Claims:We claim:
1) A fixture (200) to facilitate in slot milling operation on an unfinished locknut (100), said fixture (200) comprising:
a) a headed bolt (20) comprising an integrally formed head at its one end and threads (T1) over its circumference complementary to threads of the unfinished locknut (100), said head of the headed bolt (20) provided with a flat surface (F) on its top and bottom adapted to held between jaws of a machining center, said headed bolt (20) provided with a hole (H1) at its other end perpendicular to its threaded surface; and
b) a stopper plate (22) with a hole, placed against said unfinished locknut (100) encompassing said headed bolt (20) in such a way that said hole of the stopper plate (22) and said hole (H1) of the headed bolt (20) are concentric to each other and locked in position by means of a fastener (24).

2) A fixture (200) to facilitate in slot milling operation on an unfinished locknut (100) as claimed in claim 1, wherein said fastener (24) can be plain or threaded.

3) A fixture (200) to facilitate in slot milling operation on an unfinished locknut (100) as claimed in claim 1, wherein said hole (H1) of the headed bolt (20) can be plain or threaded.

4) A method to facilitate in slot milling operation on an unfinished locknut (100) by using a fixture (200), said method comprising the steps of :
a) turning, drilling and boring on a cylindrical bar stock held in between jaws of a turning center at a predetermined position;
b) parting off said unfinished locknut (100) from the cylindrical bar stock followed by a threading operation on its inner diameter;
c) holding of a headed bolt (20) of said fixture (200) in between jaws of a machining center and said unfinished locknut (100) adapted to pass over its circumference;
d) arresting further movement of said unfinished locknut (100) by placing a stopper plate (22) of said fixture (200) adjacent to said unfinished locknut (100) in such a way that a hole of said stopper plate (22) and a hole (H1) of said headed bolt (20) are concentric to each other and locked in position by means of a fastener (24); and
e) performing slot milling operation over circumference of said unfinished locknut (100) in a fool proof environment.

5) A method to facilitate in slot milling operation on an unfinished locknut (100) by using a fixture (200) as claimed in claim 4, wherein said predetermined position is decided depending on the space required to accommodate a tool in parting off operation.

6) A method to facilitate in slot milling operation on an unfinished locknut (100) by using a fixture (200) as claimed in claim 4, wherein a greater number of locknuts can be produced from a given raw material.

7) A method to facilitate in slot milling operation on an unfinished locknut (100) by using a fixture (200) as claimed in claim 4, wherein setup of each of said unfinished locknut every time for slot milling operation can be eliminated if once said headed bolt (20) of said fixture (200) is setup for first time.

8) A method to facilitate in slot milling operation on an unfinished locknut (100) by using a fixture (200) as claimed in claim 4, wherein variation in locknuts produced after slot milling operation is eliminated.

9) A method to facilitate in slot milling operation on an unfinished locknut (100) by using a fixture (200) as claimed in claim 4, wherein said slot milling operation over circumference of said unfinished locknut (100) facilitates in carrying out deformation operation.

10) A method to facilitate in slot milling operation on an unfinished locknut (100) by using a fixture (200) as claimed in claim 4, wherein said slot milling operation over circumference of said unfinished locknut (100) facilitates a spanner in gripping while tightening of a locknut over a bolt.
, Description:FIELD OF THE INVENTION:
The present invention relates to a fixture for holding an unfinished locknut during slot milling operation. Particularly, the present invention relates to a fool proof mechanism for holding the unfinished locknut firmly while slot milling operation.

BACKGROUND OF THE INVENTION:
Generally, locknuts find their application in connecting two objects. In turbine industry, a plurality of specifically designed locknuts is used to connect a steam turbine to an alternator through an industrial gear box. Locknuts are designed in such a way that they withstand high vibrations from the steam turbine during operation. To eliminate the chances of loosening of the locknut after mating with a bolt through complementary threads, a deformation operation is performed by holding the locknut with a tool at three different points equidistantly spaced at 120 degrees angle around its circumference. To facilitate in carrying out the deformation operation, a plurality of slots are supposed to be machined around the circumference of the locknut in advance.

Figure 1 illustrates a perspective view of a cylindrical bar stock.

Figures 2(a) and 2(b) illustrates an isometric view and cross sectional view of final locknut respectively after performing all operations.

The cylindrical bar stocks are of generally 1m length. As per the design requirement, the length of the locknut should be 29.5mm and is generally indicated by a reference numeral L1 as shown in the figure 2(b). The slot milling operation should be done across the length of 18.5mm over the circumference of the locknut to create a plurality of serrations and is generally indicated by a reference numeral L2 as shown in the figure 2(b).

The conventional method of manufacturing locknuts involves a plurality of operations to be carried out in sequence as follows:
1) Turning, drilling & boring of a bar stock.
2) Parting off unfinished locknut from the bar stock followed by step milling operation on top surface and bottom surface of the unfinished locknut to provide proper butting surface to the jaws of a machining center.
3) Slot milling operation on the locknut to provide serrations over its circumference.
4) Facing off extra material from the locknut followed by threading on its inner surface.

Figure 3 illustrates a cross sectional view of a cylindrical bar stock held between the jaws of a CNC turning center after turning, drilling and boring operation in accordance with the conventional method.
The cylindrical bar stock is fed in to the jaws of the CNC turning center in such a way that an additional stock of 13mm is left behind intentionally than the design requirement length L1 of the locknut and is generally indicated by a reference numeral L3. Out of 13mm additional stock (L3), 3mm stock generally indicated by a reference numeral L4 is used to accommodate the tool in parting off operation and 10mm stock generally indicated by a reference numeral L5 is used to facilitate in holding of the unfinished locknut during slotting of serrations over its circumference.

Figure 4(a) illustrates a cross sectional view of parted off and step milled unfinished locknut in accordance with the conventional method.

Figures 4(b) and 4(c) illustrate a right side view and sectional view at portion A-A of the figure 4(a) respectively.

After turning, drilling and boring operation, the unfinished locknut is parted off from cylindrical bar stock followed by a step milling operation at top surface and bottom surface on its extra 10mm stock to provide proper butting surface for the jaws of the machining center in the next slot milling operation. The step milling operation on top surface and bottom surface of the unfinished locknut should be done precisely in order to maintain symmetry from imaginary center and to achieve concentricity with chuck while setting up for next slot milling operation.
Figures 5(a) and 5(b) illustrate a cross sectional view and right side view of an unfinished locknut held between the jaws of a machining center during slot milling operation respectively in accordance with the conventional method.

Figure 5(c) and 5(d) illustrates a front view and right side view of an unfinished locknut respectively after slot milling operation.

The step milled portions on top surface and bottom surface of the unfinished locknut are adapted to firmly butt against the jaws of the machining center as shown in the figure 5(a) and slot milling operation is performed over the circumference of the locknut as shown in the figure 5(c).

Figure 6 illustrates a cross sectional view of a finished locknut held between the jaws of a turning center after facing and threading operation in accordance with the conventional method.

The extra 10mm stock used to hold the unfinished locknut firmly during slot milling operation is faced off thereby achieving the design requirement length of the locknut followed by threading operation on inner diameter of the unfinished locknut.

By considering 1m length of cylindrical bar stock, we can produce a total of 23 locknuts approximately of design requirement length (L1) with conventional method.
Total number of locknuts = 1000mm
39.5(10mm for holding during slot milling)+ 3(Parting off)

As mentioned above, 13mm stock (L3) is being wasted in conventional method of locknuts manufacturing. Moreover, the setup time required for setting up of each unfinished locknut to perform slot milling operation is very high and requires dexterity of the operator. Further, as each unfinished locknut is supposed to be setup individually for slot milling operation, the variation in finished locknuts is very high.

Therefore, there is felt a need for development of a fixture for holding unfinished locknuts during slot milling operation to overcome the drawbacks of the prior art and thereby providing a fool proof mechanism.

OBJECTS OF THE INVENTION:
An object of the present invention is to provide a simple and fool proof mechanism for holding unfinished locknut during slot milling operation.

Another object of the present invention is to reduce wastage in raw material and produce greater number of locknuts from given raw material.

One more object of the present invention is to reduce time involved in setting up of each unfinished locknut for slot milling operation.

Still another object of the present invention is to reduce effort and dexterity of the operator in setting up of each unfinished locknut for slot milling operation.

Further another object of the present invention is to eliminate variation in locknuts produced after slot milling operation.

SUMMARY OF THE INVENTION:
In accordance with the present invention a fixture (200) to facilitate in slot milling operation on an unfinished locknut (100) is provided, said fixture (200) comprising:
i) a headed bolt (20) comprising an integrally formed head at its one end and threads (T1) over its circumference complementary to threads of the unfinished locknut (100), the head of the headed bolt (20) provided with a flat surface (F) on its top and bottom adapted to held between jaws of a machining center, the headed bolt (20) provided with a hole (H1) at its other end perpendicular to its threaded surface; and
ii) a stopper plate (22) with a hole, placed against the unfinished locknut (100) encompassing the headed bolt (20) in such a way that the hole of the stopper plate (22) and the hole (H1) of the headed bolt (20) are concentric to each other and locked in position by means of a fastener (24).

Typically, the fastener (24) can be plain or threaded.

Typically, the hole (H1) of the headed bolt (20) can be plain or threaded.

In accordance with the present invention a method to facilitate in slot milling operation on an unfinished locknut (100) by using a fixture (200) is provided, said method comprising the steps of:
i) turning, drilling and boring on a cylindrical bar stock held in between jaws of a turning center at a predetermined position;
ii) parting off the unfinished locknut (100) from the cylindrical bar stock followed by a threading operation on its inner diameter;
iii) holding of a headed bolt (20) of the fixture (200) in between jaws of a machining center and the unfinished locknut (100) adapted to pass over its circumference;
iv) arresting further movement of the unfinished locknut (100) by placing a stopper plate (22) of the fixture (200) adjacent to the unfinished locknut (100) in such a way that a hole of the stopper plate (22) and a hole (H1) of the headed bolt (20) are concentric to each other and locked in position by means of a fastener (24); and
v) performing slot milling operation over circumference of the unfinished locknut (100) in a fool proof environment.

Typically, the slot milling operation over circumference of the unfinished locknut (100) also facilitates a spanner in gripping while tightening of a locknut over a bolt apart from carrying out deformation operation.

BRIEF DESCRIPTION OF THE DRAWINGS:
The invention will now be described with reference to the accompanying drawings in which:
Figure 1 illustrates a perspective view of a cylindrical bar stock;

Figures 2(a) and 2(b) illustrates an isometric view and cross sectional view of final locknut respectively after performing all operations;

Figure 3 illustrates a cross sectional view of a cylindrical bar stock held between the jaws of a CNC turning center after turning, drilling and boring operation according to the prior art;

Figure 4(a) illustrates a cross sectional view of parted off and step milled unfinished locknut according to the prior art;

Figures 4(b) and 4(c) illustrate a right side view and sectional view at portion A-A of the figure 4(a) respectively;

Figures 5(a) and 5(b) illustrate a cross sectional view and right side view of an unfinished locknut held between the jaws of a machining center during slot milling operation respectively according to the prior art;

Figure 5(c) and 5(d) illustrates a front view and right side view of an unfinished locknut respectively after slot milling operation according to the prior art;

Figure 6 illustrates a cross sectional view of a finished locknut held between the jaws of a turning center after facing and threading operation according to the prior art;

Figure 7 illustrates a cross sectional view of a cylindrical bar stock held between the jaws of a CNC turning center after turning, drilling and boring operation in accordance with the present invention;

Figure 8 illustrates a cross sectional view of a parted off unfinished locknut held between the jaws of a turning center after threading operation in accordance with the present invention;

Figure 9(a) illustrates a front view of a fixture held between the jaws of a machining center with a cross sectional view of an unfinished locknut coupled over it in accordance with the present invention; and

Figures 9(b) and 9(c) illustrates a front view and right side view of a headed bolt of figure 9(a) respectively in accordance with the present invention.
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 7 illustrates a cross sectional view of a cylindrical bar stock held between the jaws of a CNC turning center after turning, drilling and boring operation.

In accordance with the present invention, firstly, the cylindrical bar stock is fed in to the jaws of a CNC turning center in such a way that only 3mm of additional stock (L4) is left behind intentionally than the design requirement length (L1) of the locknut. The 3mm additional stock (L4) is used to accommodate the tool in parting off operation after turning, drilling and boring operation is carried out on the cylindrical bar stock.

Figure 8 illustrates a cross sectional view of a parted off unfinished locknut held between the jaws of a turning center after threading operation.

In accordance with the present invention, secondly, the parted off unfinished locknut 100 is held between the jaws of a turning center to carry out threading operation on its inner diameter as shown in the figure 8.

Figure 9(a) illustrates a front view of a fixture held between the jaws of a machining center with a cross sectional view of an unfinished locknut coupled over it.

Figures 9(b) and 9(c) illustrates a front view and right side view of a headed bolt of figure 9(a) respectively.

In accordance with the present invention, there is provided a fixture 200 comprising a headed bolt 20, a stopper plate 22 and a fastener 24.

The headed bolt 20 is provided with threads T1 over its circumference complementary to the threads of the unfinished locknut 100 as shown in the figure 9(b). The head of the headed bolt 20 is provided with flat surface F on its top and bottom. The headed bolt 20 is provided with a hole H1 on its extreme end perpendicular to its threaded surface.

The stopper plate 22 is provided with a hole complementary to the hole H1 of the headed bolt 20.

The hole H1 of the headed bolt 20 can be plain or threaded.

The fastener 24 can be plain or threaded.

The configuration and method of working of the fixture 200 in accordance with the present invention is as follows:
The headed bolt 20 is held between the jaws of a machining center in such a way that flat surface F at the top and bottom of the headed bolt 20 mates with the jaws of the machining center. Lastly, the unfinished locknut 100 is adapted to pass over the threads T1 of the headed bolt 20 and locked in position to carry out slot milling operation. The chances of forward movement of the unfinished locknut 100 during slot milling operation is eliminated by placing a stopper plate 22 adjacent to the unfinished locknut 100 such that the hole of the stopper plate 22 and the hole H1 of the headed bolt 20 are concentric to each other and locked in position by means of a fastener 24 as shown in the figure 9(a).

The present method of manufacturing locknuts doesn’t require each unfinished locknut 100 to be setup individually for slot milling operation if once the fixture 200 is setup for the first time. Further, the present method produces a total of 30 locknuts approximately of design requirement length (L1) for a given 1m length of cylindrical bar stock.

TECHNICAL ADVANCEMENTS:
A fixture to facilitate in slot milling operation on an unfinished locknut has several technical advantages including but not limited to the realization of :
• a simple and fool proof mechanism for holding unfinished locknut during slot milling operation;
• a fixture which helps in reducing the wastage of raw material and thereby producing a greater number of locknuts from given raw material;
• a fixture which helps in reducing the time involved in setting up of each unfinished locknut for slot milling operation;
• a fixture which helps in reducing effort and dexterity of the operator in setting up of each unfinished locknut for slot milling operation; and
• a fixture which facilitates in eliminating variation in locknuts produced after slot milling operation.

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.