FIELD OF INVENTION:
The present invention relates to an improved tool holding device for machining of
areas close to the walls of high pressure casing on vertical boring machines avoiding
collision of the machine RAM with the body of casing. More particularly, the invention
relates to the indigenous development of a special tool holding device to provide clearance
between Machine RAM (Shown in Fig.2) and to machine job without any vibration for
details near the walls of High Pressure Outer Casing (HPOC) on a vertical boring machine,
resulting in distinct advantages over conventional clamping procedure which may result in
collision if proper care is not taken and also takes more machining time and low quality of
products machined.
The said tool holding device has been designed to be used in all vertical boring
machine universally.
BACKGROUND OF THE INVENTION:
I-ring groove of High Pressure Outer Casing (HPOC) are regularly machined on
vertical boring machines. In HPOC machining of I-RING groove detail (shown in fig.l) is
very critical operation due to its precise dimensions and machining constraints due to use
of long tool overhang to avoid machine RAM collision with casing body. In order to
machine the I-RING groove detail every time a long L- shaped tool is required to be
clamped in such a way that it will provide clearance between RAM and job. But it

generates vibration while machining due to long overhang. If we reduce overhang of tool
to reduce vibrations, it causes collision while positioning, for machining. There is no
provision on the machine to clamp the long L- shaped tool rigidly which can avoid
vibration and also avoids collision with RAM. Thus it becomes very difficult to machine the
I-RING groove detail as well as similar profile which need long tool overhang and good
surface finish. This necessitates a designing of a improved tool holding device for the
machine which is compatible with clamping arrangement on the RAM of the machine.
OBJECTS OF THE INVENTION:
Therefore, it is an object of the invention to propose an improved tool holding
device for machining of areas close to the walls of high pressure casing on vertical boring
machines avoiding collision of the machine RAM with the body of casing which is capable
of machining I-ring groove without vibration and without having a collision of machine
RAM with casing body.
Another object of the invention is to propose an improved tool holding device for
machining of areas close to the walls of high pressure casing on vertical boring machines
avoiding collision of the machine RAM with the body of casing which is able to
accommodate different type of square shank tools resulting reduced machining cost.
A further object of the invention is to propose an improved tool holding device for
machining of areas close to the walls of high pressure casing on vertical boring machines
avoiding collision of the machine RAM with the body of casing which is capable of
achieving good surface finish and accurate profiles.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Fig. 1 : Shows sectional figure of HPOC showing I-ring groove detail near the wall.
Fig. 2 : Shows the present methodology with straight holder and L-shaped grooving
tool.
Fig.3 : Shows the developed methodology with new improved tool holding device
and straight cutting tool.
Fig.4 : Shows enlarged view of developed holder.
Fig.5 : Shows developed holding device with slot.
Fig.6 : Shows a line diagram of developed holder.
Fig.7 : Shows the outer casing in HP turbine.
Fig.8 : Shows collision between machine RAM & walls with existing alternative
method.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION:
The innermost part of the HP turbine is HP rotor. Then it is covered by HP inner
casing. HP outer casing is the outermost part of the HP turbine as shown in Fig.7. HP
turbine is connected to IP turbine.
I-RING groove detail is located at a depth of around 2000mm from the top face of
the work piece. The run out on the groove diameter has to be maintained. The run out
value of 0.02 mm needs to be achieved having close tolerances of 0.05mm with surface
finish of 1.6 microns Ra.

As per Fig. 2 in the existing methodology an L shaped tool is clamped to machine
the detail in HP Outer Casing. The tool is clamped in a standard straight cassette provided
by the machine OEM (Original Equipment Manufacturer). The width D of the tool cannot
be more than 6mm so as to machine the detail in the HPOC. Due to this slender thickness
the strength of the tool is reduced a lot. And since this being L rigidity is compromised.
In the prior Art the L shaped grooving tool (Fig.2) is used having long overhang to
avoid collision between RAM and internal diameter of the job. Due to the extra overhang
of the tool, while machining I-RING detail it gives chattering and thereafter it becomes
very difficult to machine and also dimensions get deviated. The dimensions of I- RING are
very precise which houses the component used to seal the steam at very high pressure
which makes the machining of this detail very critical.
Cuts at very low feed and rpm are taken to minimize the chattering and to get
desired surface finish.
To prevent the vibration a face grooving tool can be used in a straight vertical slot
holder. In this case tool clamping is more rigid that can provide good surface finish. This
machining strategy causes collision between RAM and work piece as shown in fig.8. To
avoid this problem we have to provide required clearance between RAM and work piece
by using a different holding device.
In the present developed method the tool holding device has been designed in such
a way that it can provide sufficient clearance between RAM and work piece. Fig.5 shows

developed L shaped holding device (cassette) having sufficient rigidity. The dimensions of
holding device are designed in such a way that it can be used in all vertical borer
machines universally for machining of these types of components. It provides flexibility of
tool having any shank cross section and tool width as per requirement of work piece.
In the new developed holder (show in Fig. 4) instead of using a straight holder
improved tool holding device is used. This tool holder being a part of the cassette is very
rigid as it is an integrated single piece. In this holder a 45mm X 36mm groove is cut to
accommodate tools of different shank sizes like 40 X 40 mm, 40 X 32 mm, 32 X 32 mm.
The tool is hold rigidly by 4 M 10 screws. And since the overhang is minimized the tools
works at optimum parameters. The developed holder is universal in nature which means
that it can work on any GNC vertical borer.
Also the length of the tool and cassette is adjustable which gives the flexibility of
varying tool lengths for different job. Also the cassette can be changed easily for any tool
change. No need of changing complete holder for any tool change. (Refer Fig 4 for
enlarged view)
The improved tool holding device (1) is shown in Fig.4 and 5. The holding device
(1) is a L-shaped integral structure having a slot (2) in the front portion of the device for
accommodating the tool (4) (as shown in Fig. 4) which is clamped inside the slot (2) of
holding device (1) by means of screws (3). Various sizes of square shank tools are

accommodated in the slot (2) and are clamped by the screws. The L-shaped holder is
integrally machined and is made of mild steel, carburized hardened and grinding finished
and having a plurality of threaded holes (3) for clamping the tool (4) and a slot (2) for
accommodating a cutting tool. The slot has 45mm width and 35mm depth.
In the prior Art the holding device (6) was straight and the tool (5) was of L-
shaped, as shown in Fig.2. In the present invention the holder (1) (Fig. 4 and 5) is of L-
shaped and the tool (4) is a straight face grooving tool.
The component to be manufactured is High Pressure Outer Casing (HPOC) as
shown in Fig.l. The component has I-RING groove detail which houses the component
used to seal the steam at very high pressure which makes the machining of this detail
very critical. (Refer Figure 1).



The following are the benefits accrued after changing the process of machining and the
use of an improved tool.
1. Productivity: Total machining time of HP Outer Casing on CNC vertical borers is
reduced.

2. Quality: By using above clamping device required drawing accuracies and surface
finish are achieved that's why quality of machined component is improved.
3. Financial Benefit: As cycle time is reduced critical CNC machine availability is
increased to take up more nos. of components.
4. Power Saving: Overall Productivity & Utilization of machine is increased hence
power consumption was reduced.
5. Health and working condition: As clamping and unclamping is reduced, so machine
operators will face less fatigue.
6. Financial Saving: Time saved in machining of HP Outer Casing = 4 hours
Machining Cost = Rs. 13320 per hour.
Total saving = 13320*4 = Rs. 53280
Average No. HPOC machined per year = 10
Total saving per year =10*53280= Rs. 5.32 Lacs
7. Tool Safety: Less tool breakages as working length is optimum which does not put
any additional stress on the tool.
8. Personal Safety: Frequent handling of tool is reduced. Tool change has become
simplified since now there is no need of changing the entire holder. There is no chance of
collision also.

WE CLAIM:
1. An improved tool holding device for machining of areas close to the walls of high
pressure casing on vertical boring machines avoiding collision of the machine RAM with
the body of casing, the said device (1) comprising;
a L-shaped integral structure having a slot (2) in front of the structure for
accommodating a straight shaped grooving tool for machining I-ring grooves of high
pressure outer casing and having a plurality of threaded holes on the side of slot (2) for
clamping a tool (4) accommodated in the slot (2) wherein the slot accommodates square
shank tools of various sizes when rigid clamping of the tool allows employing higher
machining parameters of speed and feed resulting reduced machining time and superior
surface finish wherein the collision of machine RAM with the body of casing is totally
avoided.
2. An improved tool holding device as claimed in claim 1, wherein the said device is
made of mild steel carburized and hardened.
3. An improved tool holding device as claimed in claim 1, wherein the slot of the
holder has 45mm width and 36 mm depth.