FIELD OF INVENTION
The present invention relates to development of a guiding and vibration dampening
fixture for long drills to be used in all types of deep drilling operations in turbine
components. More particularly, the invention relates to a guiding and vibration
dampening fixture used in all types of deep drilling operations in different turbine
components.
BACKGROUND OF INVENTION
An interceptor valve and Control valve (IV/CV) is used in IP steam turbine to control the
steam input to the IP turbine according to the load requirement. The valve IV/CV
consists of many parts; one such part is a hollow cylindrical shaped 'diffuser' (Refer Fig
1).
The diffuser has stellite material deposition at the both ends. The diffuser connects the
reheat steam pipe form boiler to the IP turbine.
As per the design, a multi size through deephole is to be drilled with dimensions
dia.25X900mm on one side and dia. 21 X 864mm on the other side (refer Fig 2). This
through hole is used for drainage of condensate water from the valve.
The process of deep drilling has some technological constraints; as a long drill, it tends
to camber when connected to the spindle and vibrate on operation. Therefore it is very
difficult to attain high accuracy. In the present case, two holes of different sizes are to
be drilled from both ends by rotating the machine table and the holes have to coincide
perfectly; moreover the wall of the diffuser is very thin, so any slight misalignment of
the drill will puncture the inner surface which will result in rejection of the component.
Therefore a fixture to guide and eliminate the vibration in drills was needed.

OBJECTS OF THE INVENTION
1. The object of invention was to develop a fixture for deep drilling which eliminates
possibility of any misalignment during drilling operations.
2. Another object of the invention was to develop a fixture that for establishing a
process set up for through and blind holes also for constant size holes and variable size
holes.
3. A further object of the invention was to design a fixture in such a way that it uses
standard components that are readily available in shop.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1 - IV/CV casing assembly comprising the diffuser which is a special type of job in
the subject case.
Fig 2 - Hole location in diffuser which is the subject job.
Fig 3 - Schematic diagram of the fixture
Fixture Components comprising:-
Fig 4a - Base plate (1)
Fig 4b - Stud (2)
Fig 4c - Locking nut (3)
Fig 4d - Locking screw (4)
Fig 4e - cap nut (5)
Fig 4f - Guide bush (6)

Fig 4g - Guiding nut (7)
Fig 5 - Photographic view of the fixture
Fig 6 - Fixture with job on the machine
SUMMARY OF THE INVENTION
One of the IV/CV 660/700/800MW component diffuser has a hole of length 1764mm
which has dia. 25 up to 900mm and dia 21 for the remaining length (Refer Fig 2)
The constraint for deep drilling is the camber on drill and the vibration while drilling.
The job requirement is that the hole should align perfectly. As the component is of high
accuracy and value, any misalignment while machining could result in rejection of job
and delay in project at site. Therefore the development fixtures eliminate the
aforementioned possibilities of error.
DETAILED DESCRIPTION OF THE INVENTION
The fixture comprising:
- a base plate (01) over which the fixture is erected
- a stud (02) having both ends threaded is fixed on the threaded base plate (01) at the
1st end so that it stands vertically
- a locking nut (03) having central inner thread is mounted over the external thread at
the 2nd end of the stud (02). The locking nut (03) is also having plurality of threaded
holes in radial directions for locking the cap nut (05) by the locking screw (4) at
particular height and angle.

- a cap nut (05) assembled over the stud (02), having the cap nut (5) having an
internal thread for height and angular adjustment.
- a guide nut (07) having internal thread is welded over cap nut (05)
- guide bush (06) having variable internal diameter for guiding various sizes of drill, has
fixed external thread for fitting into the internal thread of guide nut (07).
The centre line of the guide bush (06) in adjusted in such a way that it is aligned with
the centre line of the hole to be drilled in the job.
The fixture can be used for drilling of different sizes of holes by changing the guide
bush (06). The internal diameter of the guide bush (06) varies according to the drill size
whereas the external diameter of the guide bush (06) remains the same.
The guide bush (06) is made of soft material like bronze.
PROCESS OF DEEP DRILLING ON DIFFUSER' FOR IV
1. The job is on two 'V' blocks and then aligned and clamped on the machine table by
aligning it from both ends and marking of centre for the holes to be drilled is done.
2. The fixture is clamped in front of the hole marking, the bronze bush (6) is fitted in
the nut (7). The soft material is used because it will not damage the drill (if misaligned)
and will dampen the vibration more effectively.
3. The hole is drilled through the bush (6) up to the marking. The hole in the bush (6)
is drilled at the machine so as to align it with reference to the machine spindle axis.
4. After that the drill location is checked whether it is coming at the marking point of
the hole, then the drilling is initiated.

5. Drill is fed at 4-5mm cut and then retracted outside the job to clean the chips and
necessary cooling of the drill and job.
6. After the desired length of the dia 21mm is drilled, the job is reversed by rotating the
machine table and the same process is repeated for drilling dia 25mm hole after
alignment.
7. Both the holes coincide as per the design requirement which proves the competency
of the fixture.
BENEFITS INCURRED
Productivity: This method enables deep drilling in the jobs with high accuracy and
reduces the cycle time. This method diminishes risk of damage to the drill and job while
using long drills.
Time take (drilling + pecking + setting fixture) =17hrs
1. Quality: By carrying out the drilling operation with the fixture high accuracy on the
varying size hole is achieved. The rejection of job due to any misalignment is avoided
and good finishing on the drill hole is attained.
2. Utility of the design: Turbine machine shop has many horizontal borers and there are
many components that require deep drilling operation as per technological requirement.
The fixture can be used on all such jobs on all the horizontal boring machines. The
designed fixture sets up the benchmarking method for drilling deep holes.
3. Capacity enhancement: Previously the 'diffuser' was bought out item (BOI) but with
technological development this component can be manufactured in house.
4. Safety: The fixture guides and supports the drills so that the operator won't have to
manually align the drill every time it retracts to clear the chips. This makes the process

safer and it avoids any possibility of failure of drill due to vibration which could seriously
injure the operator and could damage the workpiece.
Time Saving: In a conventional setup, the operator has to align the drill manually every
time the drill is withdrawn for clearing the chips. This consumes lot of effective time
and increase the time cycle for job completion. With the implementation of the fixture,
operator needs not to adjust the drill in every pass which saves a lot of machining time.
6. Technological Improvement: By the use of fixture, developed not only a machining
process set up in established for one component but it can be used on all such jobs
where deep holes are to be machined for various components on various machines.

WE CLAIM:
1. a guiding and vibration dampening fixture for long drill in deep drilling operations
comprising:
a base plate (1) having internal thread over which a stud (2) having external thread at
both end is erected;
one end of the stud (2) is fitted on the internal thread of base plate (01);
a locking nut (3) having internal thread is fitted on the other end of the stud (2);
a cap nut (05) having internal thread placed on the 2nd end of the stud (2) over the
locking nut (3);
a guiding nut (7) having internal thread is welded over the head of cap nut (5);
a guide bush (6) having external thread is fitted over the guiding nut (7);
characterized in that the guide bush (6) guides the drill wherein the cap nut (5) having
internal thread maintains the angular and height adjustment.
2. The fixture as claimed in claim 1 wherein the guide bush (06) is made of softer
material like bronze.
3. The fixture as claimed in claim 1 wherein the guide bush (6) having a fixed diameter
of external threaded, but variable diameter of internal thread to suit drills of various
sizes according to the job requirement.
4. The fixture as claimed in claim 1 wherein the locking nut (3) having plurality of
threaded holes in radial directions for locking of nut at different height of the stud (2)
with the help of locking screw (4).

5. A process of deep drilling of holes by guiding and vibration dampening fixture
comprising:
- holding the job on two 'V' blocks, aligning it from both ends with marking of centres
for the holes to be drilled and then clamping in that position;
- fitting in the guide bush (06) on the guide nut (7) for the required drill size;
-adjusting the height and angle of the cap nut (5) by rotating the cap nut and then
locking the nut (3) by tightening the screw (4) in that position such that the drill is
aligned with the mark of centres at both ends.
- drilling the job up to a distance of 4-5mm and then retracting it for removal of chips
from the hole and cooling of the drill and the job
- continuing the drilling and retracting operation in the manner as previously till the
whole length of drilling is completed

- reversing the job on the other side of marking and aligning the job in the same
manner with the marking
- clampings and then drilling the job for other dimension of drilling holes;
- performing the drilling operation in step for a length of 4-5mm at a time, retracting
the drill, removing the chips, allowing setting time for cooling of the job and then
performing further drilling till the drilling is completed for the required length.