The present invention relates generally to a tool holder assembly
as defined in the preamble of claim 1 and 5 and more particularly to a means for
radially locating and axially locking the position of the tool holder with respect
to a tool support member.
Tool holders are known which include long cylindrical or tapered
shanks which insert into an axial bore of a tool support member. The tool holder
is typically secured by means of a set screw which screws into engagement with
the tool shank. The set screw sometimes includes a bevelled or faceted end which
engages with an inclined surface on the shank of the tool holder so that when the
screw is tightened, the tool holder is pulled rearwardly against the support member.
One problem associated with these types of tool holders is that they
do not give repetitive and accurate radial location between the support member
and tool holder. In the past, tool holders have been located by providing a keyway
in either the tool shank or the tool shank bore which cooperates with key element
in the other member. Another method which has been tried is to provide one or more
flat surfaces on the tool shank which are engaged by the ends of the set screw.
In each of the above cases, the accuracy and repeatability of the radial location
between the two parts is not as desired.
GB-A 924 885 representing the closest prior art discloses a tool
support member having a cylindrical bore formed for receiving a shank of a tool
holder. A conical recess is formed in the shank of a tool holder and is adapted
to be engaged by a conical nose of a locator screw. The conical recess formed is
set off-center from the axis of a locator screw hole. Thus, a line contact between
the conical end of the locator screw and the conical recess is achieved. By threading
the locator screw into a locator screw hole to generate the line contact between
the conical recess and the conical end, an axial force which tends to seat the
tool holder in a tool support member is produced. Therefore, the support member
and the tool holder are substantially fixed to each other by a produced frictional
US-A-4,575,292 discloses a device incorporating an automatically
centered drive pin for the transmission of torque. The device is provided for connecting
two tool parts of a tool system. One tool part includes a boring head which has
a cylindrical spigot with a cylindrical transverse bore and, at an approximate
right angle, a conical transverse bore. The drive pin, which is supported within
the cylindrical transverse bore, has ends that extend beyond the diameter of the
cylindrical spigot. The second tool part includes a connecting shaft with a bore,
horizontally opposed recesses extending along the bore, and a threaded bore for
receiving a retaining screw. The horizontally opposed recesses which become narrow
in the radially outward direction receive the ends of the drive pin. When a conical
turned end of a retaining screw engages the conical transverse bore, a shoulder
of the cylindrical fastening spigot tightens against a corresponding face of the
connecting shaft. In a loaded condition, the drive pin automatically centers to
evenly distribute the developed forces from the ends of the drive pin to the horizontally
The present invention as defined in claims 1 and 5 provides a mechanism
that will provide accurate and repeatable radial location between a tool holder
or internal mechanism and tool support member. In addition, the present invention
will produce an axial force to lock the tool holder or other tool part against
the tool support member.
In one embodiment, the present invention includes a tool support
member which terminates in an end face. An axial bore extends rearwardly from the
end face of the support member. The wall of the support member surrounding the
axial bore is formed with a locator screw hole that extends normal to the axis
of the tool holder. A locator screw is threaded into the locator screw hole and
includes a conical nose.
The tool holder includes a forward portion formed with a tool receiving
pocket, and a shank extending rearwardly from the forward portion. The shank is
formed with a forwardly facing conical abutment surface which forms of a cone segment
of not more than 180 degrees. The axis of the conical abutment surface is perpendicular
to the axis of the tool holder and aligns with the axis of the locator screw hole
in the support member. The conical abutment surface cooperates with the conical
nose section of the locator screw to firmly lock the tool holder against the support
member when the locator screw is tightened. Additionally, because the size and
angle of the conical nose section corresponds to the conical abutment surface
in the shank, these elements also cooperate to radially locate the tool holder
with respect to the support member.
In the preferred embodiment of the invention, the locator screw hole
includes a non-threaded portion. The locator screw includes a guide member which
fits snugly in the non-threaded portion of the locator screw hole. The hole and
the guide member cooperate to remove slop caused by thread pitch misalignment
assuring repetitive and accurate radial location between the tool holder and support
A second embodiment of the invention employs the radial locator in
connection with an internal clamping mechanism. The internal mechanism includes
a generally cylindrical stub member. The stub member is also formed with a forwardly
facing, conical abutment surface. The conical abutment surface of the stub member
is engaged by a locator screw as in the first embodiment, to radially locate the
stub member with respect to the support member.
Additional embodiments of the invention will become readily apparent.
For instance, the invention may be used to secure an end mill in an end mill holder.
These additional embodiments are also embraced within the claims.
Accordingly, it is a primary object of the present invention to provide
a mechanism for securing a tool holder or other tool part to a support member
which gives repetitive and accurate radial location between the two parts.
Another object of the present invention is to provide a mechanism
for securing a tool holder or other tool part to a support member which provides
positive axial locking between the two parts.
Another object of the present invention is to provide a tool holder
assembly which allows rapid interchange of one tool holder for another.
Other objects and advantages of the present invention will become
apparent and obvious from a study of the following description and the accompanying
drawings which are merely illustrative of such invention.
- Figure 1 is a perspective view of the tool holder assembly of the present invention
with a fragment removed to illustrate the locator screw.
- Figure 2 is a perspective view of the tool holder used in connection with the
- Figure 3 is an elevation of the rear end of the tool holder of the first embodiment;
- Figure 4 is a section view of the first embodiment;
- Figure 5 is a perspective view of a second embodiment of the invention with
a fragment of the support member removed to illustrate the invention;
- Figure 6 is a perspective view of the tool holder and stub member used in connection
with the second embodiment.
- Figure 7 is a partial section view of the tool holder assembly of the second
Referring now to the drawings, the tool holder assembly 10 of the
present invention is shown. In its simplest form, the tool holder assembly 10
includes a tool holder 12 and a support member 14. In the illustrated embodiment,
the tool holder 12 comprises a boring bar, although the present invention is not
limited thereto. For instance, the present invention may be utilized to secure
a part of an internal clamping mechanism as shown in Figures 5-7, or to secure
an end mill in its holder.
Referring back to the embodiment shown in Figures 1 through 4, the
tool holder 12 includes a forward portion 16 and a rearwardly extending shank 18.
The forward portion 16 is formed with a pocket 20 adapted to receive a cutting
tool. The pocket 20 is conventional in design and is adapted to receive an indexable
cutting insert 22, shim 24, and locking pin 26.
The shank 18 extends rearwardly from the forward portion 16. A rearwardly
facing shoulder 28 is formed at the juncture of the forward portion 16 and shank
18. Preferably, the rearwardly facing shoulder is planar and is oriented at 90
degrees to the longitudinal centerline of the shank 18.
An annular recess 30 is formed in the shank 18 adjacent a rear end
portion 32. The annular recess 30 extends circumferentially around the shank 18.
It is appreciated that the annular recess 30 can be substituted by a recessed
pocket without departing from the spirit and essential characteristics of the
A hole 36 is drilled in the shank 18 which lies partly within the
annular recess 30 and partly on the rear end portion 32 as best seen in Figure
3. The axis of the hole 36 is normal to the longitudinal centerline of the tool
holder 12. It is preferred that slightly more than one-half of the hole 36 lies
in the annular recess 30 as best shown in Figure 4. In other words, the centerline
of the hole 36 lies within the annular recess 30 closely adjacent the rear wall
The portion of the hole 36 lying on the rear end portion of the shank
18 is countersunk so as to form a forwardly-facing, conical abutment surface 38.
The conical abutment surface 38 forms an angle of approximately 60 degrees with
respect to the centerline of the hole 36. Also, since the centerline of the hole
36 lies within the annular recess 30, the abutment surface 38 forms a cone segment
of slightly less than 180 degrees. The centerline of the hole 36 and conical abutment
surface 38 are on the same centers.
The support member 14 includes a forward portion 50 and a tapered
rear portion 52. The rear portion 52 is adapted to insert into a conical pocket
of a machine spindle (not shown). The forward portion 50 includes an end face
54. A tool shank bore 56 extends axially from the end face 54 towards the rear
portion 52. The tool shank bore 56 is of the same dimension as the tool shank
18 of the tool holder 12 to provide a close fit between the two parts.
Within the wall structure 58 surrounding the bore 56 is formed a
locator screw hole 60. As shown in Figure 4, the locator screw hole 60 includes
a nonthreaded portion 66 and a threaded portion 68. See Figure 4. The threaded
portion 68 is larger in diameter than the non-threaded portion 66 so as to define
a shoulder 70 between the larger and smaller diameters.
Means are provided for axially locating the tool holder 12 with respect
to the support member 14. The axial locating means in this embodiment comprises
the rearwardly facing shoulder 28 of the tool holder which butts against the end
face 54 of the support member 14. When the tool holder 12 is located axially,
the centerlines of the conical abutment surface 38 and locator screw hole 60 should
preferably lie in the same axial plane.
A locator screw 72 is threaded into the locator screw hole 60 for
securing the tool holder 12 within the support member 14. The locator screw 72
includes a threaded portion 74 adapted to engage with the threaded portion 68
of the locator screw hole 60 and a nonthreaded guide portion 76. The guide portion
76 is so sized as to fit snugly within the non-threaded portion 66 of the locator
screw hole 60. Thus, guide portion 76 of the locator screw 72 acts as a pilot
during assembly and removes slop between the locator screw hole 60 and locator
screw 72 caused by thread pitch misalignment.
The guide portion 76 of the locator screw 72 terminates in a conical
nose 78. The angle of the conical nose 78 corresponds to the angle of the conical
abutment surface 38 of the tool holder 12. Further, the radius of the conical
nose 78 at its widest and smallest points is the same as the radius of the conical
abutment surface 38. Because the conical nose piece 78 is so sized and dimensioned,
it will engage fully with the abutment surface 38 in the tool holder 12. Thus,
when the screw 72 is tightened against the tool holder 12, the tool holder 12 will
rotate until the centerline of the conical abutment surface 38 aligns with the
centerline of the locator screw 72. Thus, the cooperation of the adjusting screw
72 with the conical abutment surface 38 in the tool holder 12 makes the tool holder
12 selfcentering and assures repetitive and accurate radial location between the
tool holder 12 and support member 14. In addition the locator screw 72 cooperates
with the abutment surface 38 to lock rearwardly facing shoulder 28 of the tool
holder against the end face 54 of the support member 14.
The single locator screw 72 provides accurate radial location . However,
one or more conventional set screws 64 may be provided which extend through set
screw holes 62 in the support member 14. The set screws 64 do not provide radial
location, but rather, provide more positive axial location.
Referring now to Figures 5 through 7, a second embodiment of the
present invention is shown and indicated generally by the numeral 100. The second
embodiment of the invention employs the radial locator to secure a part of an
internal clamping mechanism 106 within the axial bore of a support member 104.
The radial locator assures accurate radial location between the clamping mechanism
106 and the support member 104.
The second embodiment includes a tool holder 102, support member
104 and internal clamping mechanism 106. The tool holder 102 includes a forward
portion 108 and a tapered shank portion 110. As in the first embodiment, the forward
portion 108 is formed with a pocket 112 adapted to receive a cutting tool.
The tapered shank 110 extends rearwardly from the forward portion
108. A rearwardly facing shoulder 114 is formed at the juncture of the shank with
the forward portion 108. The shoulder 114 is adapted to engage the end face 120
of the support member 104. Preferably, the shoulder 114 is planar and is oriented
90. to the longitudinal centerline of the shank 110.
The tubular shank 110 has a frusto-conical shape. A pair diametrically
opposed apertures 116 are formed in the wall of the tubular shank 110 which extend
from the inner surface thereof to the outer surface. Two diametrically opposed
slots 118 extend from the rear end of the tubular shank and serve as keyways.
The slots 118 accept keys 127 formed on a stub member 124 to hold the tool holder
non-rotatable with respect to the stub member 124. This type of tool holder is
disclosed more fully in US-A 4,723,877.
The support member 104 includes an end face 120. Tapered bore 122,
which is adapted to receive the tapered shank 110 of the tool holder 102, extends
axially from the end face 120. The clamping mechanism 106 is contained within
the bore 122 and butts against the bottom thereof.
The clamping mechanism 106 includes a hollow stub member 124 having
diametrically opposed apertures 126. Between the apertures 126 are raised portions
127 which serve as keys. The raised portions 127 insert into the slots 118 of
the tubular shank to prevent relative rotation between the stub member 124 and
the tool holder 102.
Two spherical balls 128 are contained within the stub member 124.
(See Figure 7) The balls 128 are urged outwardly through the apertures 126 by a
locking rod 130. The locking rod 130 is formed with ball driving ramps 132 which
drive the balls 128 outwardly when the locking rod 130 is pulled rearwardly. As
the locking balls 128 are driven outwardly by ramps 132, they are driven into
abutment with the walls of the apertures 116 in the tool holder shank 110 as best
seen in Figure 7. In this manner, a rearward force is directed against the tool
holder 10 such that the rearwardly facing shoulder 114 is pulled against the end
face 120 of the support member 104.
The radial location of the tool holder 102 in the second embodiment
is dependant upon the radial location between the stub member 124 and support member
104. Thus, the second embodiment incorporates the radial locator into the stub
An annular recess 140 extends circumferentially around the rear end
142 of the stub member 124. As in the first embodiment, a hole 144 having a centerline
perpendicular to the longitudinal centerline of the stub member 124 is formed in
the stub member 124. The hole 144 lies partly within the annular recess 140 and
partly on the rear end portion 142. The portion lying on the rear end is countersunk
to form a conical abutment surface 146.
As in the first embodiment, the support member 104 includes a locator
screw hole 150 extending through the wall surrounding the bore 122. In this embodiment,
accurate axial location is provided by butting the rear end portion 142 of the
stub member against the bottom of the axial bore 122. Thus, the centerline of
both the locator screw hole 150 and conical abutment surface 146 lie in the same
The locator screw hole 150, as in the first embodiment, includes
threaded and non-threaded portions 152 and 154. Similarly, the locator screw 160
includes a non-threaded portion 164 and a threaded portion 162. The non-threaded
portion 164 terminates in a conical nose 166. The angle of the conical nose corresponds
to the angle of the conical abutment face 146. Further, the radius of the conical
nose 166 at its widest point and smallest point is the same of the radius of the
conical abutment surface 146 at its widest point and smallest point. Thus, full
circular face-to-face contact between the conical nose 166 and the conical abutment
surface 146 is assured for less than 180 degrees.
The locator screw 160 is threaded into the locator screw hole 150
within the support member 104. When the locator screw 160 is turned in a first
direction, the conical nose 166 moves into engagement with the conical face 146
on the stub member 124. Because the angle and radius of the conical face 146 is
the same as the angle of the radius of the conical nose 166, full circular face-to-face
contact between those parts for less than 180 degrees is obtained. As a result,
the tightening of the locator screw 160 against the conical face 146 of the tool
holder 102 will cause the stub member 124 to automatically rotate to a predetermined
radial position. At the same time, the conical nose 166 cooperates with the conical
face 146 to seat the stub member 124 against the bottom of the bore 122. Once
the stub member 124 is secured within the bore 122, the tool holder 102 can be
inserted into the bore 122 and secured by pulling the locking rod 130 rearwardly.
From the foregoing, it is apparent that the present invention provides
a mechanism for securing a tool holder or other tool part to a support member
which gives accurate and repetitive radial location between the two parts. Further,
the present invention provides positive axial locking.
The present invention may, of course, be carried out in other specific
ways than those herein set forth without parting from the spirit and essential
characteristics of the invention as claimed. The present embodiments are, therefore,
to be considered in all respects as illustrative and not restrictive, and all
changes coming within the meaning of the appended Claims are intended to be embraced