FIELD OF INVENTION
The field of invention relates to a device and method to carry out drilling
operation of Fan blade locking holes on a rotor of a large size turbogenerator
upto 500 MW.
BACKGROUND OF THE INVENTION
A rotor is first machined for making slots. After making slots the rotor is shifted
to a horizontal boring machine for carrying out the drilling of fan blade locking
holes. There are 50 holes on each side of the rotor (Turbine side and Generator
Side ) to be drilled. All holes are of 8.5 mm diameter. Perpendicular to this
holes there is a hole having thread of 60X 2 mm size. Bottom of the blade is
locked through this (8.5mm) hole by a grub screw which sets the blade at an
angle of 18 degree. The rotor is placed on rollers for drilling operation. The
rollers are pre set as per the length of the rotor on machine bed. The rotor is
set for X,Y,& Z axis with respect to machine axis. A Specific drilling head is
mounted on the machine spindle. The assembly of drill head takes on an
average, three hours. Next a jig is fixed in Fan blade hole of M60 on the rotor to
guide the drill for drilling 8.5 mm dia hole. A drill of 8.5 mm X 300mm long is
mounted on the drill head. The drill moves through the jig to make 8.5 mm dia
hole on rotor face. The configuration of the jig and the fixation of the jig is such
that only two holes are possible to be drilled in this manner. For drilling another
two holes, the jig is opened from this position and fixed with next blade hole to
drill next two holes. In all 25 settings are done to drill 50 holes in one side.
However tool setting is done 50 times to drill these 50 holes. The whole

hours. The rotor is then lifted and its other side is placed before the drilling
head to carry out the drilling of 50 holes on this side. This takes another
additional four hours.
The above arrangement of drilling operation for drilling 100 holes on two sides of
a rotor has many problems and disadvantages.
The distance of the Jig face to 8.5 dia hole is 80 mm which means the Overhang
of the drill is 80 mm. This creates a problem of vibration at the time of drilling
operation resulting in shifting of holes as well as damaging straightness of holes.
This again results in breaking of tap while threads are made.
The drill head is of size 700 mm in length, 300mm in diameter and weighs
200kg. Crane in needed to fix this drill head on the face of ram and fix the
spindle of horizontal machine. This total operation takes a very long time.
After making 50 holes on one side, the rotor is reversed to make holes on other
side. This operation of reversing of rotor takes on an average four hours.
Presetting of roller on machine bed also takes 3 hours.
The length of drilling head is 700 mm and the drill used is also of 300 mm
length. Hence to avoid chattering of holes and the breakage of drill, feed rate is
fixed at 90-100 rpm instead of 1000 rpm that could be possible with M8 dia drill.
This results ten times higher cycle time in drilling the holes.
Also risk of accident is high as the operator uses stool to make up the height to
see the location of drill during drilling operation. In addition to this the drill
length being very long (300mm) there is always a possibility of accident when
drill breaks during operation.

OBJECTS OF INVENTION
It is therefore an object of the invention to propose a device and method for
drilling fan blade locking holes on a rotor of a large size turbogenerator which
eliminates the disadvantages of Prior art.
Another object of the invention is to propose a device and method for drilling fan
blade locking holes on a rotor of a large size turbogenerator which reduces time
cycle of the operation.
A still another object of the invention is to propose a device and method for
drilling fan blade locking holes on a rotor of large size turbogenerator which
reduces costs of operation
A further object of the invention is to propose a device and method for drilling
fan blade locking holes on a rotor of a large size turbogenerator which ensures
safety of operation.
A still further object of the invention is to propose a device and method for
drilling fan blade locking holes on a rotor of a large size turbogenerator which
reduces the overhang of the drill ensuring production of straight holes.
SUMMARY OF INVENTION
Accordingly, there is provided a device and method for drilling fan blade locking
holes on a Rotor of a large size turbogenerator, the rotor being placed on a
preset rollers. The rollers are present as per the length of the rotor on the
machine bed for its height considering three axis X,Y and Z with respect to
machine axis. The device consists of a universal mounting disc (10) having an

outer housing (11) fixed on top of it through four matching holes and attached
to a base plate (20). The base plate (20) is mounted on roller stand with support
plates (19). The outer housing houses the slide (12) having a hemispherical
shape with top side flat. A tool clamp (14) is fixed on the top of the slide (12) by
screws. The two ends of operating lever short arm (16) is hinged with
outerhousing (11) and long arm (15) is hinged with slide (12). The slide (12)
being fixed to the operating lever long arm (15) at one end provides movement
of the tool when the lever (15) is moved. Two guide plates (13) fixed on both
side of the outer housing (11) of the device covering part of the slide (12) to
stop the circular movement of the slide (12) in both side. A locating device (B)
designed to reduce the length of overhang part of the drill is fitted in the hole
M60X2 on sphere diameter of the turbogenerator rotor where blade is fitted. A
hand drill machine having the tool fixed to its chuck, drill the required holes, the
slide (12) being moved in axial direction to provide the feed of the tool for the
required length of the holes to be drilled on the face of turbogenerator rotor.
BRIEF DESCRIPTION OF THE DRAWING
Fig 1 - It shows an assembly of the drilling device (A).
Fig 2 - It shows different items of the device.
Fig 3 - Shows the locating device with turbogenerator Rotor
Fig 4 - Shows the new locating device (B).
An exemplary embodiment of the invention as depicted in the accompanying
drawing will now be explained in details. However there can be several other
embodiments all of which are deemed covered by this specification.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION

As shown in fig 1, a drilling device (A) for drilling fan blade locking holes on a
rotor of a large size turbogenerator comprises of a universal mounting Disc (10)
on top of which a outer housing (11) is bolted, the said outerhousing having
hemispherical slide (12) capable of sliding in a half-circular contour of the
housing (11) with radius for example 25mm. The universal mounting disc (10) is
attached to a base plate (20) having length for example of 700m and breadth for
example 120 mm and'weight for example of 5kg for easy movement. The base
plate (20) is fixed with both side column of roller stand by at least three support
plates (19) tightening the base plate with bolts. The rotor is placed on a plurality
of rollers which are preset as per the length of rotor on machine bed. The rotor
is set for X,Y & Z axis with respect to machine axis. Three supports (19) are
made to fix both ends of the base plate (20) with roller column. Two plates are
attached on top of the base plate (20) while the third plate is fixed with the
bottom of the base plate (20). The universal mounting disc (10) fixed with the
base plate (20) with a threaded bolt can remain stationary as well as can rotate
the complete working parts of the drilling device to any circular position. This
helps to set the drilling device in minimum time in perpendicular position to the
turbogenerator Rotor wherein 50 holes are being drilled. All four holes of the
disc (10) are made to fix the outer housing (11) of the device. The outer
housing (11) is a stationery part and its length is so designed that the drill and
slide can move to complete the locking holes in the Rotor. The inside of housing
(11) has hemi-spherical shape matching with the slide. The two ends of
operating lever short arm (16) is hinged with outerhousing and operating lever
long arm (15). The slide (12) being fixed to the operating lever long arm (15) at
one end provides movement of the tool clamp (14) when the lever (15) is
moved. The outer housing (11) is made of cast iron that helps in slide (12)
movement. The slide (12) which is fixed to the outer housing (15) of the device,
moves the tool clamp (4) holding the tool to drill the locating holes. To stop the
circular movement of the slide (12) two slide guide plates (13) are fixed on both

side of the outer housing (11) of the device (A). A clamp (14) to hold the tool
holder is fixed with the slide (12). As shown in fig 1, two hinges (17) are used to
fix the arms of the operating lever (15). This helps in operating the lever with
less effort and move at ease.
A locating device (B), as shown in fig 4 is a part of this drilling device. This new
locating device providing guidance to the drill is designed to reduce the length of
the overhang part of the drill by 97% resulting very less vibration during drilling
operation that almost reduces the non conformity of holes due to vibration of
long overhang portion of the drill. This locking device (B) is fitted on the outer
portion of the turbogenerator rotor where blade is fitted by a lock nut.
A mounting and adjusting screw (18) is used to mount the main drilling device
and also to align the drill tool by adjusting this screw in vertical direction. Thus
the drill is adjusted as per the hole to be drilled.
The tool holder fixed in the clamp (4) and carrying the drill is connected to a
hand operated drilling machine. The drilling operation is performed with the help
of this machine and drilling device when the drill passes through the locating
device before it reaches the rotor.

WE CLAIM
1. A method for drilling fan blade locking holes of a large size turbogenerator
rotor comprising:
The drill being fixed in the tool clamp (14) moves along with the slide;
The operating lever long arm and short arm (15,16) moves the slide and
the drill towards the rotor;
The drill Is aligned with the holes by means of a mounting and adjusting
screw (18);
The drill is guided by the locating device being fitted to the roller stand on
the outer portion of the turbogenerator rotor;
2. A method for drilling fan blade locking holes of a large size turbogenerator
as claimed in claim 1, wherein the drill making the holes receives the
rotational force from the hand drilling m/c.
3. A device (A) for drilling fan blade locking holes of a large size
turbogenerator rotor comprising:
a universal mounting disc (10) having an outerhousing (11) fixed on top
of it, is attached to a base plate (20);
a plurality of support plates (19) for fixing the base plate (20) with side
columns of roller stand;

a slide (12) having a tool clamp (14) mounted on its top being fixed in the
outerhousing (11), said slide being joined with an operating lever (15) is
hinged at two places (17); and
a locating device (B) to guide the drill is fitted to the roller stand on the
outer portion of the turbogenerator.
•4. A device (A) for drilling fan blade locking holes of a large size
turbogenerator rotor as claimed in claim 3, wherein the configuration of
the bottom of slide (12) is of hemispherical shape.
5. A device (A) for drilling fan blade locking holes of a large size
turbogenerator rotor as claimed in claim 3, wherein two guide plates (13)
arrest the circular motion of the slide (12).
6. A device (A) for drilling fan blade locking holes of a large size
turbogenerator rotor as claimed in claim 3, wherein the locating device (B)
provides an overhang of the drill up to 2mm.

A device (A) for drilling fan blade locking holes on a rotor of a large size turbogenerator consists of a universal mounting disc (10) having an outerhousing (11) foxed on top of it is attached to a base plate (20). This base
plate (20) along with a plurality of support plates (19) is fixed to the side columns of roller stand. A slide (12) with its bottom having a hemispherical shape is fixed to the outerhousing (11). The slide (12) carrying the tool clamp (14) is attached to an operating lever (15) which is hinged at two place. The
slide (12) along with the tool clamp (14) can move to and fro with the help of the operating lever (15). A locating device (B) being fitted to the roller stand on the outer portion of the turbogenerator provides guidance to the drill and is so designed that overhang of the drill is upto 2 min and that reduces the vibration
of the drill. The drill is aligned with the holes by means of a mounting and adjusting screw.