FIELD OF INVENTION:
The invention relates to an intermediate device for rigidly holding the long
heavy weight boring heads on heavy CNC Horizontal boring machine (HB) for
accurate machining of narrow small diameter deep diffuser bores of turbine
casing and the method for the same.
BACKGROUND OF THE INVENTION:
Referring to Figure 1, for deep bores machining on any turbine casing, the
CNC Horizontal Boring Machine (HBM) (Pos.No.l) is used. HBM is having milling
spindle (10) for rotating the cutter (tool) and boring spindle (9) for holding the
long boring head and moves the cutter (tool) front and back. The holding means
is called the pull stud (6) & collet (5) locking mechanism. This mechanism is
operated by hydraulic power within its holding capacity. Job is placed on the
machine bed. Boring head (4) will enter into the job for boring the deep holes.
Long boring head is essential for accurate machining the narrow small diameter
bores. The boring spindle (9) has to enter into the turbine casing for deep
diffuser bores machining. In some cases, the bore diameters are smaller than the
spindle diameter and hence the spindle cannot enter into the casing. At this
situation there must need a heavy duty long boring heads for accurate machining
the diffuser bores. In these bores of turbine casing, nozzles are shrink fitted and
hence no deviation is allowed in the dimensions of the bores.
Referring to figure 1. Presently long boring head (4) is used for machining
deep diffuser bores. The long boring head is held in the machine's boring
spindle(9) by pull stud (6) and collet (5) locking mechanism. Due to the weight
and overhang of the heavy weight long boring head (4), during machining,

heavy vibrations and chattering are generated. This results in frequent failure of
tool locking and unlocking pull stud and collet mechanism of the machine and
damaging the HBM (1) spindle bearings.
OBJECTS OF THE INVENTION:
Therefore, it is an object of the invention to propose an intermediate
device for rigidly holding the long heavy weight boring heads on heavy CNC
Horizontal boring machine (HB) which can eliminate the possibility of frequent
damage of the locking mechanism and thus eliminate the high breakdown cost of
CNC HB machine by 100%.
Another object of the invention is to propose an intermediate device for
rigidly holding the long heavy weight boring heads on heavy CNC Horizontal
boring machine (HB) which is capable of improving the productivity by 100%
utilisation of the CNC HB machine.
A further object of the invention is to propose an intermediate device for
rigidly holding the long heavy weight boring heads on heavy CNC Horizontal
boring machine (HB) which is able to impart rigidity and stiffness to the long
heavy weight boring head for machining deep diffuser bores and thus eliminate
heavy vibration and chattering during machining.
A still another object of the invention is to propose an intermediate device
for rigidly holding the long heavy weight boring heads on heavy CNC Horizontal
boring machine (HB) which is capable of attaining the quality of the diffuser
bores required in the design.

SUMMARY OF THE INVENTION:
To avoid damage to the pull stud and collet locking mechanism and to
rigidly holding of long heavy weight boring head on CNC horizontal boring
machine's ram (2) (Fig.3), an intermediate device (12) (Fig.2) is invented which
replaces the pull stud and collet locking mechanism. The device consist of a
recess (13) (Fig.2) for accurate location on spigot (7) (Fig.3) of the machine's
milling spindle and is having 6-numbers of through holes (15) (Fig.2) on a pitch
circle diameter (PCD) for placing the locking bolts for rigidly fixing it on machine
ram. At front side of the device having pin (18) (Fig.2) for accurate locating the
long boring head to maintain inline axis of machine spindle and boring head.
Around the pin, having 4-numbers of threaded holes(16) (Fig.2) on PCD of the
invented device for fixing the long boring head by bolts.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS:
Fig. 1 : Shows Pull stud and collet locking mechanism for holding heavy weight
long boring heads according to prior art.
Fig.2 : Shows an invented intermediate device according to the invention.
Fig.3 : Shows an invented intermediate device for rigid holding heavy weight
boring heads according to the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION:
Fig.2 shows the newly invented intermediate device (12) is used for rigid
holding the long heavy weight boring heads on horizontal boring machine ram

(2) (Fig.3). The device consist of a recess (13) for accurate location on spigot (7)
(Fig.3) of the machine's milling spindle (10) (Fig.3) and having 6-numbers of
through holes (15) on a pitch circle diameter (PCD) for placing the locking bolts
for rigidly fixing it on machine ram (2). At front side of the device (12) having pin
(18) for accurately locating the long boring head to maintain inline axis of
machine spindle (9) and boring head (4). Around the pin (18), having 4-numbers
of threaded holes (16) on PCD of the invented device (12) for fixing the long
boring head (4) by bolts.
Fig.3 shows the newly invented intermediate device (12) is first held on
the CNC HB machine's (1) milling spindle face of the ram (2) by accurately
locating on the spigot (7) of the milling spindle. The device is rigidly fixed by 6-
numbers of bolts in the existing holes (15) (Fig.2) on the machine ram (2).
The long boring head (4) having a recess is located on the pin (18)
integrated with the intermediate device (12) and rigidly fixed by 4-numbers of
bolts (16) (Fig.2). These additional added (6+4) bolts and its increased con tact
area increases the stiffness and rigidly to the long boring head.
Through this invention, pull stud and collet locking mechanism was
completely avoided for holding heavy weight long boring heads. Hence the
machine boring spindle is placed at its zero position (9) inside the ram (2).
DISADVANTAGES OF THE PRIOR ART:
> Due to heavy weight and overhang of the long boring head, the pull stud
and collet mechanism of the machine gets damaged frequently.
> For heavy weight long boring heads, the holding mechanism is less rigid.
> Generates heavy vibrations and chattering during machining.
> Required limits of accuracy on the finish machined bores are not achieved.
> Frequent breakdown of the machine during machining.

ADVANTAGES OF THE PRESENT INVENTION:
> The invention increases rigidity and stiffness of the long heavy weight
boring head for machining deep diffuser bores and eliminates the draw
backs of the prior art.
> The invention improves the quality of diffuser bores within designed limits
and saves a lot of time for rework as in prior-art and to increases the
productivity by using multi point cutter.
> The invented intermediate device is useful at all CNC HB machines for
machining deep bores eliminating the unsafe working condition.

WE CLAIM
1. An intermediate device (12) for rigidly holding the long heavy weight
boring heads on heavy CNC Horizontal boring machine, the said device
comprising and characterized in that;
a recess (13) having a diameter matching the spigot (7) of the milling
spindle (10);
a plurality of holes (15) for fixing the said device (12) on the ram with
bolts;
a locating pin (18) having diameter suiting to the recess bore of a boring
head (4) the said locating pin disposed on the device (12) for accurately locating
the boring head in the same axis of the machine spindle (10) wherein the boring
head (4) is fixed rigidly on the device (12) by bolts on a plurality of threaded
holes (16) disposed on the device (12) around the locating pin (18).
2. The intermediate device as claimed in claim 1, wherein the holes (15) for
fixing the device (12) are six numbers of pitch circle diameter holes of diameter
28mm.
3. An intermediate device as claimed in claim 1, wherein the threaded holes
(16) for fixing the boring head with the device are four numbers of pitch circle
diameter threaded holes of diameter M20 size.
4. An intermediate device as claimed in claim 1, wherein the recess diameter
(13) of the device (12) sitting on the spigot (7) of a machine spindle is 275-285
mm.

5. An intermediate device as claimed in claim 1, wherein the diameter of the
locating pin (18) 55-65 mm.
6. A method for accurate machining of narrow small diameter deep diffuser
bores of turbine casing by the device claimed in claim 1, the said method
comprising;
making an intermediate device (12) with an integrated locating diameter
having a recess (13) of 275-285 mm diameter with six PCD holes disposed on it;
assembling the said device (12) on the spigot of the machine spindle (10)
of ram (2) with bolts;
making a long heavy boring head (4) with a recess matching the diameter
of the locating pin;
wherein the long boring head is assembled with the intermediate device
fixing the recess of the said head (4) on the locating diameter (18) of the
intermediate device (12) for accurate machining of deep diffuser bores of
turbine.

ABSTRACT

An intermediate device (12) consisting of a recess (13) for accurate
location on spigot (7) of a CNC horizontal boring machine's milling spindle is
fixed to the machine ram (2) by six bolts on a pitch circle diameter holes (15). A
long boring head (4) having a recess is fixed rigidly to the locating pin (18) of
the intermediate device (12) by four bolts in a threaded holes (16) making the
axis of the boring the head (4) in alignment with the axis of the machine spindle.