Note: Descriptions are shown in the official language in which they were submitted.
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The invention concerns a boring tool with a
radially adjustable boring bit.
One such known boring tool (DE-OS 2 040 020),
which is intended in particular for precision boring, has
radial adjustment of the boring bit by axial movement of a
pushing rod mounted in the machine-tool spindle. The front
end of the pushing rod forms an adjusting body with a slightly
inclined wedge face. On this wedge face rests a bracket
connected to a springy, suitably supported boring bar, which
mounts the boring bit.
A radial adjustment outwardly of the boring bit
may be necessary in order to keep constant the diameter of a
bore machined with a particular bit. For instance after a
machining operation the cutting edge of the boring bit may
have undergone a certain amount of wear and during the next
machining operation, the bore diameter would be smaller than
the specified size.
A radial adjustment inwardly of the boring bit
also can be used to remove the bit from a machined surface
when withdrawing it after a machining operation. This
avoids any marking by the bit on the surface during with-
drawal.
Finally, radial adjustment within narrow limits
can also be used to produce successive bores or bore sections
with slightly differing diameters. For example successive
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bore sections with the same rated diameter but different
tolerances.
For a bit to be useful all parts of the bit must
assume a position of maximum stability after they have been
adjusted. Every axial position of the pushing rod must be
co-ordinated, clearly defined and have high repetition
accuracy for a given, radial adjustment of the boring bar.
In the case of the above known boring tool the
bracket connected to the boring bar is supported only in one
direction and only on one wedge face. In this connection
the spring action of torsion rods mounted on the boring bar
furnish the contact force on the wedge face. In order to
avoid any settling during contact on the wedge face, i.e. to
ensure that the adjustment of the boring bar changes as
little as possible durlng the machining process, it is
necessary that the initial stressing force with which the
bracket is pressed against the wedge face be made as high as
possible by a suitable selection of the torsion rods. This
requires very accurate guidance, as far as possible without
play, of the adjusting body in its guide bore.
In the case of the known boring tool there require-
ments can only be attained with great difficulty, because
the guiding bore is formed by the spindle bore itself. If
this bore is to be produced with sufficiently high accuracy,
and if the adjusting body is to be guided with sufficiently
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close fit and high accuracy, the known boring tool can be
used only with machine-tool spindles specially designed for
this purpose.
The purpose of the invention is to design a boring
tool of the type outlined that can be used with conventional
rather than specially designed machine-tool spindles and
nevertheless permit a very accurate adjustment of the boring
bit with high repetition accuracy.
Accordingly, the invention is a boring tool with a
radially adjustable boring bit, comprising: a boring bar,
supporting the boring bit, connected via torsion rods
arranged transversely to its longitudinal axis to a supporting
ring which can be mounted via a housing cylinder on a spindle
flange of a rotatable machine-tool spindle; the boring bar
being connected at its end facing the machine-tool spindle
rigidly to a bracket; the bracket resting on a slightly
inclined wedge face of an adjusting body guided in a guide
hole, movable axially by means of a pushing rod for a radial
adjustment of the boring bit; a guide hole located at least
partially inside the housing cylinder and centred in the
latter; a second wedge face formed on the adjusting body,
opposite the wedge face and parallel to the latter; and the
bracket being guided between the two wedge faces with form-
closed contact.
The form-closed, and therefore practically play-
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free and deformation-free, support of the bracket connected
to the boring bar acts along the direct path of the force
flow on the housing cylinder without requiring any guidance
in the spindle bore. Thus no demands are made regarding the
accuracy of the existing spindle bore. Consequently the
boring tool according to the invention can be used with
different machine-tool spindles without reducing the accuracy
of the machining.
It was found to be of particular advantage to form
the guide bore on a guiding and centering sleeve which is
centred inside the housing cylinder and which can protrude
with a cylindrical shoulder into a spindle bore of the
machine-tool spindle, where an additional, but no essential,
centering can be made. Of importance is the centering of
the housing cylinder in relation to the spindle flange,
which can be made on a short centering cylinder usually
present on machine-tool spindles of this type.
The invention is illustrated, by way of example,
in the drawings in which:
Figure 1 is a boring tool in longitudinal section,
mounted on a machine-tool spindle,
Figure 2 is a view in direction of the arrow II-II
in Figure 1, in which the boring bar is omitted, and
Figure 3 is a section along the line III-III in
Figure 1.
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A boring bar 1, which mounts a boring bit 2, is
connected to a supporting ring 4. The ring 4 is connected
to a housing cylinder 5 via two torsion rods 3 mounted
transversely to the longitudinal axis of the boring bar 1.
The housing cylinder 5 is screwed to a flange ring 6 which,
with the insertion of a flange 7, is screwed to a spindle
flange 8 of a machine-tool spindle 9 having a spindle bore
10 .
The boring bar 1 is connected rigidly to a bracket
11 at its end facing the machine-tool spindle, whereby the
boring bar 1 and/or bracket 11 can be screwed together with
a plate 3' located between the two torsion rods 3 and
whereby the plate 3' can form a single piece with the
torsion rods 3 and supporting ring 4. For this purpose
approximately semi~circular slots 12 can be milled in a
disc-shaped blank.
Near its free end the bracket 11 carries on
opposing sides two sliding bodies 13. These bodies 13
allows the bracket 11 to rest on a first wedge face 14
located on the same side as the drilling bit 2, and on a
second wedge face 15 which faces the wedge face 14. Face
15 is parallel to face 14. The two wedge faces 14, 15 are
formed on a forked adjusting body 16 and are inclined at a
slight angle of approximately 1 to 2, relative to the
longitudinal axis of the spindle.
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With its cylindrical outside face the adjusting
body is guided in a guide bore 17 in a guiding and centering
sleeve 18, which is centered in an internal bore 19 of the
housing cylinder 5. The guiding and centering sleeve 18 is
connected as one single piece to the flange 7 and a cylindrical
shoulder 20. Shoulder 20 protrudes into the spindle bore 10
where it can also be centered if the spindle bore is machined
with sufficient accuracy.
A fitting key 21 attached to the adjusting body 16
is guided in a keyway 22 of the cylindrical shoulder 20 and
prevents any rotation of the adjusting body 16, relative to
the guiding and centering sleeve 18.
A pushing rod 23 mounted in the spindle bore 10 is
connected to the adjusting body 16. The bracket 11 is
supported on the wedge faces 14 and 15 in a zone located
outside the spindle bore 10 and largely inside the housing
cylinder 5 and the sleeve 18 connected to it.
By an axial adjustment of the pushing rod 23
releasably attached to the adjusting body 16, the bracket 11
is shifted radially by the slightly inclined wedge faces 14
and 15 in such a way that the free end of the boring bar 1
which carries the boring bit 2 is displaced radially in the
opposite direction. The torsion rods 3 provide the support
for this movement.
- The boring tool, as a unit, can be unscrewed from
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the spindle flange 8, whereby the adjusting body 16 is
detached likewise from the pushing rod 23.
In the practical example shown in the drawing, the
boring bar 1 is connected exchangably to the plate 3', which
in turn is machined in one piece with the bracket 11.
