FIELD OF INVENTION
The present invention relates to an improved Master Former device for machining external fillet of cylindrical profiled bar type steam turbine blade on 2 Axis conventional machines by copy milling process.
BACK GROUND OF INVENTION
External Fillet Milling operation is being done in turbine blade manufacturing for making expansion angle on suction side of the profile of blades.
As per prior art, external fillet milling of T2 profile bar type blade was being carried out by copy milling process using old designed MASTER FORMER.
Expansion angle on suction side of the profile was not coming as per requirement using old designed MASTER FORMER due to design restriction. Further manual grinding was done to get required expansion angle.
Expansion angle is the angle between steam inlet and steam exit of the profile and varies from 0°-22° as it varies from blade to blade.
In this process, blade was getting rejected and quality of blade was also poor.
It was necessary to develop a new design MASTER FORMER to carry out external fillet milling of T2 blades on 2-axis conventional machines by copy milling process.

To improve quality and reduce rejection of T2 blades during grinding and polishing was another criteria behind this invention. After this invention, chances of rejection during polishing is considerably reduced because expansion angle on suction side of the profile is being made on the machine itself as per requirement, no manual grinding is being done to get the required expansion angle.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose an improved master former device for machining external fillet of cylindrical profiled bar type steam turbine blade on 2 Axis conventional machines by copy milling process, which is capable of producing required expansion angle on suction side of the profile of turbine blades.
Another object of the invention is to propose an improved master former device for machining external fillet of cylindrical profiled bar type steam turbine blade on 2 Axis conventional machines by copy milling process, which is able to avoid manual grinding to obtain the required expansion angle and to reduce chances of rejection during polishing.
Further object of the invention is to propose an improved master former device for machining external fillet of cylindrical profiled bar type steam turbine blade on 2 Axis conventional machines by copy milling process, which is able to

improve quality of milling of external fillet of profile bar type steam turbine blades.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1 - Shows an isometric view of the invented master former device.
Fig.2 - Shows the elevation of the invented master former device.
Fig.3 - Shows the isometric view of the invented master Former device.
Fig.4 - Shows the invented master Former device.
Fig.5 - Shows the old master former device.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
A new MASTER FORMER has been developed to take care and to overcome the inherent problems of external fillet milling of cylindrical profiled T2 blade on 2-axis conventional machine by copy milling process.
The new MASTER FORMER has got the ability to provide the required expansion angle on suction side of the blade during external fillet milling on 2-axis.
Fig.l shows the improved master Former device (D). The device (D) is made of alloy steel material EN-24/EN 36 which is carburized and hardened. Surfaces SI,

S2, S3 shown in the drawing are hardened to Rockwell 58-62 after carburization to guard against the wearing of the surface and profile on which the stylus or tracer unit of the machine moves to produce the required blade of the turbine. The device is having a total length of 120mm, a height of 43 mm, a width of 40 mm and a profile at the middle, the replica of which is to be provided on the turbine blade. The machine is equipped with Tracer Unit when the master Former device is fixed on the machine. Tracer moves on master former copying the shape of it and giving direction to the cutter for cutting accordingly on the blade. Existing master Former is shown in Fig.5. This master was producing poor quality of fillet. After a thorough study and root cause analysis, design of master former was found to be responsible for producing poor quality fillet. On the base of the above study a new master Former device is made and used on the machine which produces perfect external fillet and consequently correct expansion angle. The new master with important dimension is shown in fig.l and fig.3.

WE CLAIM
1. An improved master former device for machining external fillet of cylindrical
profiled bar type steam turbine blade on 2 Axis conventional machines by
copy milling process, the said master former device (D) comprising;
an alloy steel block having a profile at the middle for producing the same profile on the blade for providing required expansion angle, the said block being made having total length 120 mm, width 40 mm, height 43 mm wherein the thickness 'T' is made of 5 mm for required external fillet milling for achieving correct expansion angle within 0°-22° in the turbine blades.
2. The improved master former device as claimed in claim 1, wherein the said
device is carburized and hardened to RE 58-62.