Title: A clamping device for root and shroud grinding of non-magnetic
blades.
FIELD OF THE INVENTION:
The present invention is related to a device for clamping non-magnetic blades
during grinding on surface grinding machine. More particularly the present
invention is related to a device which is capable to clamp the root & shroud of
non-magnetic blades & can be placed on an electromagnetic sine table of
surface grinding machine.
BACKGROUND OF THE INVENTION:
Steam turbine consists of 3 modules HP, IP & LP. Stream passes through all
the modules and converts thermal energy (high pressure & high temperature)
of working fluid in to mechanical energy.
In Supercritical steam turbine HP & IP module blades of initial stages have to
encounter high pressure and temperature. Therefore, in these stages super
alloys should be capable to achieve the design performance during the service
condition. Super alloys (nomonic 80A steel) used in these blades are non-
magnetic.
The turbine blades needs to be ground at root & shroud on suction side to
achieve the recommended assembly conditions.
Grinding of the blades needs proper clamping in order to achieve the following
assembly requirements:-
a) Pitch correction for achieving recommended design interference for lock
blades in each stage of turbine rotor & casing blading.
b) To improve the feeler gap clearance between adjacent blades in each
stage.
c) To achieve pre-stressing of the fitted blades as per design
recommendations.
d) To achieve the recommended flowpath of blades to be used in each stages.
In the past, in subcritical steam turbine sets, material of blades was magnetic
where the blades were directly clamped on electromagnetic sine table during
grinding operation.

Therefore, in the case of non-magnetic blades there is a need of a device
which is capable to hold securely the root & shroud of blades & can be placed
on an electromagnetic sine table during grinding on surface grinding machine.
OBJECT OF THE INVENTION:
The object of the present invention is to provide a device which can clamp the
root & shroud of non-magnetic blades on electro magnetic sine table.
Another the object of the present invention is to provide a device which is
portable and light in weight and rigid enough to sustain themachining forces
while using on surface grinding machine.
A further object of the present invention is to provide a device which is
adjustable to accommodate the different length & cross-sections of blades.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Fig.1- shows the Clamping device for root and shroud grinding of non-magnetic
blades according to present invention which comprises of: -
(a) Fixed jaw or base of the fixture (1), (b) Adjustable jaw (2), (c)
Center guide (3), (d) Spindle (4),(e) Side bracket (5),(f)Root clamp
(6),(g)Shroud clamp (7), (h)End plate (8).
Fig.2(a)- shows the shows the sectional view of the device with blade
Fig 2(b)- shows the isometric view of the device without blade.
Fig.3 - shows the different views of steam turbine blade to be ground. The
blade is rhomboidal in cross section having rhomboidal angle is
defined by angleα. Angle β1 has to be ground on root of blade
having thickness-t1 & β2 on shroud having thickness-t2.

Fig.4- shows the fixed jaw (1) acting as base of the fixture. A step having
dimension L1xW1XH1 provided on the right side of the jaw to rest the
blade root. Depth of slot (H1) should be less than the thickness of the
root (k1) of the blade. A slot of dimension T1 length Z is made to
provide the passes for spindle. Hole diameter D1 is made at the end
of slot to provide the support to spindle and maintain its axis.
Fig.5 (a) - shows the side bracket (5). The Side bracket provide the guide
support to the spindle and prevent the movement of spindle in
horizontal direction.
Fig.5 (b) - shows the spindle (4). Square threads are machined on the spindle.
Diameter D2 provided on the spindle, it rests in hole diameter D1 in
fixed jaw (1) to maintain the axis of the spindle parallel to base of
fixed jaw. Diameter D6 on spindle rests in the hole diameter D5 on
side bracket to provide a bearing surface to the spindle.
Fig.6(a) - shows the center guide (3). It is used to provide the linear motion to
the moveable jaw. Center guide is provided with diameter D3, &
square threads are machined on it.
Fig.6(b)- shows the root clamp & shroud clamp, angle α is machined on the
one end of clamps according to blade rhomboid angle.
Fig.7(a) - shows the adjustable jaw (2). Shroud of blade rests on the
adjustable jaw. A step having dimensions L2xW2xH2 is provided
on jaw. Depth of step should be less than the shroud thickness (k2)
of blade to ensure the proper grinding of blade instead of device. A
hole diameter of D4 is provided at the bottom of the adjustable jaw.
Center guide (5) diameter D3, push fitted in the adjustable jaw
diameter D4.
Fig 7(b) - shows an end plate. End plate is made of soft material & screwed on
the butting surface of the adjustable jaw.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION:-
According to the invention there is provided a Clamping device for root and
shroud grinding of non-magnetic blades according to present invention which
comprises of: -
Fixed jaw (1)
Adjustable jaw (2)
Center guide (3)
Spindle (4)
Side bracket (5)
Root clamp (6)
Shroud clamp (7)
End palate (8)
As shown in fig.1 assembly view of the device. The jaws of the device are
sufficiently opened to accommodate the length of the blade to be ground. Root
of the blade placed on the fixed jaw (1) having step dimensions H1xL1xW1.
depth of step H1 should be less than the thickness of blade root. Shroud of
blade is placed on adjustable jaw (2). Depth of the step on adjustable jaw H2
should be less than the blade should thickness. Fixed jaw (1) also provides the
base to the device. A center guide (3) is fitted in adjustable jaw (2) by using
hole diameter D3/D4. The whole assembly is placed on fixed jaw (1) by using
guided dimensions T2/T4. Spindle (4) passes through the center guide (3) &
one end of spindle rests in fixed jaw (1) by using hole dimensions D2/D1. Side
bracket (5) is screwed on the other end of fixed jaw (1) to support the spindle
(4). By rotating the spindle (4), adjustable jaw slides on fixed jaw (1) and can
be adjusted at any position to accommodate the different lengths of the blade.
Blade is placed on the clamping device with pressure side facing downward in
such a way that the root of blade should be on the fixed jaw (1) and the shroud
on adjustable jaw (2) (see fig.1). position of one side shroud & root clamp are
fixed in such a fashion that the center axis of the blade remains perpendicular

to the butting surface of fixed jaws. Now the adjustable jaw (2) is moved by
rotating the spindle (4) towards the fixed jaw (1), resulting the blade to firmly
hold on the device. By using feeler of 0.02mm ensure the resting of blade at
shroud and root pressure side faces with the resting surface of the jaws. After
ensuring the butting, other side root clamp (6) & shroud clamp (7) are
tightened.
To place the device with blade for grinding on magnetic sine table of the
surface grinding machine such that the fixed jaws of the device come first
during the approach of grinding wheel during each grinding stock.
For pitch correction or taper correction of the blade, device is to be placed
parallel to the magnetic sine table. For feeler correction the device is to be
placed at angle to the magnetic sine table as required.
Fig.2(a) shows the shows the sectional view of device with blade.
Fig (2b) shows the isometric view of device without blade.
Fig.3 shows the different views of steam turbine blade to be ground. Blade is
having rhomboidal cross section for which rhomboidal angle is defined by α.
Angle β1 has to be ground on root of blade having thickness-t1&β2 on shroud
having thickness-t2.
Fig.4 shows the fixed jaw (1). A step having dimension L1xW1XH1 provided
on the right side of the jaw to rest the blade root. Depth of slot (H1) should be
less than the thickness of the root (k1) of the blade. A slot of dimension T1
length Z is made to provide the passes for spindle. Hole diameter Dl is made at
the end of slot to provide the support to spindle and maintain its axis.
Fig.5 (a) shows the side bracket (5). Side bracket provide the guide support to
the spindle and it prevent the movement of spindle in horizontal direction.

Fig.5 (b) shows the spindle (4). Square threads are machined on the spindle.
Diameter D2 provided on the spindle, it rests in hole diameter D1 in fixed jaw to
maintain the axis of the spindle parallel to base of fixed jaw. Diameter D6 on
spindle rests in the hole diameter D5 on side bracket to provide a bearing
surface to the spindle.
Fig.6(a) shows the center guide (3). It is used to provide the linear motion to
the moveable jaw. Center guide id provided with diameter D3, & square
threads are machined on it.
Fig.(6b) shows the side clamps, angle a is machined on the one end of clamps
according to blade rhomboid angle.
Fig.7(a) shows the adjustable jaw (2). Shroud of blade rests on the adjustable
jaw. A step having dimensions L2xW2xH2 is provided on jaw. Depth of step
should be less than the shroud thickness (k2) of blade to ensure the proper
grinding of blade instead of device. A hole diameter of D4 id provided at the
bottom of the adjustable jaw. Center guide (5) diameter D3, push fitted in the
adjustable jaw diameter D4.
Fig 7(b) shows an end plate. End plate (8) is made of soft material & screwed
on the butting surface of the adjustable jaw.

We Claim
1. A clamping device for root and shroud grinding of non-magnetic
blades comprising of: -
a fixed jaw (1) acting as base of the fixture;
an adjustable jaw (2) fitted over a base (1) through a centre guide (3) using
hole diameter D3/D4 and by using guided dimension T2/T4;
a spindle (4) mounted over the base (1) in such a manner that one end
diameter (D2) of the spindle (4) rests on the hole diameter (D1) in fixed jaw
(1) and the other end diameter (D6) of the spindle (4) rests in the hole
diameter (D5) on side bracket (5) making the axis of the spindle being
parallel to the base of fixed jaw;
the said spindle (04) disposed to pass threaded hole of the centre guide
(3) characterized in that the adjustable jaw (2) can be brought nearer or
away from the fixed jaws (1) so that the adjustable jaw slides on the base
and can be adjusted at any position to accommodate the different lengths
of the blade when the shroud clamp (7) and root clamp (6) ensures perfect
butting of contact surfaces of the turbine blade in the shroud side and root
sides with the clamping jaws.
2. The clamping device as claimed in claim 1, wherein the spindles (4) have
matching square threads matching with the same in the hole of centre
guide (3) for to and fro movement of adjustable jaw (2).
3. The clamping device as claimed in claim 1, wherein the spindles (4) are
made of hardened and tempered alloy steel to prevent wear and tear.
4. The device as claimed in claim 1, which is portable and light in weight and
can be easily carried and removed after its application.
5. The device as claimed in claim 1, which is adjustable to accommodate the
different length and cross-sections of blades.