This 
displacement detecting sensor 53 is such that it measures a displacement 
D, shown in FIG. 10, of one of the opposite side surfaces of the cutting 
edge which is cutting the silicon ingot 4, and supplies a signal 
representative of the measured displacement to a controller (not shown). 
The controller estimates a displacement, at the center of the silicon 
ingot 4, of the corresponding side surface of the cutting edge 2 on the 
basis of the measured displacement D and the data previously obtained 
through experiments utilizing a displacement measuring instrument such as 
one having three-point contact balls, and compares the estimated 
displacement with a preset value to determine a proper time to apply a 
dressing to the cutting edge 2. That is to say, if the estimated 
displacement of the cutting edge 2 exceed the preset value, the controller 
judges that one of the opposite side surfaces of the cutting edge 2 is 
dull, and operates the drive motor 27b and the air cylinder 20 to apply a 
dressing to the suitable side surface of the cut-off wheel W. 
FIGS. 11 and 12 illustrate another embodiment of the dressing apparatus in 
accordance with the present invention. In this embodiment, a connecting 
member 31 of a substantially rectangular block-like configuration is 
interposed between the head member 27a and the second body 22. The left 
edge portion of the connecting member 31 is secured to the right end 
portion of the head member 27a, while the lower right edge portion of the 
connecting member 31 is pivotally connected to the lower left end portion 
of the second body 22 for upward movement. A stopper plate piece 35 
extends horizontally from the second body along the lower edge of the 
connecting member 31 to normally retain the head member 27a extending 
parallel to the second body 22 as shown in FIG. 11 and to prevent the head 
member 27a from pivoting downward. Second urging means in the form of a 
coil spring 32 is interposed between the upper right edge portion of the 
connecting member 31 and the upper left end portion of the second body 22 
so as to allow the head member 27a to pivot upward when the head member 
27a is subjected to an external force directed upward and exceeding a 
predetermined value. Reference numerals 33 and 34 designate control levers 
which are attached to the bolt 18 and the screw 26 respectively for the 
convenience of the turning operation of the respective bolt 18 and screw 
26. When either of the grinding wheels 27f and 27f is brought into contact 
with the cutting edge 2 of a cut-off wheel, an impact force applied to 
both the grinding wheel 27f and the cutting edge 2 is dampened by the coil 
spring 32, and moreover, the pressing force with which the grinding wheel 
27f contacts the cutting edge 2 does not exceed the elastic force of the 
coil spring 32. Accordingly, both the cutting edge 2 of the cut-off wheel 
W and the grinding wheels 27f and 27f are protected from being damaged, 
and thus the service lives of both the cut-off wheel W and the grinding 
wheel are lengthened. 
In the foregoing embodiments, the dressing treatment is applied in such a 
state that the axis of either of the grinding wheels 27f and 27f is 
perpendicular to the axis of the cut-off wheel W when it is viewed from a 
plane of projection perpendicular to the direction in which the grinding 
wheel 27f and cut-off wheel W are alined. However, as shown in FIG. 13, 
the axes X.sub.1 and X.sub.2 of both the cut-off wheel W and the grinding 
wheel 27f may be inclined at an angle smaller than 90.degree. to each 
other when they are viewed from the aforementioned plane of projection. 
FIGS. 14 and 15 illustrate a further embodiment of a dressing apparatus, 
which is able to achieve such an angular relationship between the axes of 
the respective grinding and cut-off wheels. In FIGS. 14 and 15, the head 
member 60 is pivotally connected via a pivot 57 to the second body 22 for 
movement about a vertical axis, i.e., an axis parallel to the first rod. 
Suitable fastening means such as a thumbscrew (not shown) is provided on 
the connection between the head member 60 and the second body 22 to 
restrain the pivotal movement of the head member 60. That is, by pivoting 
the head member 60 with respect to the second body 22, it is possible to 
cause the axes of the grinding wheel 27f to incline at a desired angle to 
the axis of the cut-off wheel W. Furthermore, as shown in FIG. 16, the 
axes X.sub.1 and X.sub.2 of the respective grinding and cut-off wheels 27f 
and W may be inclined at an angle .theta..sub.2 to each other when they 
are viewed from a plane of projection parallel to both the axis X.sub.2 of 
the cut-off wheel W and the direction in which the grinding wheel 27f and 
the cut-off wheel W are aligned. To practice such an inclination, the head 
member 60 in this embodiment is connected to the second body 22 for 
rotation about a horizontal axis perpendicular to the rotary shaft 46. 
More specifically, as shown in FIGS. 14 and 15, the head member's first 
portion in the form of a block 54 of a suitable configuration is pivotally 
connected to the left end of the second body 22 for movement about the 
pivot 57, and the head member's second portion 56 is connected to the 
first portion 54 via shaft 58 for rotation about a horizontal axis 
perpendicular to the rotary shaft 46. Suitable means such as a thumbscrew 
(not shown) is also provided on the connection between the first and 
second portions 54 and 56 of the head member 27a. 
An embodiment of a dressing method in accordance with the present invention 
which utilizes the dressing apparatus of the third embodiment arranged as 
disclosed above will now be described. 
The grinding wheel 27f is brought into contact with the cutting edge 2 of 
the cut-off wheel in the state as shown in FIG. 13. That is, in FIG. 13, 
the grinding wheel 27f and the cut-off wheel W are aligned in a direction 
perpendicular to the surface of the drawing paper, and the axis X.sub.1 of 
the grinding wheel 27f is inclined at an angle .theta..sub.1 to the axis 
X.sub.2 of the cut-off wheel W. The angle .theta..sub.1 is larger than 
0.degree. and smaller than 90.degree.. Needless to say, both the grinding 
wheel 27f and the cut-off wheel W are restrained so as not to be axially 
movable. When the cut-off wheel W is driven to rotate about its axis 
X.sub.2, a component Fr, which is directed perpendicularly to the axis 
X.sub.1 of the grinding wheel 27f, of the torque F of the cut-off wheel W 
is transmitted to the grinding wheel 27f, resulting in the rotation of the 
grinding wheel 27f. On the other hand, a component Fs, which is directed 
parallel to the axis X.sub.1 of the grinding wheel 27f, of the torque F 
causes a scraping between the grinding wheel 27f and the cut-off wheel W, 
thereby a dressing is applied to the cutting edge 2 of the cut-off wheel 
W. When the angle .THETA..sub.1 is 0.degree., the component Fs causing the 
scraping is not generated. As the angle .theta..sub.1 becomes larger, a 
greater scraping is caused, and thus a greater dressing is applied to the 
cutting edge 2. In other words, it is possible to control the level of a 
dressing treatment by adjusting the angle .theta..sub.1 between the axes 
of the grinding wheel 27f and the cut-off wheel W. In addition, it should 
be readily apparent that the grinding wheel 27f may be driven instead of 
the cut-off wheel W, and otherwise both the cut-off wheel W and the 
grinding wheel 27f may be driven. 
Although in the foregoing embodiments, the dressing apparatus and the 
dressing method is utilized for applying a dressing to the inner 
peripheral cutting edge of a cut-off wheel, it should be readily apparent 
that they may be utilized for a cut-off wheel which has an outer 
peripheral cutting edge requiring an application of a dressing. A pair of 
a guide roller connected to the second body and an inverted V block-shaped 
member connected to the first body 17a may be employed instead of the pair 
of the guide roller 24 and the V block member 23 of the foregoing 
embodiments.