FIELD OF INVENTION
The present invention relates to the development of a tooling arrangement for
machining of taper pin holes on joint plane of HP turbine in assembled condition which
needs proper approach due to criticality of machining space More particularly, the
invention relates to the development of tooling system for machining of taper pin holes
on HP turbine in assembled position, where the machining operation involved is drilling
and reaming.
BACKGROUND OF THE INVENTION
A steam turbine is a device that extracts thermal energy from pressurized steam and
uses it to do mechanical work on a rotating output shaft. Depending upon the steam
inlet pressure, turbines are distinguished into three types viz, High Pressure Turbine
(HPT), Low Pressure Turbine (LPT), and any turbine in between HPT and LPT is an
Intermediate Pressure Turbine (IPT). All turbines contain three necessary and essential
components viz. a rotor, which serves as the center of the rotation motion of turbine,
secondly, blades to guide the steam from inlet to the outlet of the turbine and deliver
the necessary rotation motion to the rotor thereby converting heat energy and pressure
of the incoming steam into mechanical energy (rotation) and lastly, a casing (inner and
outer)(refer fig. 1) which serves to cover all the assemblies and keep the steam intact
in the system. The outer casing of a HP Turbine comprises of two halves, i.e., inlet end
and exhaust end and to locate and align these two halves of the outer casing perfectly
with respect to each other during assembly, taper pin is used in a taper hole at the joint
plane of the two halves of the outer casing. This taper hole is divided into the inlet as
well as exhaust end of the outer casing. These pin holes are tapered and are required
to machine with high accuracy.

In the prior arts, while machining these taper pin holes, there was high risk of
damaging the taper holes or the subsurface of the hole or both.
During drilling (for simple hole) or reaming (for widening the hole to give taper shape in
case of blind hole), there are chances that the chips will accumulate inside the hole and
due to high heat of machining as well as friction, the chips will melt and stick to the
tool, thereby restricting its cutting motion. When this happens, the tool gets constrained
in its circular motion while the spindle remains in motion, which results into unlocking of
drill/reamer shank and the sleeve. This results into most crucial drawback of the prior
art where the drill/reamer remains inside the hole after getting unlocked with sleeve.
Since, short drills cannot be used to attain the full depth of holes, the whole outer
casing assembly has be disassembled for taking out the drill/reamer and assemble back
to restart the drilling/reaming process. This takes sometime between 250-300 man-
hours and equivalent time loss in engagement of the EOT Crane, which directly affect
delivery schedule of the turbine accompanied with other related disadvantages.
Another constraint for drilling is the approach of drills as the long drills fouls with the
outer body of the turbine and short drills cannot drill to the full depth. The job
requirement is that the hole should align perfectly. As the component is of high value,
any misalignment while machining could result in rejection of job and delay in project.
Therefore an alternate arrangement of tools is to be developed for drilling operation.
OBJECTIVE OF THE INVENTION
1. The object of the present invention is to develop a tooling system for
machining of tapered pin holes on HP turbine with proper approach to complete the
machining accurately and timely.

2. Another object of the invention is to develop a tooling system for machining of
tapered pin holes on HP turbine to avoid the drill/reamer getting unlocked and
remaining inside the hole thus avoiding the dismantling of whole outer casing again.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
1. Supercritical HP Turbine assembly(Fig. 1)
2. Tooling arrangement for drilling(Fig. 2)
3. Tooling Arrangement for reaming (Fig. 3)
SUMMARY OF THE INVENTION
The invention relates to the machining of taper pin holes on joint plane of supercritical
HP turbine in assembled condition which needed proper approach due to non
availability of proper machining space.
The tooling components for drilling as well as reaming arrangement are as follows:
1. Sleeve (1)
2. Extension sleeve (2)
3. Drills bit (3)
4. Locking arrangement (sleeve and spindle) (7)
5. Locking arrangement (bit and sleeve) (8)
6. Reamer Tool (6)

In the present invention (fig. 2), the sleeve (1) through its outer diameter (BT50) fits
into the taper hole of the Milling head spindle through Allen bolt. The long extension
sleeve (02) in which one end having MT5 (BT 50 taper) taper will get locked with sleeve
(01) and the locking pin (05) will be provided to ensure positive locking of sleeve (1)
with long sleeve (2). The long extension sleeve (2) will get locked at its other end to
the drill bit/reamer (3, 6) through twin locking arrangement again. The drill bit's
tapered shank (through it outer dia) and long (sleeve through its inner dia) will fit
together through the taper fitting process. The locking pin (04) is also provided to
ensure that when the drill bit is taken out of the machined hole, the drill bit does not
remain inside the machined hole.
Since after drilling the hole, the hole is to be tapered through reaming process, hence
the same methodology has to be implemented for reaming process by the reamer (6).
(fig. 3).
Benefits Incurred
1. Productivity: This method ensures drilling and reaming in HP outer casing with high
accuracy which reduced cycle time. This method avoids risk of damage to the hole
while using long drills.
2. Quality: By carrying out the drilling operation with the developed arrangement, high
accuracy on the required size hole is achieved. The chances of any misalignment are
avoided and good finishing on the drill hole is attained.
3. Utility of the design: The method can be used on for all deep drilling operations on
horizontal bore machines, where limited approach is available.

4. Safety: The system guides and supports the drills so that the operator does not to
manually align the drill every time it retracts to clear the chips. This makes the process
safer and it also avoids any possibility of damage to the drill due to vibration which
could otherwise seriously injure the operator and could damage the workpiece.
5. Time Saving: Conventionally the operator use drills of various lengths and align the
drill every time. This consumes lot of effective time and increases the time cycle for job
completion. With the implementation of the tool setup, operator can machine the job in
single pass which saves a lot of machining time.
6. Technological Improvement: The technological improvement by the use of
developed tooling arrangement can be applied in all such areas where limited approach
/accessibility is available.

WE CLAIM:
1. Tooling system for machining of taper pin holes on HP turbine in assembled position
comprising:
a sleeve (01) having a taper of MT 5 at inner diameter at one end and a taper BT 50 at
outer diameter on the other end which is to be fitted in the milling head spindle of the
machine having the same taper BT50;
an extension sleeve (02) having MT 5 taper at outer diameter at the first end and MT4
taper at the 2nd end, the 1st end being fitted into the MT 5 taper at inner diameter of
sleeve (01) and locked by the locking pin (5) at. position (7) shown in Fig 2/ fig 3;
a drilling bit /reamer (3, 6) having shank with taper MT 4 being fitted into the 2nd end
of extension sleeve (2) having same taper MT4 at inner diameter and being locked by
the locking pin (4) at position (8);
wherein the locking pin (4) are taken out whenever there is any shift from type of
operation i.e. from drilling to reaming or vice versa.
2. A method for drilling or reaming by the arrangement as claimed in claim 1
comprising:
- inserting one end of the sleeve (1) having a taper BT 50 at outer diameter into the
machine spindle of the milling head having BT 50 taper,
- inserting the 1st end of the extension sleeve (02) having MT5 taper to the other end of
the sleeve (01) having the same BT 5 taper in the inner diameter;
- locking the components (1) and (2) by a locking pin (5) at position (7);

- inserting the drilling bit (3) by the shank portion having MT 4 taper into the second
end of the extension sleeve (02) having the same MT 4 taper in the inner diameter;
Locking components (2) and (3) by the locking pin (4) by the locking arrangement at
position (8);
Performing the drilling operation in the job;
Removing the locking pin (4) after the drilling operation is completed;
Loading the reamer (6) and repeating the process for performing reaming operation.