AN IMPROVED SCREW AND A METHOD OF MANUFACTURING THEREOF

Abstract

The present disclosure provides an improved screw and method of manufacturing thereof. The method comprising the steps of manufacturing 101 the screw body by cold forging process using ferrous alloy, making 102 a hole 301 on the screw head 201 to form a base of the hole and a wall thickness 501 of the screw head 201 for providing an internal drive, forming 103 a layer 602 of hard ferrous alloy in the hole 301 with the screw head 201 wherein the layer 602 having high hardness than the screw body 200, optionally smoothening 104 the layer 602 using a conventional process and machining 105 the layer 602 to obtain the internal drive 601 thereby achieving increase in hardness and wear-resistance of the internal drive 601.

Claims

1. A method of manufacturing an improved screw, wherein said method comprising the steps of: manufacturing 101 the screw body 200 by cold forging process using ferrous alloy, characterized in that making 102 a hole on the screw head 201 to form a base of the hole 301 and a wall thickness 501 of the screw head 201 for providing an internal drive 601; forming 103 a layer 602 of hard ferrous alloy in the hole 301 with the screw head 201 wherein the layer 602 having high hardness than the screw body 200; and machining 105 the layer 602 to obtain the internal drive 601 thereby achieving increase in hardness and wear-resistance of the internal drive 601.

2. The method as claimed in claim 1, wherein the method further includes smoothening 104 the layer 602 using a conventional process prior to the machining 105.

3. The method as claimed in claim 1, wherein the forming 103 includes press fitting a pre-hardened rod 403 in the hole 301 to form the layer 602 made of the hard ferrous alloy in the hole 301.

4. The method as claimed in claim 3, wherein the press fitted pre-hardened rod 403 is welded 402 and joined with the screw head 201.

5. The method as claimed in claim 3, wherein top edge of the hole 301 is chamfered 401, wherein the press fitted pre-hardened rod 403 is welded 402 and joined with the screw 201 head at the chamfered edge 401.

6. The method as claimed in claim 3, wherein the hard ferrous alloy of the pre-hardened rod 403 is selected from a group comprising of high-speed steel, hard steel.

7. The method as claimed in claim 1 or 2, wherein the forming 103 includes depositing plurality layers of hard ferrous alloy in the hole 301 to form the layer 602 made of the hard ferrous alloy in the hole 301.

8. The method as claimed in claim 1, wherein the ferrous alloy of the screw body 200 is selected from a group comprising of ultra-high strength alloy, nickel alloy.

9. The method as claimed in claim 1, wherein size of the hole 301 is made larger than final dimension of the internal drive 601.

10. The method as claimed in claim 6, wherein the hard ferrous alloy is a steel wire 502.

11. The method as claimed in claim 6, wherein the hard ferrous alloy is powder.

12. The method as claimed in claim 10, wherein the steel wire 502 is a high speed steel wire 502.

13. The method as claimed in claim 7, wherein the deposition is performed using a welding process.

14. The method as claimed in claim 13, wherein the deposition is directed on the sidewall 505 of the screw head 201.

15. The method as claimed in claim 13, wherein the deposition is performed in moving upward direction by forming one layer 507 over another layer 506.

16. The method as claimed in claim 1, wherein the machining is performed using a spark erosion process.

17. The method as claimed in claim 1, wherein the high hardness is limited to a drive portion 601 of the screw which comes in contact with a driving tool.

18. An improved screw made of two dissimilar ferrous alloys comprising: a screw head 201; an internal drive 601 located on the screw head 201 which comes in contact with a screwdriver; a screw body 202 made of a ferrous alloy extending from the screw head 201; and threads 203 around the screw body 202; characterized in that said internal drive 601 portion of the screw head 201 is made with a dissimilar material and a high hardness ferrous alloy compared to rest of the screw.

19. The improved screw as claimed in claim 18, wherein the ferrous alloy having strength of at least 550 MPa used for making the screw body.

20. The improved screw as claimed in claim 18, wherein the hardness of the internal drive 601 is in the range up to 65 HRc.

21. The improved screw as claimed in claim 18, wherein the ferrous alloy of the screw body 200 is selected from a group comprising of ultra-high strength ferrous alloy, nickel alloy.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0028] The detailed description is set forth with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items.

[0029] FIG. 1 illustrates a flowchart 100 for method of manufacturing an improved screw, according to an embodiment herein;

[0030] FIG. 2 illustrates a screw body without an internal drive, according to an embodiment herein;

[0031] FIG. 3 illustrates the screw body with a hole, according to an embodiment herein;

[0032] FIG. 4A illustrates a chamfer on top edge of the hole, according to an embodiment herein;

[0033] FIG. 4B illustrates a welding of a pre-hardened rod having a hard hardness alloy, according to an embodiment herein;

[0034] FIG. 5A illustrates the screw body with deposition in the hole, according to another embodiment herein;

[0035] FIG. 5B illustrates the technique of deposition in the screw head, according to another embodiment herein; and

[0036] FIG. 6 illustrates the screw body with an internal drive, according to an embodiment herein.

LIST OF NUMERALS

[0037] 100flowchart for method of manufacturing an improved screw [0038] 101method for manufacturing screw body [0039] 102making a hole [0040] 103forming a layer [0041] 104smoothening the layer [0042] 105machining the layer [0043] 200screw body without an internal drive [0044] 201screw head [0045] 202screw body [0046] 203threads [0047] 204screw head without an internal drive [0048] 300screw body with a hole [0049] 301hole [0050] 400Ascrew body with a chamfer on edge of hole [0051] 400Bscrew head with a welding [0052] 401chamfer [0053] 402weld [0054] 403pre-hardened rod [0055] 500Ascrew head with deposition in the hole [0056] 500Btechnique of deposition in screw head [0057] 501wall thickness [0058] 502wire [0059] 503diameter of wire [0060] 504deposition [0061] 505side wall [0062] 506first deposited layer [0063] 507second deposited layer [0064] 508overlap [0065] 600screw body with an internal drive [0066] 601internal drive [0067] 602layer

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0068] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[0069] As mentioned above, there is a need to provide an improved screw which can provide increase in wear-resistance of the internal drive, so that the productivity and savings is increased in the applications such as found in indexable insert clamping. The preferred embodiments herein achieve this by providing an improved screw that has only its internal screw-drive, at the location where a driving tool meets the screw, selectively high in hardness in the range of up to 65 HRc, while the body is made of ferrous alloy such as ultra-high strength steel. Referring now to the drawings, and more particularly to FIGS. 1 through 6, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.

[0070] FIG. 1 illustrates a flowchart 100 for method of manufacturing an improved screw, according to an embodiment. In an embodiment, the method for manufacturing of an improved screw comprising the steps of manufacturing 101 the screw body by cold forging process using a ferrous alloy, making 102 a hole on the screw head to form a base of the hole and a wall thickness of the screw head for providing an internal drive, forming 103 a layer of a hard ferrous alloy in the hole with the screw body, the layer having high hardness than the screw body, and machining 105 the layer to achieve the internal drive thereby achieving increase in hardness and wear resistance of the internal drive. The method may optionally include smoothening 105 the layer using a conventional process before machining 104 the layer.

[0071] In an embodiment, the machining 105 can be performed using a process which includes but not limited to spark erosion process, and electrochemical process.

[0072] FIG. 2 illustrates a screw body 200 without an internal drive, according to an embodiment. Further, FIG. 2 correlates to the step 101 as depicted in the flowchart mentioning the method 100 to manufacture the improved screw. The screw comprises a screw head 201, a screw body 202 and threads 203. In an embodiment, the screw body 202 can be manufactured using a cold forging machine and by conventional processes without heat treatment. Raw materials of the screw body 202 can be selected from ferrous alloys such as ultra-high strength ferrous alloys, and high strength nickel alloy wire rod. The advantage of using the ultra high strength steels or ultra high strength ferrous alloys is to reduce the problems of screw breakage when it is lodged inside the indexable tool holder.

[0073] In an embodiment, the internal drive is not provided 204 in the screw head 201 at this stage 101, and therefore the internal drive of the screw is not cold forged at this stage 101, but only the screw body 202 and head 201 is manufactured. The external threads 203 are made on the screw using any conventional thread making processes such as thread rolling, according to an embodiment.

[0074] FIG. 3 illustrates the screw body 300 with a hole 301, according to an embodiment. Further, FIG. 3 correlates to the step 102 as depicted in the flowchart mentioning the method 100 to manufacture the improved screw.

[0075] According to an embodiment, a hole 301 is made 102 during or after the cold forging process on the screw head 201 to form a base of the hole and a wall thickness of the screw head 201 for providing an internal drive. Further, the hole 301 is performed at the exact location where the internal drive is required on the screw. In an embodiment, the hole 301 on the screw head 201 can be made 102 during the manufacturing the screw body 202. In another embodiment, the hole 301 on the screw head 201 can be made after the manufacturing the screw body 202. In an embodiment, the size of the hole 301 may be kept slightly larger than the final dimension of the internal drive. According to an embodiment, the making 102 of the hole can include but not limited to drilling or punching. Further, the hole 301 can be drilled using any conventional drilling method or made using a punch during the cold forging process.

[0076] FIG. 4A illustrates the screw body 400A with a chamfer 401 on top edge of the drilled hole 301, and FIG. 4B illustrates the pre-hardened rod 403 welded 402 onto the screw head 400B. Further, FIGS. 4A and 4B correlate to the step 103, as depicted in the flowchart mentioning the method 100 to manufacture the improved screw. In an embodiment, the forming 103 includes press fitting the pre-hardened rod 403 made of a hard ferrous alloy in the hole 301 to form the layer of hard ferrous alloy. The chamfer 401 having width d and depth c is provided on top edge of the hole 301. The dimensions of the chamfer 401 can be modified according to the size of the screw. In an embodiment, the pre-hardened rod 403 is welded 402 on the chamfered edge 401 of the hole 301 for forming a layer of hard ferrous alloy by securely joining it to the screw body. The material for pre-hardened rod 403 can be chosen including but not limiting from high speed steels or any other hard steel. The pre-hardened rod 403 made of a high speed steel exhibits higher hardness and higher wear resistance. In an embodiment, the diameter of the pre-hardened rod 403 is equal to hole diameter x and a length of the pre-hardened rod 403 is lesser than the hole length preferably the length of the pre-hardened rod 403 is lesser than the hole length 1 by approximately 30-100 microns. The pre-hardened rod 403 is press fitted in the hole 301 such that the pre-hardened rod 403 touches the base of the hole 301.

[0077] In an embodiment, the press fitted pre-hardened rod 403 is welded and joined with the screw head 201 without the chamfered edge. The welding of the pre-hardened rod 403 with the screw head 201 without the chamfered edge can be performed using a welding process that include but not limited to capacitive discharge welding, and friction stir welding. In another embodiment, the press fitted pre-hardened rod 403 is welded 402 and joined with the screw head 201 at the chamfered edge 401. The welding 402 of the pre-hardened rod 403 with the screw head 201 at the chamfered edge can be performed using a welding process that include but not limited to laser welding, GTAW using a filler wire. In a embodiment, the laser welding can be performed using a Nd:YAG laser welding machine. In a preferred embodiment, welding filler wire can be selected having high tensile strength and elongation properties, while using the welding filler wire for welding at 402. In an embodiment, diameter of the welding filler wire is approximately equal to height d of the chamfer 401.

[0078] FIG. 5A illustrates the screw body 500A with deposition in the hole, and FIG. 5B depicts the technique of deposition in the screw head 500B, according to an embodiment. Further, FIGS. 5A and 5B also correlate to the step 103, as depicted in the flowchart mentioning the method 100 to manufacture the improved screw.

[0079] According to an embodiment, the forming 103 includes depositing the hole 301 of the screw head 201 and filling 504 with a material having a high hardness than the screw 201 body to form the layer, wherein the material includes but not limited to a tool steel wire 502, other hard ferrous alloy, powder and so on. Further, the deposition can be performed using a welding process. In a preferred embodiment, a high-speed steel wire can be used for deposition owing to its superior hardness and metal-to-metal wear resistance. The size 503 of the wire 502 can be chosen based on the size of the screws, according to an embodiment.

[0080] In an example, smaller size screws may require smaller diameter wires 502. According to an embodiment, the diameter 503 of the wire 502 may not exceed the wall thickness 501 of the screw head 201.

[0081] According to an embodiment, the deposition of the wire 502 can be performed using a welding equipment that emits low heat just enough to weld the wires 502 on the screw. For example, Nd: Yag Laser welding machine, GTAW machine with low amperage capability (2 Amps to 15 Amps) etc.

[0082] According to an embodiment, the chosen wire 502 can be deposited by melting it using the laser pulse from the welding machine. Accordingly, the deposition can be started from base of the hole 301 moving up one layer 506 over another layer 507 as shown in FIG. 5B. In a preferred embodiment, a 20% overlap between adjacent layers 508 may be provided. Further, the deposition can be directed on the sidewall 505 instead of on the base of the hole 301. In an embodiment, the hole 301 may not be completed filled up inside, but only deposited on the sidewall 505 of the hole, thus providing deposited layer with a small centerline in the hole 301.

[0083] The step 104 as shown in FIG. 1 is related to the smoothening of the deposited surface with the help of the conventional processes. The smoothening 104 can be performed using any conventional process, for example, grinding the unevenness of the deposited surface to make it machined and smooth. This is a preparatory step prior to the step of machining the deposited layer.

[0084] FIG. 6 illustrates the screw body 600 with an internal drive 601 in the screw head 201, according to an embodiment. Further, FIG. 6 correlates to the step 105, as depicted in the flowchart mentioning the method 100 to manufacture the improved screw. A layer 602 of higher hardness than the screw body 202 is formed on the internal drive 601.

[0085] According to an embodiment, the hardness of the pre-hardened rod 403 can vary according to the material of the pre-hardened rod 403. Using pre hardened high speed steel rod increases hardness and wear resistance, thereby achieving high hardness and wear resistance of the layer 602 on the internal drive 601.

[0086] According to another embodiment, the deposited layers 506/507 can become hard owing to the re-melting of the tool steel wires 502. In an embodiment, the hardness of the deposit can vary according to the type of wire 502 used. Accordingly, the screw head 201 with the deposited layers 506/507 can exhibit near tool steel like hardness.

[0087] According to an embodiment, the layer 602 can be machined using a process, wherein the process includes but not limited to spark erosion process (also referred as Spark Electrical discharge machining process, spark machining, die sinking, etc) and electrochemical process to obtain an internal drive 601. In an embodiment, the layer 602 can be machined to obtain the internal drive 601 having a shape including but not limited to Hex, Hexalobular and so on.

[0088] According to an embodiment, the electrodes required for the spark EDM machining of a chosen drive can be manufactured separately using a Wire-EDM or any other conventional process.

[0089] According to an embodiment, an improved screw made of two dissimilar ferrous metals using the method 100 is provided, wherein the improved screw comprising of a screw head 201, an internal drive 601 located on the screw head 201 which comes in contact with a driving tool such as a screwdriver, a screw body 202 made of a ferrous alloy extending from the screw head 201, threads 203 around the screw body 202, and only the internal drive 601 portion of the screw head 201 is made with a dissimilar material and a high hardness ferrous alloy compared to rest of the screw.

[0090] Accordingly, the screw body 201 is made with the ferrous alloy having strength at least 550 MPa. In further embodiment, the ferrous alloy of screw body is selected from a group comprising of ultra-high strength steel alloy, nickel alloy. In an embodiment, the hardness of the internal drive 601 can be in the range of up to 65 HRc.

[0091] According to an embodiment, the screw thus manufactured has its internal drive selectively high in hardness screw in the range of up to 65 HRc while the body is made of ferrous alloy such as ultra-high strength steel.

[0092] A main advantage of the present disclosure is that the improved screw thus manufactured with selectively hardened internal drive that increases wear-resistance thus improves productivity and saves cost of the industry is provided.

[0093] Another advantage of the present disclosure is that the screws thus manufactured have higher hardness in their internal drive and because of this feature the internal screw-drive remains more wear resistant and consequently the service life of the internal screw-drive is extended by several times.

[0094] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.