CLIAMS:We claim:
1. A drill for improved hole drilling comprising a taper shank, a neck, helical flutes and a point characterized by
three point angles in said drill.
2. The drill as claimed in claim 1, wherein first point angle measures 1180.
3. The drill as claimed in claim 1, wherein second point angle measures in the range 700-720.
4. The drill as claimed in claim 1, wherein third point angle measures in the range 540-560.
5. The drill as claimed in claim 3, wherein said second point angle measures 720.
6. The drill as claimed in claim 4, wherein said third point angle measures 540.
7. The drill as claimed in claims 1 and 5, wherein said second point angle is ground over a length of lip ranging, C1=1.5 to 5 mm.
8. The drill as claimed in claim 7, wherein said second point angle is ground over a length of lip, C1=1.7 mm.
9. The drill as claimed in claims 1 and 6, wherein said third point angle is ground over a length of lip ranging, C2=0.5 to 2.0 mm.
10. The drill as claimed in claim 9, wherein said third point angle is ground over a length of lip, C2=0.7 mm.
11. The drill as claimed in claim 1, wherein drill diameter varies from 10 to 25 mm.
12. The drill as claimed in claim 11, wherein said drill diameter is 11.5 mm.
13. The drill as claimed in any one of preceding claims, wherein material used for drilling is steel and cast iron. ,TagSPECI:TECHNICAL FIELD
The present subject matter described herein generally relates to a drilling machine with an improved drill point design and more particularly, to a triple point angled drill having such geometry and construction that improves the hole quality in terms of dimensions and shape with simultaneous enhancement in productivity.

BACKGROUND
Drilling is one of the most commonly used and basic machining process in various industries such as automotive, aircraft and aerospace, dies/molds, home appliance, medical and electronic equipment industries. Due to the increasing competitiveness in the market, performance of the drilling processes must be increased to remain competitive. Moreover, tight geometric tolerance requirements in designs demand that drilled hole precision must be increased in production. The point geometry of the twist drill is the key element in determining two important drill performance characteristics, namely, the upward thrust along the drill axis and the drilling torque (Yang et al., 2002). A minimization of both these quantities lead to an improvement in performance by reducing drill deflection due to thrust loading, by lowering the power required for the drilling operation and by improving drill life. Even though the conical flank profile configuration is the most commonly used drill point geometry, and is the easiest to grind, it does not provide the most efficient cutting action in this regard (Batzer et al., 2001). To overcome this, a number of different point shapes have been developed to provide inherent favorable characteristics; such as the helical drill with an S-shaped chisel edge that provides a self-centering action and the Racon drill that provides a reduction in exit burr formation (Wang et al., 2001). However, these geometries have tended to evolve from experience employing extensive experiments to evaluate and modify the design and are not optimal with respect to thrust and torque reduction.
A typical drill has several design parameters such as tip angle, chisel edge angle, chisel edge length, cutting lip length and helix angle. Various elements of conventional drill are shown in Figure 1. Some terms in the figure are self evident and for some terms, symbols have been used. For example, 2ⱷ is the point angle, ῳ is the helix angle and ᶲ is the chisel edge angle of the drill. Each one of these parameters affects the cutting forces and drilled hole qualities in various ways. It is known that a drill consists of two main cutting parameters, namely; the chisel edge and the cutting lips. The chisel edge extrudes into the work piece material and contributes substantially to the thrust force. The cutting lips cut out the material and produce the majority of the drilling torque and thrust. During a drilling operation, the chips are formed along the cutting lip and moved up following the drill helix angle. The drill geometry has a complicated effect on the cutting forces. In addition to that, the cutting forces depend on the tool and work piece material properties and machining conditions. The cutting forces are the main reason of the problems related to drilling in manufacturing such as form and surface errors, vibration, tool wear etc.
In conventional drill, single point angle is provided whose value (2ⱷⱷ) varies from 118o to 140o. Double point angled drills as shown in Figure 2 are also known. In such type of drills, the second point angle is 2ⱷo=70o and it is ground over a length of lip, C= 2.5 to 15 mm (Figure 2). This point increases tool life or for the same life, enables the cutting speed to be increased (Arshinov and Alekseev, 1976).
Like single point tools, drill also possesses rake and relief angles. The rake angle (γ) is the angle between the tangent to the face at the point of lip (cutting edge) being referred to and the normal, at the same point, to the surface of revolution described by the lip about the drill axis. The rake angle (γ) is measured in a plane perpendicular to the lip (Plane B-B in Figure 3).
Relief angle (α) is the angle between a tangent to a flank, or lip relief surface, at the point being considered on the lip and a tangent at the same point to the circle the point describes as it rotates about the drill axis. The angle is measured in A-A plane (Figure 3) which is tangent to the cylindrical surface on which the above mentioned point on the lip lies. The axis of the cylindrical surface coincides with the drill axis (Figure 3). Sometimes, instead of single relief angles, two relief angles, known as primary and secondary relief angles, are provided to enhance the tool life of drill as shown in Figure 5. Combination of relief angle and wedge angle is known as cutting angle.
US 588036 have recommended the use of tip angle of 118o to 140o, the second cutting angle of 20o and third cutting angle of 30o.
It has been found theoretically and practically that in spite of availability of conventional and double point angled drills, some problems and disadvantages exists in drilling operations such as:
• Inaccurate dimensions of drilled hole;
• Incorrect shape of drilled hole; and
• Less production
In view of foregoing, there is an utmost desire for a better drill design which can overcome problems present in existing designs and help deliver better results. Therefore, the present subject matter provides an improved design of a drill point geometry and construction that helps improve the hole quality in terms of dimensions and shape; and simultaneously enhancing the productivity.

SUMMARY
It is a primary object of the present subject matter to provide three point angles in a single drill in order to overcome problems and disadvantages in state-of-the-art drill designs.
It is another object of the present subject matter to improve the quality of a drilled hole in terms of its size.
It is yet another object of the present subject matter to improve the quality of a drilled hole in terms of its shape by reducing its ovality.
It is still another object of the present subject matter to enhance productivity by increasing tool life.
It has been found by way of rigorous experiments that the invented tool as proposed in the present subject matter has a capability of improving drilling accuracy and productivity. The present subject matter produces better quality holes than the ordinary drills known in state-of-the-art. The drilling tests have been performed for different work pieces in which the accuracy of machined holes, surface roughness and productivity has been experimentally measured.
The three types of drills i.e., conventional drill of single angle of 1180, double angled drill consisting one angle of 1180 and second angle around 700-720 and triple angled drill consisting of first angle of 1180, second angle around 700-720 and third angle around 540 - 560 have been used for the purposes of experiment. It has been found that triple point drill has better hole quality in terms of dimensions and shape, along with the improvement of the productivity. It has been found that close tolerances may be achieved in the hole size with the use of this invented tool.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The foregoing and further objects, features and advantages of the present subject matter will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings, wherein like numerals and/or symbols are used to represent like elements and/or angles and wherein:
Figure 1 represents different elements of a conventional drill.
Figure 2 represents two point angles in a double point angled drill, wherein the first point angle is 2ⱷ and second point angle is 2ⱷ0; and second point angle is ground over a length of lip, C= 1.7 mm and ῳ is helix angle of the flute.
Figure 3 represents rake angle γ and relief angle α of a drill in plane B-B and plane A-A respectively.
Figure 4 represents three point angles in a triple point angled drill, wherein the first point angle is 2ⱷ, second point angle is 2ⱷ0 and third point angle is 2 ⱷ 1; and second point angle is ground over a length of lip, C1= 1.7 mm and third point angle is ground over a length of lip, C2= 0.7 mm.
Figure 5a represents single point angle ϴP and Figure 5b represents primary relief angle ϴ2 and secondary relief angle ϴ 3 respectively in the direction of arrow IV of Figure 5a.
Figures 6(a) to 6(c) represents different views of experimental set up (the drilling machine along with the specially designed jig and drill) utilized for machining the component.
Figure 7 represents machined component with measurements of drilled holes, wherein material of the component is mild steel.
Figure 8 represents different angles of a single point tool (turning tool); the nomenclature is as under:
α = Side Relief Angle
β = Wedge Angle
γ = Side Rake Angle
δ = Cutting Angle
ⱷ = Plan Approach Angle
ⱷ 1 = End Cutting Edge Angle
ἐ= Nose Angle
α 1 = End Relief Angle
γ 1 = End (or Back) Rake Angle

DETAILED DESCRIPTION OF THE INVENTION
The embodiments of the present subject matter are described in detail with reference to the accompanying drawings. However, the present subject matter is not limited to these embodiments which are only provided to explain more clearly the present subject matter to the ordinarily skilled in the art of the present disclosure. In the accompanying drawings, like reference numerals and/or symbols are used to indicate like elements and/or angles.

The different views of a drilling machine with specially designed jigs for the component being manufactured is shown in Figures 6 (a) to 6 (c) respectively and is utilized for performing the experiments. The table is the base of the drilling machine and is the surface used to keep the vice in its place. Most of the times, the table is swiveled out of the way to make it easier to drill holes in work pieces that are oddly shaped and height of the table is adjusted with a crank and locked in place and a column is used to support the table. The vice is a device such as a clamp used to hold the material that is being drilled firmly in place; the vice has two jaws that may be brought together or separated by a lever. The drill chuck and spindle holds the drilling tools such as a drill bit, which is tool used to create cylindrical holes. The chuck is raised and lowered using the feed lever and the chucks are available in different sizes which depend on the diameter of the largest drill bits that can be used. The spindle holds the drill chuck, which holds the cutting tools such as drill bits and center drills. The handle of drill machine is used to raise and lower the drill bit so that holes can be cut accurately. The jig is used to guide the drill for making holes at the required position accurately. The work piece is placed below the jig and drilling operation is carried out.
The three types of drills i.e., conventional drill of single angle of 1180, double angled drill consisting one angle of 1180 and second angle of 720 and triple angled drill consisting of first angle of 1180, second angle of 720 and third angle of 540 are used for performing drilling operations and the component being manufactured is shown in Figure 7. Proposed specifications of point geometry of three types of drills used are shown in Table 1.
Different experiments to evaluate the performance of the proposed drill designs have been performed on a typical drilling machine as shown in Figures 6 (a) to 6 (c). However, the drills were ground at a special tool and cutter grinding machine, the different drill designs were tested by varying the lip angles and length of the profile. The best results are achieved for the triple angled drill as shown in Figure 4. First of all, the ordinary drill of lip angle 1180 is tested experimentally (case 1) on the work pieces of steel and cast iron; the results of which are shown in Table 2. The similar experiments are performed for double angled drill on the same machine and same work piece and second point angle of the double angled drill is varied along with the variation in the length of the angled profile to reach at the final drill design as stated in case 2; the results of which are shown in Table 3.
Similarly, the triple point angled drill (case 3) is tested experimentally on the stated conditions and it is found that the triple point drill has better hole quality and tight tolerances, as compared to the results of ordinary and double point angled drill and as highly desired in the designs along with the improvement of the productivity as stated in Table 4.
Table 1: Proposed drill designs specifications
Parameter Normal drill (Case 1) Double angled drill (Case 2) Triple angled drill (Case 3)
First angle, diameter and length of profile Angle 1180 on full profile Angle 1180 up to ⱷ8.60 Angle 1180 up to ⱷ 7.60 mm
Second angle, diameter and length of profile Not applicable Angle 720 and diameter from ⱷ 8.60mm to ⱷ 11.5mm and length around 2mm Angle 720 and diameter from ⱷ 7.51mm to ⱷ 10.48mm and length around 2 mm
Third angle, diameter and length of profile Not applicable Not applicable Angle 540 and diameter from ⱷ 10.48 mm to ⱷ 11.5 mm and length around 1 mm

Table 2: Results for ordinary drill of lip angle 1180 (Case 1)
S.N Work material No. of drilled hole before regrinding No. of drilled hole after regrinding Surface finish
1. Steel 640 420 average
2. Cast Iron 660 430 average

Table 3: Results for Double profile drill of lip angles 1180 and 720 (Case 2)
S.N. Work material No. of drilled hole before regrinding No. of drilled hole after regrinding Surface finish
1. Steel 680 432 good
2. Cast Iron 690 446 good

Table 4: Results for Triple profile drill of lip angles 1180, 720 and 540 (Case 3)
S.N. Work material No. of drilled hole before regrinding No. of drilled hole after regrinding Surface finish
1. Steel 695 480 Very good
2. Cast Iron 710 512 Very good

The present subject matter as described above provides improved drill point geometry i.e., the triple point angled drill which has better performance over other types of drills.
The present subject matter also offers remarkable improvements in terms of quality of holes produced as well as productivity enhancement. There is productivity enhancement of about 14% to 20% in steel components and 18% to 25% in cast iron components in terms of number of holes produced.
The experiments conducted further shows that instead of fixed value of 700 of second point angle as suggested by Arshinov and Alekseev (1976) in case of double point angled drill; better results are achieved upto 720.
The present subject matter further shows that third point angle is varied from 540 to 560 with better results.
The present subject matter has been experimented for drill diameters ranging from 10 to 25 mm and results obtained with drill diameter 11.5 mm are shown in the table. The present experiments are performed for cast iron and steel work pieces and hence, it is understood that results are expected to changes and/or modifications on applying the specified parameters of triple point angled drill for higher/different diameter drills; and on work materials other than cast iron and steel. It is further understood that the appended claims are intended to cover all such changes and/or modifications that may fall within the spirit and scope of the present subject matter.