Tool holder for inserts

A clamp for indexable inserts used especially for turning. The clamp consists essentially of a clamp shaft and a clamp head combined with it in one piece. The clamp shaft can be secured to an axis-parallel clamping surface of a tool holder by a supporting surface obliquely transfixed by a clamping screw. The clamp head has an open-edged recess to take the indexable insert, one effective cutting corner of which projects on one side beyond the outer surface away from the support surface. In order to be able to adjust the distance between the clamping surface and the cutting corner, the clamp head has, in the free region between the recess, the supporting surface and the clamp shaft, a slot-like aperture having a curved cross-sectional shape open towards the clamp shaft. The clamp head can be elastically bent with respect to the clamp shaft under the effect of an adjuster.

FIELD OF THE INVENTION 
The invention relates to a tool holder for inserts, particularly indexable 
throwaway inserts, having a holder shank, which can be fastened to an 
axis-parallel clamping face of a tool carrier with a contact face being 
passed through, preferably obliquely, by a tightening screw. The tool 
carrier preferably configured as a boring bar, having a holder head, which 
is formed on the front side onto the holder shank and which includes a 
recess open at the margin for the reception of the insert which is aligned 
essentially perpendicular to the contact face and protrudes on one side 
with an active tool nose beyond the outer face that is facing away from 
the contact face, and having a device for adjusting the distance between 
the clamping face and the active tool nose. 
BACKGROUND OF THE INVENTION 
In known tool holders of this type (Cartridges type A for indexable 
throwaway inserts according to DIN 4985), which are clamped in a tool 
carrier with one or two fastening screws extending through an oblique 
elongate hole in the holder shank, there is provided a cross-setting screw 
for the adjustment of the distance between the clamping face and the 
active tool nose, which setting screw extends through an internal thread 
of the holder head and is supported with its tip against the clamping face 
of the tool carrier. The handling involved in carrying out the adjustment 
here is extremely awkward since, first of all, the fastening screw has to 
be loosened, then the cross-setting screw adjusted in the desired 
direction and finally the fastening screw re-tightened. This adjustment 
has to be repeatedly performed, where necessary, until the desired measure 
is exactly set. Further, it is considered a drawback in this adjusting 
operation that the setting angle of the insert is altered upon the 
adjustment of the distance measure, which is particularly disadvantageous 
where exactly defined shoulders are intended to be turned. Added to this 
is the fact that the cartridge does not bear with its contact face 
squarely upon the clamping face of the tool carrier, but rather, in 
forming a gap, a clamping triangle is created, the rigidity and damping 
characteristics of which often leave a lot to be desired, particularly in 
heavy-duty machine-cutting operations. The cross-setting screw is 
relatively small and consequently has only a small, keytype engagement, 
which is vulnerable to wear, and a small end face inclined toward the 
notch in the tool body. 
Starting from this basis, the object of the invention is to provide a tool 
holder of the type stated in the introduction, which, when the fastening 
screw is fastened, can be adjusted in its distance measure between the 
clamping face and tool nose, simply and without adjustment of the setting 
angle. 
In order to achieve this object, the combination of features specified in 
patent claim 1 is provided. Advantageous designs and refinements of the 
invention derive from the dependent claims. 
SUMMARY OF THE INVENTION 
The solution according to the invention is based upon the concept that the 
holder shank can be clamped rigidly in the tool carrier and that the 
holder head, by the introduction of suitable predetermined bending points, 
is elastically bendable in the desired direction, relative to the holder 
shank, with the aid of a control member. In order to achieve this, the 
following combination of features is proposed according to the invention: 
the holder head, in the free region between recess, contact face and holder 
shank, is provided with a gap-shaped aperture which passes through 
parallel to or obliquely to the contact face and which exhibits an 
arc-shaped cross-sectional contour which is open toward the holder shank 
and is limited by two spaced apart aperture ends enclosed in the holder 
head material, one of the aperture ends being disposed close to the 
contact face and the other aperture end being disposed close to the outer 
face of the holder head, in each case forming a thin-walled material 
bridge; 
the holder head, in the region of the two material bridges, being 
elastically bendable relative to the holder shank, under the influence of 
a control member, essentially perpendicular to the contact face. 
The aperture ends herein are preferably disposed close to the holder shank, 
preferably in a plane perpendicular to the contact face. The bending zones 
at the aperture ends thereby form a type of articulated parallelogram, 
which ensures an inclination-free distance adjustment. 
In the case of a tool holder in which the holder head, on the side lying 
opposite the contact face, protrudes in a step shape beyond the holder 
shank, it is preferable if the aperture end lying close to the outer face 
is disposed in the protruding part of the holder head. 
Advantageous designs of the invention envisage: 
that the aperture includes a gap segment located on the outer side, which 
gap segment lies preferably parallel to the contact face and is limited on 
the inner side by a flank of a shank-fixed extension arm; 
that the aperture includes a gap segment located on the contact face side, 
which gap segment lies preferably parallel to the contact face and is 
limited by a flank of the shank-fixed extension arm; 
that the gap segment located on the outer face side is connected to the gap 
segment located on the contact face side via a shank-remote, preferably 
arc-shaped transverse segment, limited by an end flank of the shank-fixed 
extension arm; 
that the gap segment located on the contact face side is limited on the 
shank side by the aperture end lying close to the contact face; 
that the gap segment located on the outer face side is adjoined by an 
oblique segment running obliquely to the shank side and in the direction 
of the outer face and limited by the aperture end lying close to the outer 
face. 
In consideration of these measures, the control member is able to be 
realized differently, namely: 
by a setting screw which can be actuated from the outer face of the holder 
head, is guided in an internal thread of the holder head essentially 
perpendicularly to the contact face, penetrates the gap segment located on 
the outer face side and can be pressed with its preferably flattened end 
face against the shank-fixed extension arm; 
by a setting screw which reaches from the outer face through the holder 
head and can be pressed with its end face against the clamping face of the 
tool carrier and which preferably extends transversely through the 
extension arm and the two gap segments and is guided either within an 
internal thread located directly in the holder head or in the internal 
thread of a threaded bushing, which threaded bushing is inserted from the 
contact face into a recess of the holder head in twist-proof securement 
and is supportable against a stop of the holder head; 
by a setting screw which can be actuated from the end face of the holder 
head, is guided by an internal thread of the holder head essentially 
parallel to the contact face, penetrates the transverse segment of the 
aperture and can be pressed with a conical part of its tip against the 
oblique or arc-shaped end flank of the shank extension arm; 
by a control member which is guided in a slideway or threaded guide of the 
tool carrier and can be pressed with a force component, in the direction 
of adjustment, against the tool head; 
by a setting screw which is guided in a preferably radially or axially 
aligned internal thread of the tool carrier and is provided, where 
necessary, with a conical tip; 
by a control body which is guided in a preferably radial slideway of the 
tool carrier and can be actuated by means of a wedge gearing disposed in 
the tool carrier and preferably including a control rod with a wedge 
bevel. 
In order, to enable a defined and reproducible distance adjustment by 
simple means, a scale graduation is provided in the region of the setting 
screw head. 
In order to stiffen the clamping connection between tool holder and tool 
carrier, it is advantageous if the gap-shaped aperture runs obliquely 
relative to the contact face in the direction of the aperture and at an 
angle, diverging preferably from the insert side, of 1.degree. to 
10.degree., preferably 2.degree. to 5.degree.. 
The enclosed, gap-shaped aperture preferably is formed by spark-erosive 
cutting with a wire-electrode arrangement. In order to facilitate 
production, the aperture ends can include, to this end, a cross section 
which is widened relative to the gap cross section and can be produced by 
a boring operation.

DETAILED DESCRIPTION 
The cartridges 10 represented in the drawing are intended to receive 
indexable throwaway inserts made from hard metal, a ceramic cutting 
material or other cutting materials and are predominantly used for turning 
jobs. To this end, the cartridges 10 are fastened by a tightening screw 11 
(FIG. 6b) to a tool carrier 12 preferably configured as a boring bar. 
The cartridges essentially comprise a holder shank 14 and a holder head 16, 
which is formed with the front side onto the holder shank 14 and protrudes 
in a step shape outwardly beyond said holder shank. The holder shank 14 
includes a contact face 20, which is obliquely passed through by an 
elongate hole 18 for the reception of the tightening screw 11 and which 
bears against an axial clamping face 22 of the tool carrier 12. The holder 
head 16 is provided with a recess 24 which is open at the margin and, in 
which an indexable throwaway insert 26 is disposed such that an active 
tool nose 28 thereof protrudes toward the outer face 30 which faces away 
from the contact face 20. The distance measure f between the clamping face 
22 of the tool carrier 12 and the tool nose 28 can be set, within certain 
limits, by the adjusting device explained in greater detail below. 
The adjusting device essentially comprises a gap-shaped aperture 32, which 
passes parallel to the contact face 20 through the holder head 16 and 
which is disposed in the free region between the recess 24, the contact 
face 20 and the holder shank 14 and includes an arc-shaped channel which 
is open toward the holder shank 14 and is limited by the enclosed aperture 
ends 34, 36 widened in their cross-sectional dimension. The aperture ends 
34, 36 are disposed in a plane perpendicular to the contact face 20 and 
limit, with the contact face 20 and the outer face 30, respective 
thin-walled material bridges 38, 40. The holder head 16, in the region of 
the two material bridges 38, 40, is elastically bendable relative to the 
holder shank 14 and perpendicularly to the contact face 20 under the 
influence of a control member 42. 
As can be seen, in particular, from FIG. 1d, the aperture includes, 
respectively, a gap segment 46 located on the outer face side and lying 
parallel to the contact face 20 and a gap segment 48 located on the 
contact face side, which are interconnected by a bent cross or transverse 
section 50 remote from the shank. While the gap segment 48 located on the 
contact face side is directly limited by the aperture end 34 lying close 
to the contact face, the gap segment 46 located on the outer face side is 
connected, via an oblique segment 52 running obliquely to the shank side 
and in the direction of the outer face 30, to the aperture end 36 lying 
close to the outer face. In this way, a shank-fixed extension arm 54 is 
formed, which, with its outer flanks, defines the gap segments 46, 48, 50, 
52 on the inner side. 
In the illustrative embodiment shown in FIGS. 1a to f, the control member 
42 is formed as a setting screw, which is guided into an internal thread 
44 of the holder head 16 perpendicularly to the contact face 20 and with 
its flattened end face 56 extends through the gap segment 46 located on 
the outer side and can be pressed against the shank-fixed extension arm 
54. The setting screw 42 is accessible through the outer face 30 of the 
holder head 16. It includes a head 58 having a hexagonal socket 60, which 
head has a scale graduation 62 in the annular region thereof surrounding 
the hexagonal socket 60. Instead of a zero mark, the holder head 16 
includes, in the region of its outer face 20, an orientation edge 64 
extending radially to the internal thread 56. By tightening of the setting 
screw 42 against the shank-fixed extension arm 54, the holder head 16, in 
the region of the material bridges 38, 40, is bent elastically outward 
relative to the holder shank 14, with the distance measure f being 
adjusted and its angular orientation being maintained. Given suitable 
calibration, the distance alteration can be read directly from the scale 
62. 
In the illustrative embodiment shown in FIG. 2, the holder head 16 includes 
an internal thread 66 which is aligned parallel to the contact face 20 and 
in which a setting screw, accessible through the front side, is guided as 
a control member 42. There, the setting screw 42 bears with its conical 
tip part 68 against an oblique part of the curved transverse segment 50 
and when tightened, results in a bending of the holder head 16 relative to 
the holder shank 14 in the region of the material bridges 38, 40 and hence 
to an adjustment of the distance measure f. 
In the illustrative embodiments according to FIGS. 3 and 4, the control 
members 42 are disposed, in the form of a radial and axial setting screw, 
in the tool carrier 12. In the case of FIG. 3, the setting screw bears 
with its flattened tip against the contact face 20 in the region of the 
holder head 16 and, in the case of FIG. 4, with an outer cone 68 against a 
wedge face 70 in the rearward, frontal region of the holder head 16. By 
tightening the setting screws 42 in question, the holder head 16, in the 
region of the material bridges 38, 40, is bent elastically outward 
relative to the holder shank 14, the distance measure f being altered. 
In the illustrative embodiment according to FIG. 5, instead of the setting 
screw there is provided, as a control member 42, a control body guided in 
a slideway of the tool carrier 12, which control body can be actuated by 
means of a setting rod 70 having a wedge bevel 74, which setting rod is 
guided in the tool carrier 12 and is displaceable centrally, by means of 
the machine tool, in the direction of the double arrow 72. 
In the illustrative embodiments shown in FIGS. 6a to c and 7a to c, the 
control members 42 are configured as setting screws which pass through the 
holder head 16 and are supportable with their flattened end face 56 
against the clamping face 22 of the tool carrier 12 and which extend 
through the internal thread of a threaded bushing 82 disposed in a recess 
80 of the holder head 16. The threaded bushing 82 is inserted through the 
contact face 20 into the recess 80 and is supported with its front edge 84 
pointing toward the clamping face 22 against an annular shoulder 84 within 
the holder head, on the outer side of the gap segment 46 located on the 
outer face side. For the rotational securement of the threaded bushing 82, 
the threaded bushing 82, in the illustrative embodiment according to FIGS. 
6a to c, includes a hexagonal segment 86, which is engaged within a 
complementary hexagonal socket 88 of the recess 80. A cylindrical 
centering lug 90, which is engaged within a cylindrical segment 92 of the 
recess 80, in this case ensures a centering of the threaded bushing 82 in 
the holder head 16. In the illustrative embodiment according to FIGS. 7a 
to c, the threaded bushing 82 includes an outer surface which is 
cylindrical over the entire height and which, in the recess 82, is secured 
against twisting on the holder head 16 with the aid of a securing screw 94 
which intersects the outer surface. By tightening the setting screw 42 
against the clamping face 22 of the tool holder, the threaded bushing 82 
is simultaneously supported against the inner shoulder 88, and the holder 
head 16, in the region of the material bridges 38, 40, and is bent 
elastically outward, with the distance measure f being adjusted. 
By way of a summary, the following can be stated: the invention relates to 
a tool holder for indexable throwaway inserts, which is used, above all, 
for turning jobs. The tool holder essentially comprises a holder shank 14 
and a holder head 16 connected thereto in one piece. The holder shank can 
be fastened to an axis-parallel clamping face of a tool carrier 12 with a 
contact face 20 being obliquely passed through by a tightening screw. The 
holding head 16 includes a recess 24 open at the margin for the reception 
of the indexable throwaway insert 26, which insert protrudes on one side 
with an active tool nose 28 beyond the outer face 30 that is facing away 
from the contact face 20. In order to enable an adjustment of the distance 
f between a clamping face 22 and the tool nose 28, the holding head 16 is 
provided with a gap-shaped aperture in the free region between the recess 
24, the contact face 20 and the holder shank 15, which aperture exhibits 
an arc-shaped cross-sectional contour that is open toward the holder shank 
14. The holder head is elastically bendable relative to the holder shank 
14 under the influence of a control member 42.