CLIAMS:We claim:
1) A compound angle adjustment fixture (100) for pitch milling operation, comprising:
a) a seesaw block (112) comprising at least one hole (H3) on a flat face;
b) a base block (110) coupled to the seesaw block (112) via at least one hole (H2) complementary to the at least one hole (H3), wherein the base block (110) comprises at least one hole (H1) on its either ends;
c) a side support block (114) comprising a hole (H4) and a gap (G1) adjustably separating an upper portion of the side support block (114), wherein a pair of the side support blocks (114) are adapted to couple with the base block (110) via at least one hole (H6) on the side support block (114) and the at least one hole (H1) of the base block (110);
d) a connecting block (116) comprising a cylindrical portion (C1) on either ends and a slot (S1), wherein the cylindrical portion (C1) is couplable with the hole (H4) in each of the pair of side support blocks (114);
e) a tenon block (124) comprising at least one hole (H13);
f) a sliding block (118) comprising a step (St1) and a slot (S2), wherein the slot (S2) is adapted to couple the tenon block (124) via at least one hole (H7) and the at least one hole (H13), the tenon block further adapted to movably couple with the connecting block (116) via slot (S1), and wherein the sliding block (118) further comprises a hole (H8);
g) a clamping pad (122) comprising at least one hole (H12) therein; and
h) a clamp (120) coupled with the clamping pad (122) via at least one hole (H10) and the at least one hole (H12), wherein the clamp (120) is adapted to firmly hold a workpiece on step (St1) by means of a hole (H9) adjustably engaged with the sliding block (118) via the hole (H8), the clamp (120) integral with the clamping pad (122) maintained perpendicular to the workpiece by means of fasteners passing through a hole (H11).

2) A compound angle adjustment fixture (100) for pitch milling operation as claimed in claim 1, wherein said clamp (120) adapted to adjustably engaged with the sliding block (118) by means of a dowel bolt (126).

3) A compound angle adjustment fixture (100) for pitch milling operation as claimed in claim 1, wherein the flexibility of said sliding block (118) to lock at different positions on the connecting block (116) facilitates in accommodating the workpiece of different heights.

4) A compound angle adjustment fixture (100) for pitch milling operation as claimed in claim 1, wherein said clamp (120) integral with said clamping pad (122) adapted to adjustably engaged with the sliding block (118) facilitates in accommodating the workpiece of different widths.

5) A compound angle adjustment fixture (100) for pitch milling operation as claimed in claim 1, wherein said work piece is tightly held between the step (St1) of the sliding block (118) and the clamping pad (122).

6) A compound angle adjustment fixture (100) for pitch milling operation as claimed in claim 1, wherein said work piece is skewed radial entry T-root blade (136).

7) A compound angle adjustment fixture (100) for pitch milling operation as claimed in claim 1, wherein the pair of the side support blocks (114) are adapted to couple with the base block (110) via at least one of nuts, bolts, screws, pins, or any combinations thereof.

8) A compound angle adjustment fixture (100) for pitch milling operation as claimed in claim 1, wherein the fasteners comprise at least one of nuts, bolts, screws, pins, or any combinations thereof.

9) A method of performing a pitch milling operation on a compound angle adjustment fixture (100), said method comprising the steps of :
a) placing a seesaw block (112) of a compound angle adjustment fixture (100) between jaws of a vice (134) located on a bed of a CNC machine and locked in position by tightening the jaws of the vice (134);
b) placing a skewed radial entry T-root blade (136) on a step (St1) of a sliding block (118) with tapered face (T) of root surface facing upwards and tightly held between a clamping pad (122) and vertical face of the step (St1) of the sliding block (118);
c) mounting a dial gauge (DG) on a spindle of a CNC machine and a sensor button of the dial gauge (DG) adapted to touch at extreme end on root surface of the skewed radial entry T-root blade (136) along y-axis direction by doing adjustments to the bed of the CNC machine, said sensor button of the dial gauge (DG) in contact with root surface of the skewed radial entry T-root blade (136) adapted to move from one extreme end on root surface of the skewed radial entry T-root blade (136) to other extreme end along y-axis direction by movement of the bed of the CNC machine and deviations and direction of deviations of a pointer of the dial gauge (DG) recorded;
d) performing counter adjustments by trial and error to the seesaw block (112) of said compound angle adjustment fixture (100) based on the deviations and direction of deviations of the pointer of the dial gauge (DG), by tapping said compound angle adjustment fixture (100) up and down, by opening the jaws of the vice (134) marginally and locking said seesaw block (112) in a position where flatness on root surface of the skewed radial entry T-root blade (136) along y-axis direction is within the tolerance limits by closing the jaws of the vice (134);
e) touching said sensor button of the dial gauge (DG) at extreme end on root surface of the skewed radial entry T-root blade (136) along x-axis direction by doing adjustments to the bed of the CNC machine, said sensor button of the dial gauge (DG) in contact with root surface of the skewed radial entry T-root blade (136) adapted to move from one extreme end on root surface of the skewed radial entry T-root blade (136) to other extreme end along x-axis direction by movement of the bed of the CNC machine and deviations and direction of deviations of the pointer of the dial gauge (DG) recorded; and
f) performing counter adjustments by trial and error to a connecting block (116) of said compound angle adjustment fixture (100) based on the deviations and direction of deviations of the pointer of the dial gauge (DG), by rotating said connecting block (116) clockwise and anti clockwise, by loosening fasteners provided in hole (H5) of a pair of side support blocks (114) and locking said connecting block (116) in a position where flatness on root surface of the skewed radial entry T-root blade (136) along x-axis direction is within the tolerance limits by tightening said fasteners.

10) A method of performing a pitch milling operation on a compound angle adjustment fixture (100) as claimed in claim 9, wherein said pitch milling operation is performed once flatness within tolerance limits of +/- 20 microns is achieved on x-y plane on root surface of the skewed radial entry T-root blade (136).
,TagSPECI:FIELD OF THE INVENTION:
The present invention relates to a field of tools. Particularly, the present invention relates to a fixture to help in performing pitch milling operation on an angular root surface of the blades with precision.

BACKGROUND OF THE INVENTION:
The term compound angle used in this specification refers to a combination of two or more angles provided on a root surface of a blade.

Figures 1(a) and 1(b) illustrate top views of a straight radial entry T-root blade and a skewed radial entry T-root blade respectively.

It can be inferred from figure 1(b) that skew angle is provided to a root of the blade to accommodate the shape of the profile of the blade. Moreover, skew angle on the root of radial entry T-root blades provides more contact surface area at mating portion of two skewed radial entry T-root blades thereby holding the blades firmly in the rotor disc of a turbine.

Figure 2(a) illustrates an isometric view of skewed radial entry T-root blade.

Figure 2(b) illustrates a side view of skewed radial entry T-root blade of figure 2(a).

Figure 3 illustrates an assembled view of skewed radial entry T-root blades.

It is evident from figure 2(b) that both surfaces of the root of the skewed radial entry T-root blade are skewed. One surface of the root of the skewed radial entry T-root blade has flat face F and other surface of the root of the skewed radial entry T-root blade has tapered face T. The surface of the root of one skewed radial entry T-root blade on its tapered face T is adapted to mate perfectly with the surface of the root of other skewed radial entry T-root blade on its flat face F as shown in figure 3 thereby providing a small tilt to the other skewed radial entry T-root blade in such a way to form cyclic surfaces during assembly of skewed radial entry T-root blades on to a disc of a rotor.

Figure 4 illustrates an isometric view of skewed radial entry T-root blades assembled on to a disc of a rotor without a closing blade.

During machining of the skewed radial entry T- root blades, an excess material of +0.05mm than the desired thickness is kept on every root of the skewed radial entry T-root blades on their tapered face T purposefully such that the disc of the rotor would not be left with a space that is more than the thickness of the closing blade leaving a gap therein.

Due to provision of excess material on the root of the skewed radial entry T-root blades, the space left out for the closing blade in the disc of the rotor after assembling of all the blades may not be sufficient to accommodate the closing blade. In this context, the closing blade can be accommodated in the space left out in the disc of rotor by means of two methods:
1) by removing the material on the root of the closing blade and bringing the thickness of the closing blade to accommodate in the space left out in the disc of the rotor; and
2) by removing material of uniform thickness from the blades to provide the extra space in the disc of the rotor that is required to accommodate the closing blade.

The method of removing the material only on the closing blade results in the concentration of stress on the closing blade and the probability of failure of the closing blade during rotation of the rotor is very high.

Therefore, traditionally, turbine OEM’s follow the method of removing uniform thickness of material on multiple blades. To remove uniform thickness of material on the blades, an operation called pitch milling operation is performed.

The uniform thickness of the material that is to be removed on the blades is calculated by the following formula:

Uniform thickness of material that Extra space in the disc of the rotor that is
required to accommodate the closing blade
=
is to be removed on the blades Number of the blades on which the excess
material is to be removed

Some techniques have been disclosed in the prior art for machining on compound angle surfaces.

US Patent no. 2991668 filed on September 12, 1960 titled “Universally adjustable work holder and drill jig fixture” discloses a work holding and drill jig fixture which is capable of supporting a workpiece at any desired compound angle relative to the drill jig. The work holder and drill jig fixture disclosed in this prior art has lot of disadvantages like not holding the workpiece firmly, difficulty in machining on the work piece, not designed particularly for usage on blades as workpieces, non uniform removal of material on the workpiece, not removing the material precisely from the workpiece and not suitable for mounting on bed of CNC machines.

Therefore, there is felt a need for development of a compound angle adjustment fixture to overcome the drawbacks of prior art and thereby perform uniform pitch milling operation on the root surface of skewed radial entry blades with precision.

SUMMARY OF THE INVENTION:
In accordance with the present invention a compound angle adjustment fixture for pitch milling operation is provided, said fixture comprising:
(i) a seesaw block (112) provided with a rounded face at its base, the seesaw block
(112) provided with a set of threaded holes (H3) on its top face;
(ii) a base block (110) provided with a set of threaded holes (H2) on its top face
complementary to the set of threaded holes (H3) of the seesaw block (112), the base block (110) provided with through threaded holes (H1) on its top face, the base block (110) mounted on the seesaw block (112) such that the set of threaded holes (H2) of the base block (110) are in line to the set of threaded holes (H3) of the seesaw block (112) and locked in position by means of a plurality of screws (128) passing through the set of threaded holes (H2) of the base block (110) and the set of threaded holes (H3) of the seesaw block (112);
(iii) a pair of side support blocks (114) provided in the form of steps on either side
with a through hole (H4) provided at their center, the pair of side support blocks (114) provided with a gap (G1) perpendicularly from their top face to the through hole (H4) dividing upper portion of the pair of side support blocks (114) into two halves, the pair of side support blocks (114) provided with a through threaded hole (H5) on vertically upright portion of the step passing through each of two halves, the pair of side support blocks (114) provided with holes (H6) on either side at base portion of the step, the pair of side support blocks (114) mounted on the base block (110) such that the holes (H6) of the pair of side support blocks (114) and the through threaded holes (H1) of the base block (110) are in line to each other and locked in position by means of a plurality of bolts (130) passing through the holes (H6) of the pair of side support blocks (114) and the through threaded holes (H1) of the base block (110);
(iv) a connecting block (116) comprising a block with cylinders (C1) attached at either ends, the connecting block (116) provided with a slot (S1) therein of predetermined width and depth, the connecting block (116) adapted to mount on the pair of side support blocks (114) by means of cylinders (C1) passing through the through hole (H4) of the pair of side support blocks (114) and locked in position by means of the plurality of bolts passing through the through threaded hole (H5) of the pair of side support blocks;
(v) a pair of tenon blocks (124) provided with through threaded holes (H13) on their top face, the pair of tenon blocks (124) inserted into the slot (S1) of the connecting block (116) such that the pair of tenon blocks (124) are in freely moveable condition in the slot (S1);
(vi) a pair of sliding blocks (118) provided with a step (St1) at top corner, the pair of sliding blocks (118) provided with a slot (S2) on their bottom face, the pair of sliding blocks (118) provided with counter bore holes (H7) on top face of the step (St1) to the slot (S2) of the pair of sliding blocks (118), the pair of sliding blocks (118) provided with a threaded hole (H8) on their back face below the step (St1) perpendicular to the counter bore holes (H7), the pair of sliding blocks (118) adapted to mount on the connecting block (116) in such a way that upper portion of the pair of tenon blocks (124) sits in the slot (S2) of the pair of sliding blocks (118) bringing the counter bore holes (H7) and the through threaded holes (H13) inline to each other and locked in position by means of the plurality of screws (128) passing through the counter bore holes (H7) of the pair of sliding blocks (118) and the through threaded holes (H13) of the pair of tenon blocks (124), the pair of sliding blocks (118) encompasses a pair of dowel bolts (126), adapted to pass through the threaded hole (H8) of the pair of sliding blocks (118);
(vii) a pair of clamping pads (122) provided with holes (H12) therein; and
(viii) a pair of clamps (120) provided with a through hole (H9) at their center, the
pair of clamps (120) provided with counter bore holes (H10) parallel to each other
above the through hole (H9), the pair of clamps (120) provided with a through
threaded hole (H11) below the through hole (H9), the pair of clamps (120) attached
to the pair of clamping pads (122) by means of the plurality of screws (128)
passing through the counter bore holes (H10) of the pair of clamps (120) and the
holes (H12) of the pair of clamping pads (122), the pair of clamps (120) integral
with the pair of clamping pads (122) adapted to pass through the pair of dowel bolts
(126) by means of the through hole (H9) and pushed against a work piece located on
the step (St1) of the pair of sliding blocks (118) by means of tightening a plurality of
nuts (132) over the pair of dowel bolts (126), the pair of clamps (120) integral with
the pair of clamping pads (122) maintained perpendicular to the workpiece by means
of passing of the plurality of bolts (130) through the plurality of nuts (132), the
through threaded hole (H11) of the plurality of clamps (120) and positioning the
plurality of bolts (130) against the pair of sliding blocks (118) by tightening the
plurality of nuts (132).

Typically, the provision of sliding blocks 118 and tenon blocks 124 to lock at different positions on connecting block 116 facilitates in accommodating the workpiece of different heights.

Typically, the provision of clamps 120 integral with clamping pads 122 to lock at different positions on dowel bolts 126 facilitates in accommodating the workpiece of different widths.

Typically, the work pieces are turbine blades.

Typically, the turbine blades are of skewed radial entry T-root blades.

In accordance with the present invention a method of performing pitch milling operation on a compound angle adjustment fixture is provided, said method comprising the steps of:
(i) placing a seesaw block (112) of a compound angle adjustment fixture (100)
between jaws of a vice (134) located on a bed of a CNC machine and locked in position by means of tightening the jaws of the vice (134);
(ii) placing a skewed radial entry T-root blade (136) on a step (St1) of a pair of
sliding blocks (118) at its extreme ends with tapered face (T) of root surface facing upwards and tightly held between a pair of clamping pads (122) and vertical face of the step (St1) of the pair of sliding blocks (118);
(iii) mounting a dial gauge (DG) on a spindle of a CNC machine and a sensor button of the dial gauge (DG) adapted to touch at extreme end on root surface of the skewed radial entry T-root blade (136) along y-axis direction by doing adjustments to the bed of the CNC machine, the sensor button of the dial gauge (DG) in contact with root surface of the skewed radial entry T-root blade (136) adapted to move from one extreme end on root surface of the skewed radial entry T-root blade (136) to other extreme end along y-axis direction by movement of the bed of the CNC machine and deviations and direction of deviations of a pointer of the dial gauge (DG) taken into record;
(iv) performing counter adjustments by trial and error to the seesaw block (112) of the compound angle adjustment fixture (100) based on the deviations and direction of deviations of the pointer of the dial gauge (DG) by tapping the compound angle adjustment fixture (100) up and down using a hammer by opening the jaws of the vice (134) marginally and locking said seesaw block (112) in a position where flatness on root surface of the skewed radial entry T-root blade (136) along y-axis direction is within the tolerance limits of +/- 20 microns by closing the jaws of the vice (134);
(v) touching said sensor button of the dial gauge (DG) at extreme end on root surface
of the skewed radial entry T-root blade (136) along x-axis direction by doing adjustments to the bed of the CNC machine, said sensor button of the dial gauge (DG) in contact with root surface of the skewed radial entry T-root blade (136) adapted to move from one extreme end on root surface of the skewed radial entry T-root blade (136) to other extreme end along x-axis direction by movement of the bed of the CNC machine and deviations and direction of deviations of the pointer of the dial gauge (DG) taken into record; and
(vi) performing counter adjustments by trial and error to a connecting block (116) of
the compound angle adjustment fixture (100) based on the deviations and direction of deviations of the pointer of the dial gauge (DG) by rotating the connecting block (116) clockwise and anti clockwise by loosening a plurality of bolts (130) provided in through threaded hole (H5) of a pair of side support blocks (114) and locking the connecting block (116) in a position where flatness on root surface of the skewed radial entry T-root blade (136) along x-axis direction is within the tolerance limits of +/- 20 microns by tightening the plurality of bolts (130).

BRIEF DESCRIPTION OF THE DRAWINGS:
The invention will now be described with reference to the accompanying drawings in which:
Figures 1(a) and 1(b) illustrates top views of a straight radial entry T-root blade and a skewed radial entry T-root blade respectively according to the prior art;

Figure 2(a) illustrates an isometric view of skewed radial entry T-root blade according to the prior art;

Figure 2(b) illustrates a side view of skewed radial entry T-root blade of figure 2(a);

Figure 3 illustrates an assembled view of skewed radial entry T-root blades according to the prior art;

Figure 4 illustrates an isometric view of skewed radial entry T-root blades assembled on to a disc of a rotor without a closing blade according to the prior art;

Figure 5 illustrates an isometric view of compound angle adjustment fixture in accordance with the present invention;

Figure 6 illustrates an isometric view of base block of figure 5;

Figure 7 illustrates an isometric view of seesaw block of figure 5;

Figure 8 illustrates an isometric view of side support blocks of figure 5;

Figure 9 illustrates an isometric view of connecting block of figure 5;

Figure 10 illustrates an isometric view of sliding blocks of figure 5;

Figure 11 illustrates an isometric view of clamps of figure 5;

Figure 12 illustrates an isometric view of clamping pads of figure 5;

Figure 13 illustrates an isometric view of tenon blocks of figure 5; and

Figure 14 illustrates a perspective view of a compound angle adjustment fixture held tightly between the jaws of a vice located on the bed of a CNC machine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
A preferred embodiment will now be described in detail with reference to accompanying drawings. The preferred embodiment does not limit the scope and ambit of the invention. The description provided is purely by way of example and illustration.

Figure 5 illustrates an isometric view of compound angle adjustment fixture.

In accordance with the present invention, there is provided a compound angle adjustment fixture 100 comprising a base block 110, a seesaw block 112, a pair of side support blocks 114, a connecting block 116, a pair of sliding blocks 118, a pair of clamps 120, a pair of clamping pads 122, a pair of tenon blocks 124 (not shown in the figure), a pair of dowel bolts 126, a plurality of screws 128, a plurality of bolts 130 and a plurality of nuts 132. The screws 128 may include allen screws, while bolts 130 and nuts 132 may include hexagonal, square, or differently shaped bolts and nuts respectively.

Figure 6 illustrates an isometric view of base block of figure 5.
The base block 110 is a rectangular block. A set of four through threaded holes H1, each drilled at each corner are provided on top face of the base block 110. A set of six threaded holes H2 arranged in two rows and three columns are provided on top face at the center of the base block 110.

Figure 7 illustrates an isometric view of seesaw block of figure 5.
The seesaw block 112 is a rectangular block with an arch shaped rounded face at its base.
A set of six threaded holes H3 complementary to the set of six threaded holes H2 of the base block 110 are provided on top face of the seesaw block 112.

Figure 8 illustrates an isometric view of side support blocks of figure 5.
The side support blocks 114 resemble inverted T shape with steps formed on its lateral sides. A through hole H4 is provided at the center of the side support block 114. A gap G1 is provided from top face of side support block 114to the through hole H4 in such a way that the top portion of the side support block 114 is split into two halves. A through threaded hole H5 passing through each of the two halves at top portion of the side support block 114 is drilled. Two holes H6 are drilled on either side on steps provided at base of the side support block 114.

Figure 9 illustrates an isometric view of connecting block of figure 5.
The connecting block 116 is a rectangular block with cylinders C1 attached at either ends. A slot S1 is provided along the connecting block 116 on its top face.

Figure 10 illustrates an isometric view of sliding blocks of figure 5.
The sliding blocks 118 resemble L-shaped blocks. A step St1 is provided at top corner of the sliding blocks 118. A slot S2 is drilled on bottom face of the sliding blocks 118. Two counter bore holes H7 are provided on top face of the step St1 adjoining its vertical face to the slot S2. A threaded hole H8 is drilled perpendicular to the two counter holes H7, below the step St1, on back face of the sliding blocks.

Figure 11 illustrates an isometric view of clamps of figure 5.
The clamps 120 are rectangular blocks. A through hole H9 is provided at the center of the clamps 120. Two counter bore holes H10 parallel to each other are provided on the clamps 120 above the through hole H9. A through threaded hole H11 below the through hole H9 is provided on the clamps 120.

Figure 12 illustrates an isometric view of clamping pads of figure 5.
The clamping pads 122 are rectangular blocks. Two holes H12 are provided on back face of the clamping pads 122.

Figure 13 illustrates an isometric view of tenon blocks of figure 5.
The tenon blocks 124 are rectangular blocks. Two threaded holes H13 complementary to the two counter bore holes H7 are provided on top face of the tenon blocks 124.

The configuration and method of working of compound angle adjustment fixture 100 is as follows:
The seesaw block 112 is placed below the base block 110 and bolted to the base block 110 by means of plurality of screws 128 passing through set of six threaded holes H2 and set of six threaded holes H3. The pair of side support blocks 114 are placed on either side of the base block 110 and locked in position by means of plurality of bolts 130 passing through holes H6 of the pair of side support blocks 114 and set of four through threaded holes H1 of the base block 110. The connecting block 116 is mounted on the pair of side support blocks 114 by means of inserting the cylinders C1 of the connecting block 116 into the through hole H4 of the pair of side support blocks 114. The plurality of bolts 130 inserted into through threaded hole H5 of the pair of side support blocks 114 facilitates in allowing and arresting the rotary movement of the connecting block 116. A pair of tenon blocks 124 is inserted in to the slot S1 of the connecting block 116. The pair of sliding blocks 118 are mounted on the connecting block 116 such that the projecting portion of the pair of tenon blocks 124 is inserted into the slot S2 of the pair of sliding blocks 118 and locked in position by means of plurality of screws 128 passing through two counter bore holes H7 of the pair of sliding blocks 118 and two threaded holes H13 of the pair of tenon blocks 124. A pair of dowel bolts 126 are inserted in to threaded hole H8 of the pair of sliding blocks 118. The pair of clamps 120 attached to the pair of clamping pads 122 by means of plurality of screws 128 passing through two counter bore holes H10 of the pair of clamps 120 and two holes H12 of the pair of clamping pads 122, are adapted to pass through the pair of dowel bolts 126 by means of through hole H9 of the pair of clamps 120 and held in position by means of plurality of nuts 132 passing through the pair of dowel bolts 126. A workpiece is placed in the space provided therein between the pair of sliding blocks 118 and the pair of clamping pads 122 by adjusting the pair of clamps 120 and held tightly in position by means of tightening the plurality of nuts 132 over the pair of dowel bolts 126 such that the plurality of nuts 132 are juxtaposed to the pair of clamps 120. The perpendicularity of the pair of clamps 120 integral with the pair of clamping pads 122 with respect to the work piece is maintained by means of plurality of bolts 130 passing through the plurality of nuts 132, the through threaded hole H11 of the plurality of clamps 120 and positioning the plurality of bolts 130 against the pair of sliding blocks 118 by tightening the plurality of nuts 132.

The primary purpose of pitch milling operation is to achieve a uniform removal of material on blade root surface without disturbing the pre machined compound angle provided on blade root surface. To remove uniform material from root surface of the blade, flatness of root surface of the blade within acceptable tolerance limits of +/- 20 microns on x-y plane is required. The compound angle adjustment fixture 100 facilitates in achievement of flatness on root surface of the blade within acceptable tolerance limits of +/- 20 microns.

Figure 14 illustrates a perspective view of a compound angle adjustment fixture held tightly between the jaws of a vice located on a bed of a CNC machine.
The seesaw block 112 of the compound angle adjustment fixture 100 is placed between the jaws of a vice 134 located on a bed of a CNC machine and locked in position by means of tightening the jaws of the vice 134. The seesaw block 112 of the compound angle adjustment fixture 100 facilitates in up and down movement of the compound angle adjustment fixture 100 by tapping it up and down using a hammer, when the jaws of the vice 134 are in marginally opened condition. A skewed radial entry T-root blade 136 is placed on the step St1 of the pair of sliding blocks 118 with flat face F of the root surface mating with the bottom surface of the step St1 such that tapered face T of the root surface facing upwards and held firmly in position by means of the pair of clamping pads 122 through tightening of the plurality of nuts 132 over the pair of dowel bolts 126 thereby pushing the pair of clamps 120 towards the skewed radial entry T-root blade 136. The plurality of bolts 130 inserted into the through threaded hole H5 of the pair of side support blocks 114 are loosened to facilitate in rotary movement of the skewed radial entry T-root blade 136 to any desired position and locked in that position by tightening the plurality of bolts 130.

A dial gauge DG is attached to the spindle of the CNC machine and the sensor button of the dial gauge DG is adapted to touch at extreme end on root surface of the skewed radial entry T-root blade 136 along y-axis direction by adjusting the bed of the CNC machine. The bed of the CNC machine is moved such that the sensor button of the dial gauge DG moves from one extreme end on root surface of the skewed radial entry T-root blade 136 to other extreme end along y-axis direction and the deviations and direction of deviations of the pointer of the dial gauge DG are recorded. Counter adjustments are done to the compound angle adjustment fixture 100 based on the deviations and direction of deviations of the pointer of the dial gauge DG by trial and error through marginally opening the jaws of a vice and tapping the compound angle adjustment fixture 100 up and down to fix at a position wherein the flatness of the root surface of the skewed radial entry T-root blade is within the tolerance limits of +/- 20 microns along y-axis direction by means of closing the jaws of vice 134.

Now, the sensor button of the dial gauge DG is adapted to touch at extreme end on root surface of the compound angle adjustment fixture 100 along x-axis direction by adjusting the bed of the CNC machine. The bed of the CNC machine is moved such that the sensor button of the dial gauge DG moves from one extreme end on root surface of the skewed radial entry T-root blade 136 to other extreme end along x-axis direction and the deviations and direction of deviations of the pointer of the dial gauge DG are recorded down. Counter adjustments are done to the compound angle adjustment fixture 100 based on the deviations and direction of deviations of the pointer of the dial gauge DG by trial and error by loosening the plurality of bolts 130 provided in the through threaded hole H5 of the pair of side support blocks 114 and rotating the connecting block 116 clockwise and anti-clockwise to fix in a position wherein the flatness of the root surface of the skewed radial entry T-root blade 136 is within the tolerance limits of +/- 20 microns along x-axis direction by means of tightening the plurality of bolts 130 provided in the through threaded hole H5 of the pair of side support blocks 114.

After achieving flatness on compound angle root surface of the skewed radial entry T-root blade 136 on x-y plane within the tolerance limits, a uniform thickness of material can be removed from compound angle root surface using pitch milling operation.

TECHNICAL ADVANCEMENTS:
A compound angle adjustment fixture for pitch milling operation has several technical advantages including but not limited to the realization of :
• a simple compound angle adjustment fixture;
• an easy to use and easy to adjust compound angle adjustment fixture;
• a compound angle adjustment fixture capable of holding the workpiece at any desired compound angle relative to the machining tool;
• a less expensive compound angle adjustment fixture;
• a compound angle adjustment fixture which can accommodate different sizes of workpiece; and
• a compound angle adjustment fixture designed particularly for blades as workpieces.

Although the invention has been described herein above with reference to the embodiments of the invention, the invention is not limited to the embodiments described herein above. It is to be understood that modifications and variations of the embodiments can be made without departing from the spirit and scope of the invention.