Grinding head for a machine for grinding helically grooved cutting tools

A grinding head for a tool grinding machine is used for grinding helically grooved cutting tools. The grinding head includes a rotatable spindle supported by adjustable carriages or slides so that it can be reciprocated along one axis and pivoted about another axis perpendicular to the one axis. Further, it can be pivoted about a third axis disposed perpendicularly to the another axis. The adjustable carriages are supported on a carrier of a grinding head column so that the grinding head can be displaced about a pivot point for adjusting the head to the diameter of the tool being grooved and for adjusting the rake angle about the pivot point.

BACKGROUND OF THE INVENTION 
The present invention is directed to a grinding head used in a machine for 
grinding helically grooved cutting tools. The grinding head includes a 
rotatable spindle with carriages supporting the spindle so that it can be 
displaced about a pair of perpendicular axes. The grinding head can be 
reciprocated along one axis and it can be pivoted about another axis. 
In a known universal tool grinding machine in addition to the vertically 
arranged grinding head carrier, a grinding table is used for supporting 
the tool carrier and the grinding table is supported so that it can be 
pivoted about a vertical axis while the table moves reciprocally or back 
and forth in the horizontal direction. The grinding table supports the 
grinding head carrier. The workpiece to be ground is adjusted by the tool 
carrier with reference to a grinding disc so that the surface to be ground 
coincides with a horizontal pivot axis of a surface plate defined by a 
stop projection. The grinding disc is adjusted by carriages or slides so 
that it contacts the surface of the workpiece to be ground before the 
grinding process can be carried out. If the grinding disc in such a 
grinding head is adjusted to the helix angle of the cutting tool, the 
working point of the grinding disc moves out of the axial center and 
intersects the cutting tool perpendicularly relative to the rotational 
axis during subsequent grinding, since the grinding disc can be moved 
along the vertical Z-axis of the grinding head during the grinding 
operation. Accordingly, a desired rake angle can be achieved only by 
approximation of simultaneous adjustment in the direction of the Z and Y 
axes. Previously, the extent of the adjusting motions were determined only 
by sample grinding of a cutting tool and taking subsequent measurements 
and making repeated corrections in the adjusting values. In other words, 
if the forward feed movement of the carriages must be adjusted to the 
diameter of the tool to be ground, but are referred to the axial center of 
the tool in the previously known arrangement, the rake angle of helically 
grooved cutting tools can be ground only in an approximate manner in such 
a tool grinding machine. Further, varying rake angles are produced in the 
cutting tool in numerically controlled grinding operations. 
SUMMARY OF THE INVENTION 
Therefore, the primary object of the present invention is to provide an 
improvement of the grinding head of the previously known grinding machine 
so that the grinding of the rake angle of helically grooved cutting tools 
can be effected by a single adjusting movement along a single axis of the 
carriage mounting the grinding disc based on the center of the cutting 
tool and its diameter for effecting a linear contact between the face of 
the cutting tool and the grinding disc so that the adjusting movement of 
the grinding disc does not change the rake angle of the cutting tool. 
In accordance with the present invention, a further axis for adjusting the 
rake angle is provided with such axis being adjustable perpendicularly to 
the diameter of the cutting tool and with the grinding head being 
securable in the adjusted position. 
In accordance with the positioning of the grinding head according to the 
present invention, the adjustment of the rake angle is effected about a 
pivot axis which, in turn, is adjustable relative to the diameter of the 
tool being ground, whereby the originally adjusted rake angle is retained 
during the adjusting movement of the grinding disc In this manner the 
grinding of a desired rake angle in a helically grooved cutting tool can, 
for the first time, be accurately reproducible, for example according to 
scale, and for the first time can be automated. Distortions in the ground 
surface, for example in conical cutting tools, can be compensated, since 
the pivot axis can be readjusted during grinding, such as by the use of 
stepping motors. Another advantage is that the sharpening of the grinding 
disc which is true to the desired shape can be provided by the same 
adjusting means. 
A grinding head is known from the German Patentschrift No. 920 050 in which 
the spindle carrying the grinding disc is mounted in a shaft support which 
can be pivoted around an axis intersecting the spindle axis at a right 
angle with the shaft support carried by a forward feed carriage which can 
be reciprocated along a horizontal axis. The forward feed carriage can be 
mounted on a cross-piece for pivotal movement around a vertical axis and 
the cross-piece can be pivoted around a horizontal axis whereby the 
cross-piece is supported by a carriage for reciprocal movement at a 
vertical surface plate which, in turn, can be rotated about the horizontal 
axis to enable the desired adjusting movements of the grinding disc in 
accordance with a desired clearance angle of the workpiece being ground. 
Regardless of the face that only the clearance angle at the front side of 
the so-called cutter heads can be ground by this grinding head so as to be 
true to shape, the carriage supporting the grinding spindle can be pivoted 
only around a stationary axis and, therefore, can not be adjusted to the 
axial center of a helically grooved cutting tool or to its diameter. In 
such a construction the same rake angle errors occur during the grinding 
of helically grooved cutting tools as were mentioned above. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its use, reference 
should be had to the accompanying drawings and descriptive matter in which 
there are illustrated and described preferred embodiments of the 
invention.

DETAILED DESCRIPTION OF THE INVENTION 
In the drawing, a tool grinding machine 7 is mounted on a support 6, not 
shown in detail, and includes a carriage bed 8 for an elongated carriage 9 
and a vertically adjustable grinding head column 13 acting as a carrier 
for the grinding head 15. The grinding head column 13 includes an angled 
supporting arm 11, note FIG. 3. 
A head stock 16 and a corresponding tailstock 17 are supported on the 
elongated carriage 9 and are arranged to support a workpiece to be ground. 
The workpiece is a so-called spiral-fluted cylindrical cutter or roll 
cutter 20 mounted on a spindle 19 and held between the head stock and the 
tailstock. Drives, not shown, which can be numerically controlled, 
reciprocate the head stock 16 and tailstock 17 for the workpiece so that 
the workpiece can be reciprocated in the direction of the arrows WL.sub.1 
and WL.sub.2 along an axis X.sub.1 and can also be rotated about the axis 
in the direction of the arrows WD.sub.1 and WD.sub.2. Grinding head 15 has 
a spindle 22 rotatably supported on an adjustable carriage 21 and a 
grinding disc 23 for the respective workpiece is mounted on the spindle. 
The grinding disc 23, as shown in FIG. 2, has a angle of inclination K of 
its radially outer annular part surface relative to the planar central 
part. The carriage 21 moves back and forth or reciprocates in the 
direction of arrows LY.sub.1, LY.sub.2, note FIG. 2, along an axis 
Y.sub.2. The carriage 21 is supported on an angularly pivotal carriage 25 
so that it can be rotated around an axis X.sub.2 in the direction of the 
arrows XD.sub.1 and XD.sub.2 and intersects the point D.sub.3. The 
pivotally displaceable carriage 25 is supported by a cross arm 26 mounted 
on arm 24 extending transversely of an adjustable carriage 27 so that it 
can be pivoted around an axis Z.sub.2 in the direction of the arrows 
ZS.sub.1 and ZS.sub.2 with the axis Z.sub.2 intersecting the point 
D.sub.4. The adjustable carriage 27 is supported for movement upwardly and 
downwardly in a carriage guide 29 in the direction of the axis Z.sub.2'. 
The carriage guide 29 is arranged to be pivoted about a pivot point 
D.sub.2 formed by a spring pin 10 mounted in the supporting arm 11 in a 
semi-circular groove 14, note FIG. 2, located in the arm 11 of the 
grinding head column 13 so that it can be pivoted relative to the axis 
Z.sub.2 in the direction of the arrows ZS.sub.3 and ZS.sub.4. The carriage 
guide 29 can be secured in the selected adjustable position by a T-screw 
or capstan-head screw 18. 
Grinding head column 13 is supported for movement along an axis Z.sub.1 so 
that it can be moved up and down, as mentioned above, for reciprocation in 
the direction of the arrows SKS.sub.1 and SKS.sub.2 and also along an axis 
Y.sub.1 in the support 6 for movement in the direction of the arrows 
SKS.sub.3 and SKS.sub.4. 
With the arrangement of the different carriages and their supports as well 
as their adjustability, it is possible to align the grinding disc 23 with 
the axis X.sub.1 which extends through the axial center D.sub.1 of the 
tool to be ground and also with the point D.sub.2 located on the diameter 
of the tool being ground so that the point D.sub.2 is positioned 
vertically above the axis X.sub.1 with the point D.sub.2 located along an 
axis extending through the point D.sub.2 defined by the pin 10 and 
corresponding to the desired rake angle of the tool to be ground. The 
adjustment effected by pivoting in the direction ZS.sub.3 and ZS.sub.4 of 
the carriage guide 29 is secured by tightening the T-screw 18. Further, 
grinding disc 23 can be pivoted around the point D.sub.3 on the axis 
Y.sub.2, for corresponding its angle of inclination radially outer annular 
part surface to the point D.sub.2 and aligned with the axis Z.sub.2, by 
means of pivotally displaceable carriage 25, note FIG. 2, that is, by 
pivoting the disc 23 by means of the carriage 25. Only after these 
adjustments are made, the grinding disc is driven in the usual manner over 
the adjustable carriage 27 to produce the desired cutting surface. 
Accordingly, the axis Z.sub.2', as shown in FIG. 2, is the corrected 
adjustable axis corresponding to the rake angle to be produced. 
As can be seen in FIG. 2, the point D.sub.2 is the intersection between the 
axes A.sub.1 and Z.sub.2 with the axis Al intersecting the center point 
D.sub.1 of the tool 20 to be ground, while the axis Z.sub.2 intersects the 
pivot point D.sub.4 for the adjustment of the angle of slope corresponding 
to the slope of the helical grooves in the tool 20, the point D.sub.3 for 
the adjustment of the surface with the angle of inclination K of the 
grinding disc 23, and the point D.sub.2 forming the pivot point for the 
adjustable carriage 29, accordingly, these axes define the rake angle of 
the tool 20 to be ground. The annular part surface of the grinding dis 23 
is at the angle of inclination K to the planar central part of the disc. 
As a result, grinding disc 23 is supported to be pivoted around another 
axis Z.sub.2', (pivot point D.sub.2), located in the neutral position so 
as to be axially parallel with the axis Z.sub.1 while it is supported to 
be rotatable (rotating point D.sub.4) only around axis Z.sub.2 by means of 
the carriages 21, 24, 26, 27 and 29. Moreover, the grinding disc is 
adjustable around the axis Y.sub.2 for correcting its angle of taper, that 
is, around pivot point D.sub.3. 
Further, as is known, the spacing of the axes Z.sub.1 and A.sub.1, note 
FIG. 2, as well as the spacing of the pivot points D.sub.1 and D.sub.2, 
note FIG. 1, can be checked by means of guides fixed on the machine frame 
which guides may carry markings readable electronically or 
opto-electronically for the purpose of numerical control of the grinding 
head. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the inventive principles, it 
will be understood that the invention may be embodied otherwise without 
departing from such principles.