Claims:We claim:
1) A fixture (200) for a machining operation comprising a workpiece mounting plate (204) placed at a predefined position on a base plate (202) bolted to a machining table of a boring machine, characterized in that,
a plurality of locators (206) bolted at either ends of the axes of said base plate (202) in such a way that a vertical member (V) of said plurality of locators (206) rests against periphery of said workpiece mounting plate (204);
a plurality of bolts (212) extending from said base plate (202) and said workpiece mounting plate (204) comes in to contact with a bottom face (B1) of a workpiece (216) mounted on said workpiece mounting plate (204) through anticlockwise rotation and thereby achieving a uniform surface at top face (T1) of said workpiece (216) for facing operation by fine tuning of said plurality of bolts (212); and
the plurality of bolts (212) extending from said plurality of locators (206) comes in to contact with an outer surface (O1) of said workpiece (216) held in between therein through clockwise rotation and thereby achieving concentricity of said workpiece (216) with said workpiece mounting plate (204) for boring operation by fine tuning of said plurality of bolts (212).

2) The fixture (200) as claimed in claim 1, wherein a plurality of threaded holes (H10) are provided on said workpiece mounting plate (204) complementary to a plurality of threaded holes (H6) of said base plate (202).

3) The fixture (200) as claimed in claim 1, wherein said plurality of bolts (212) extends from said plurality of threaded holes (H6) of said base plate (202) and said plurality of threaded holes (H10) of said workpiece mounting plate (204).

4) The fixture (200) as claimed in claim 1, wherein a plurality of threaded holes (H12) are provided on a base (B) of said plurality of locators (206) complementary to a plurality of threaded holes (H4) of said base plate (202) for bolting said plurality of locators (206) to said base plate (202).

5) The fixture (200) as claimed in claim 1, wherein one threaded hole (H14) is provided on said vertical member (V) of said plurality of locators (206).

6) The fixture (200) as claimed in claim 1, wherein said plurality of bolts (212) extends from said threaded hole (H14) of said plurality of locators (206).
, Description:FIELD OF THE INVENTION:
[001] The present invention relates to the field of fixtures. Particularly, the present invention relates to a fixture used in boring operations.

BACKGROUND OF THE INVENTION:
[002] Boring is a machining operation involved in increasing the inner diameter of hollow cylindrical objects to achieve precision in hole diameters. Workpieces such as Boilers, Pressure Vessels, Impellers etc., have heavy weight and longer lengths. To perform boring operation on cylindrical workpieces like Impellers, Boilers, Pressure Vessels etc., the cylindrical workpieces needs to be setup on a machining table of a boring machine which in turn calls for the need of a fixture.

[003] Figure 1 illustrates a schematic arrangement of a conventional fixture employed in boring operation.

[004] According to the prior art, a conventional fixture 100 comprises a base plate 102, a workpiece mounting plate 104, a plurality of clamps (not shown in the figure), a plurality of clamping rods (not shown in the figure), a plurality of T-bolts ( not shown in the figure) and a plurality of nuts (not shown in the figure).

[005] The base plate 102 is a circular plate placed on a machining table of a boring machine by inserting it through the plurality of T-bolts provided in the grooves of the machining table of the boring machine and locked in position by means of the plurality of nuts. The base plate 102 is provided with a plurality of holes (not shown in the figure) at a predefined pitch circle diameter.

[006] The workpiece mounting plate 104 is a circular ring provided with a plurality of holes H2 drilled at a predefined pitch circle diameter complementary to the plurality of holes of the base plate 102. The workpiece mounting plate 104 is placed coaxial to the base plate 102.

[007] A cylindrical workpiece of heavy weight is lifted by means of a plurality of ropes extending from a crane and placed over the workpiece mounting plate 104. Due to heavy weight of the cylindrical workpiece, the workmen cannot place the cylindrical workpiece coaxial to the workpiece mounting plate 104 at the first instance. The cylindrical workpiece should be mounted at a uniform height without any tilt otherwise face out happens during facing operation on a boring machine. The cylindrical workpiece also should be mounted concentric to the workpiece mounting plate 104 otherwise run out happens during the boring operation.

[008] To avoid face out and run out during boring operation, the cylindrical workpiece is lifted by placing fulcrums and shims at the bottom of the cylindrical workpiece and hit with the help of hammers on its surface to reach a predefined position. Once, the cylindrical workpiece reaches its predefined position, a plurality of clamping rods are inserted in to the workpiece mounting plate 104 and the base plate 102 and the cylindrical workpiece is clamped to the plurality of clamping rods by means of a plurality of clamps and the plurality of nuts.

[009] The method followed in placing the cylindrical workpiece on the workpiece mounting plate 104 is not fool proof and require skilled workmen. Further, the axial thrust generated during boring operation causes the cylindrical workpiece to move out from the predefined position calling for the resetting of the cylindrical workpiece again.

[0010] Therefore, there is felt a need for development of a fixture for a machining operation to overcome the drawbacks of the prior art and thereby eliminate chances of face out and run out during boring operation

OBJECTS OF THE INVENTION:
[0011] An object of the present invention is to provide a fool proof fixture which eliminates the chances of face out and run out during boring operation.

[0012] Another object of the present invention is to provide a fixture that facilitates the workpiece in withstanding the axial thrust force during boring operation.

[0013] One more object of the present invention is to provide a fixture for easy setup of the workpiece.

[0014] Still another object of the present invention is to provide a fixture to reduce the setup time involved in setting up of the workpiece.

[0015] Further another object of the present invention is to provide a fixture to reduce the cycle time involved in machining the workpiece.

[0016] Yet another object of the present invention is to provide a fixture which helps in precise manufacturing of the workpiece.

[0017] Still one more object of the present invention is to provide a fixture on which the workpiece can be setup by semiskilled operators also.

SUMMARY OF THE INVENTION:
[0018] In accordance with the present invention a fixture for a machining operation is provided, the fixture comprising a workpiece mounting plate placed at a predefined position on a base plate bolted to a machining table of a boring machine, a plurality of locators bolted at either ends of the axes of the base plate and held against the periphery of the workpiece mounting plate and a plurality of bolts extending from the workpiece mounting plate and the plurality of locators towards a workpiece mounted on the workpiece mounting plate to facilitate in achieving a uniform surface at top face of the workpiece and to facilitate in achieving concentricity between the workpiece and the workpiece mounting plate respectively.

BRIEF DESCRIPTION OF THE DRAWINGS:
[0019] The invention will now be described with reference to the accompanying drawings in which:

[0020] Figure 1 illustrates a schematic arrangement of a conventional fixture employed in boring operation according to the prior art;

[0021] Figure 2(a) illustrates a schematic arrangement of a fixture employed in boring operation in accordance with the present invention; and

[0022] Figure 2(b) illustrates a cross-sectional view of a fixture of figure 2(a) with a workpiece mounted on it.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[0023] 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.

[0024] Referring to fig 2(a) and 2(b), In accordance with the present invention, there is provided a fixture 200 comprising a base plate 202, a workpiece mounting plate 204, a plurality of locators 206, a plurality of clamps 208, a plurality of clamping rods 210, a plurality of bolts 212 and a plurality of nuts 214.

[0025] The base plate 202 is a circular plate provided with a plurality of threaded holes H4 equidistantly spaced on either side of the axes. The base plate 202 includes a plurality of holes (not shown in the figure) equidistantly spaced at a predefined pitch circle diameter. The base plate 202 is also provided with a plurality of threaded holes H6 equidistantly spaced at an angle of 90 degrees along the axes.

[0026] The workpiece mounting plate 204 is a circular ring provided with a plurality of holes H8 equidistantly spaced complementary to the plurality of holes of the base plate 202 at the said predefined pitch circle diameter. The workpiece mounting plate 204 is also provided with a plurality of threaded holes H10 equidistantly spaced at an angle of 90 degrees along the axes complementary to the plurality of threaded holes H6 of the base plate 202.

[0027] The plurality of locators 206 are typically of L-shaped cross-section. The plurality of locators 206 are provided with a plurality of threaded holes H12 on their base B spaced complementary to the plurality of threaded holes H4 of the base plate 202 as shown in the figure 2(b). The plurality of locators 206 are also drilled with one threaded hole H14 on their right angled vertical member V as shown in the figure 2(b).

[0028] The configuration and the method of working of the fixture 200 is explained in detail with reference to the figures 2(a) and 2(b) as follows:

[0029] The workpiece mounting plate 204 is placed on the base plate 202 such that the plurality of holes (H8 and H10) of the workpiece mounting plate 204 are inline to the plurality of holes (not shown in the figure and H6) of the base plate. The plurality of bolts 212 are adapted to pass through the plurality of threaded holes H6 of the base plate 202 and the plurality of threaded holes H10 of the workpiece mounting plate 204 inline to each other. The base plate 202 mounted with the workpiece mounting plate 204 is bolted to a machining table of a boring machine by means of a plurality of T-bolts (not shown in the figure) extending through a plurality of grooves of the machining table of the boring machine. The plurality of locators 206 are mounted along the axes of the base plate 202 and bolted by means of a plurality of bolts 212 passing through the plurality of threaded holes H12 of the plurality of locators 206 and the plurality of threaded holes H4 of the base plate 202 such that the right angled vertical member V of the plurality of locators 206 rests against the workpiece mounting plate 204. A workpiece 216 held by the ropes extending from a crane is adapted to mount on the workpiece mounting plate 204 with the help of workmen in such a way that a bottom face B1 of the workpiece 216 rests over the plurality of bolts 212 projecting out at right angles along the axes of the workpiece mounting plate 204 and an outer surface O1 of the workpiece 216 is held between the plurality of locators 206.

[0030] Now, the operator need to do the setting of the workpiece 216 to prevent face out and run out. Firstly, the adjustment of the workpiece 216 is done based on the readings of the height gauge from the top face T1 of the workpiece 216, through anticlockwise rotation of the plurality of bolts 212 extending from the workpiece mounting plate 204 such that uniform height is achieved on the top face T1 of the workpiece 216 and thereby eliminating face out during facing operation on the boring machine. Lastly, the workpiece 216 is made concentric with workpiece mounting plate 204 based on the readings of the dial gauge, through adjustments done by clockwise rotation of the plurality of bolts 212 extending from the plurality of locators 206 and thereby eliminating run out during boring operation.

[0031] Once, the precise setting position is reached, the plurality of clamping rods 210 are inserted into the plurality of holes H8 of the workpiece mounting plate 204 and the plurality of holes of the base plate 202 and locked in position by means of the plurality of clamps 208 and the plurality of nuts 214. Finally, all the plurality of bolts 212 are kept in engaged position with the workpiece 216 and thereby arresting its degrees of freedom.

[0032] Typically, the plurality of locators 206 facilitates in mounting of the workpiece 216 at near to precise setting position.

[0033] Typically, the plurality of locators 206 facilitates in withstanding the axial thrust force of the workpiece 216 during boring operation.

TECHNICAL ADVANCEMENTS:
[0034] A fixture for a machining operation has several technical advantages including but not limited to the realization of:
• a fool proof fixture which eliminates the chances of face out and run out during boring operation;
• a fixture that facilitates the workpiece in withstanding the axial thrust force during boring operation;
• a fixture for easy setup of the workpiece on a boring machine;
• a fixture to reduce the setup time involved in setting up of the workpiece;
• a fixture to reduce the cycle time involved in machining the workpiece;
• a fixture which helps in precise manufacturing of the workpiece; and
• a fixture on which the workpiece can be setup by semiskilled operators also.

[0035] 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.