Method of shaping a metal rod material

Abstract: The present invention provides a processing method for easily shaping a tip of a metal rod material such that the sectional area of the tip gradually decreases. A metal rod material (3) is contained in a molding groove (2) which is disposed in a mold (1) and whose end (2a) has a sectional area smaller than that of the metal rod material (3). A rolling roller (4) is rolled in contact with a mold surface (1a), and the rod material (3) is plastically deformed and molded is accordance with the shape of the molding groove (2). Subsequently, a burr (3b) is removed. The molding groove (2) has a sectional area smaller than that of the metal rod material (3) at the tip end (2a), has a width and depth larger in size than a diameter of the rod material (3) at the rear end (2b), and has a gradually decreasing sectional area towards the tip end (2a). In one embodiment, a rolling roller (14) rotates together with large-diameter rollers (15a,15b), and is pressed in contact with the mold surface (1a) by the rollers (15a,15b). In a further embodiment, a rolling roller (16) rotates together with a large-diameter roller (17), and a plurality of rolling rollers are supported by a retainer ring (18) disposed coaxially with the roller (17) at the outer periphery of the roller (17), arranged around its circumference, and pressed in contact with the mold surface (1a) by the roller (17).

Description: The present invention relates to a method of processing a tip of a metal rod material to gradually reduce in sectional area the metal rod material. Examples of a product processed such that a sectional area of a metal rod material gradually decreases towards the tip of the material include a minus driver, a drill bit such as a triangular drill bit, and the like. As a conventional method for processing the tip of a minus driver, a method shown in FIG. 12 is known. According to the method, first as shown in FIG. 12A, a metal rod material 3 as a raw material is cut to a desired length, and next, as shown in FIG. 12B, a tip 21 is press molded to be flat. After the press molding, as shown in FIGS. 12C, 12D, side surfaces 21a, 21b of the tip 21 and the end surface of the tip 22 are ground in form, and the shape of the minus driver is formed. Subsequently, a burr generated during the grinding is removed by barrel grinding or the like, and the material is chamfered, so that a minus driver 6 is obtained as shown in FIG. 12E. With the minus driver 6 shown in FIG. 12E, produced by the aforementioned processing, the tip of the metal rod material 3 has a flat and tapered shape 5a whose sectional area gradually decreases. Moreover, a conventional method for processing the tip of a triangular drill bit is known, as shown in perspective and surface views in FIG. 13. According to the method, first as shown in FIG. 13A the metal rod material 3 as the raw material is cut to the desired length. Subsequently, as shown in FIG. 13B the tip is ground to form a conical tip 23, and next as shown in FIG. 13C the conical tip 23 is press molded to form a triangular pyramid tip. After press molding, as shown in FIGS. 13D, 13E, first, second and third surfaces 24a, 24b, 24c of the triangular pyramid tip 24 are ground in turn, and the shape of a triangular drill bit is formed. Subsequently, the burr generated during cutting is removed by electrolytic grinding, chemical grinding, and the like, and a cutting edge is used, so that a triangular drill bit 13 is obtained as shown in FIG. 13F. In the triangular drill bit 13 shown in FIG. 13F and obtained, by the aforementioned processing, the tip of the metal rod material 3 has a sharp triangular pyramid shape 5b whose sectional area gradually decreases. However, according to the conventional processing methods, a large number of steps are required until the tips of the minus driver 6 and triangular drill bit 13 are shaped. Therefore, the methods are disadvantageously intricate. The present invention has been developed to solve the aforementioned problem, and thus the present invention seeks to provide a method of processing for easily shaping a tip of a metal rod material whose sectional area gradually decreases. Prior art document US-A-4483168 discloses a method of processing a metal rod material according to the preamble of claim 1. According to the present invention, there is provided a method of processing a metal rod material, comprising the steps of containing the rod material in a molding groove which is disposed in a mold for molding the metal rod material and which has at least one end having a sectional area smaller than the sectional area of the rod material along a longitudinal direction of the rod material; pressing a rolling roller in contact with a mold surface having the molding groove, rolling/moving the rolling roller toward the end having the sectional area smaller than the sectional area of the rod material from the other end of the molding groove, and plastically deforming and molding the rod material in accordance with the shape of the molding groove by the rolling roller; and removing a burr formed of an excess material extruded out of the molding groove by the rolling roller during the plastic deformation, characterised in that said molding groove has a sectional area smaller than the sectional area of the metal rod material at a tip-end along the longitudinal direction of the metal rod material, wherein said molding groove,also has a width and depth larger in size than a diameter of the rod material at a rear-end, and has a sectional area which gradually decreases towards the tip end of the molding groove. According to the method of processing of the present invention, first the metal rod material as a raw material is contained in the molding groove of the mold. Any metal rod material can be used as long as the material has plasticity, but materials having no plasticity such as a cast material, sintered material and hardened material are inappropriate. Subsequently, the rolling roller is pressed in contact with the surface of the mold in which the metal rod material is contained in the molding groove, and rolled/moved toward the end having a sectional area smaller than that of the rod material from the other end of the molding groove. Then, with movement of the rolling roller, the metal rod material is pressed onto the molding groove by the rolling roller, plastically deformed along the molding groove, and molded in accordance with the shape of the molding groove. In this case, the sectional area of the molding groove is smaller than the sectional area of the metal rod material at at least one end along the longitudinal direction of the metal rod material. Then, the excess material of the metal rod material overflowing from the molding groove is extruded out of the molding groove by the rolling roller, and rolled between the maid and the rolling roller, and a foil-shaped burr is formed. Subsequent to the plastic deformation, the burr is removed, and the metal rod material having the tip shaped along the molding groove can be obtained. To remove the burr, barrel grinding is suitable when the tip of the material shaped along the molding groove needs to be chamfered. Moreover, when the tip requires a cutting edge, electrolytic grinding, chemical grinding, and the like are suitable for removing the burr. According to the method of the present invention, by a simple operation of containing the metal rod material in a molding groove disposed in a mold and pressing and rolling a rolling roller on the surface of the mold, the tip end of the metal rod material can obtain a shape whereby its sectional area gradually decreases. Therefore, a metal rod material having the tip shaped as described above can easily be molded. According to the method of the present invention, the molding groove has a sectional area smaller than the sectional area of the rod material at the tip-end along the longitudinal direction of the rod material, has a width and depth larger in size than a diameter of the rod material at the rear-end of the rod material, and has a sectional area gradually decreasing toward the tip end thereof. In the portion of the molding groove having a width and depth larger in size than the diameter of the metal rod material at the rear-end of the molding groove, the metal rod material is completely contained in the molding groove. Moreover, when the rolling roller is pressed and rolled onto the mold surface in the portion having the sectional area smaller than the sectional area of the metal rod material at the tip-end of the molding groove, the rod material can plastically be processed without any difficulty. Therefore, mold damage, particularly damage of the molding groove can be prevented. Moreover, since the sectional area of the molding groove gradually decreases toward the tip end, the metal rod material can smoothly and plastically be deformed along the molding groove. In the plastic deforming method of the present invention, the rolling roller is preferably rotated together with a roller having a diameter larger than a diameter of the rolling roller, pressed in contact with the mold surface by the large-diameter roller, and therefore protected by the large-diameter roller to prevent damage. Preferably, the rolling roller rotates together with the large-diameter roller, and a plurality of rolling rollers are supported by a retainer ring disposed coaxially with the large-diameter roller at the outer periphery of the large-diameter roller, and are arranged around the circumference of the large diameter roller. Therefore, even in this case, when the rolling roller is pressed in contact with the mold surface by the large-diameter roller, an action/effect similar to the aforementioned action/effect can be attained. In the plastic deforming method of the present invention, when the mold has a relatively small sectional area decrease ratio, preferably a large-diameter rolling roller is used. Moreover, in a mold whose sectional area decrease ratio is relatively large or which has zero section, a preferably small-diameter rolling roller is used. For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- FIG. 1 is a perspective view of a mold for use in a method of processing according to a first embodiment of the present invention. FIG. 2 is an explanatory sectional view showing the method of processing of the first embodiment. FIG. 3 is an explanatory sectional view showing the method of processing of the first embodiment. FIG. 4 is a sectional view taken along line IV-IV of FIG. 3. FIG. 5 is a plan view of a metal rod material obtained by the method of processing using the mold of FIG. 1. FIG. 6 is a sectional view taken along line VI-VI of FIG. 5. FIG. 7 is a plan view of the metal rod material obtained by the method of processing of the first embodiment. FIG. 8 is a perspective view of the mold for use in the method of processing according to a second embodiment of the present invention. FIG. 9 is a perspective view of the metal rod material obtained by the method of processing of the second embodiment. FIG. 10 is an explanatory sectional view showing an alternative example of a rolling roller for use in the respective embodiments. FIG. 11 is an explanatory sectional view showing another alternative example of the rolling roller for use in the respective embodiments. FIG. 12 is a perspective view showing one example of a conventional method for molding the metal rod material. FIG. 13 shows a perspective view and front view showing another example of a conventional method for molding the metal rod material. Embodiments of the present invention will next be described in detail with reference to the accompanying drawings. The first embodiment of the present invention is a process for molding a metal rod material into a minus driver. As shown in FIGS. 1 and 2, a mold 1 for use in the first embodiment has a quadratic prism molding groove 2. A sectional area of a tip end 2a of the molding groove 2 is 15 smaller than the sectional area of a metal rod material 3, and a rear end 2b of the groove has a width and depth larger in size than the diameter of the metal rod material 3. Moreover, the molding groove 2 has a sectional area gradually decreasing toward the tip end 2a from the rear end 2b thereof. In the first embodiment, as shown in FIG. 2, first the metal rod material 3 is contained in the molding groove 2, and a rolling roller 4 is pressed onto a mold surface 1a. Moreover, when the rolling roller 4 is pressed in contact with the mold surface 1a, the rolling roller 4 is rolled towards the tip end 2a from the rear end 2b of the molding groove as shown by arrows of FIG. 2. In this case, at the rear end 2b of the molding groove 2 shown in FIGS. 3A and 4A, the molding groove 2 has a width and depth larger in size than the diameter of the metal rod material 3. Therefore, the metal rod material 3 is completely contained and held in the molding groove 2, and 5 the rolling roller 4 is directly pressed onto the maid surface 1a. Moreover, in the middle portion of the molding groove 2 shown in FIGS. 3B and 4B, as the rolling roller 4 moves, the metal rod material 3 is pressed into the molding groove 2 having a gradually decreasing sectional area by the rolling roller 4. As a result, plastic deformation of the metal rod material 3 starts. Furthermore, at the tip end 2a of the molding groove 2 shown in FIGS. 3C and 4C, the metal rod material 3 is pressed into the molding groove 2 having a sectional area smaller than that of the metal rod material 3 by the rolling roller 4. As a result, the metal rod material 3 is plastically deformed along the molding groove 2, and formed in the shape of the molding groove 2. During the aforementioned treatment, the metal rod material 3 is completely contained in the molding groove 2 as described above at the rear end 2b of the molding groove 2, and plastically deformed along the molding groove 2 only towards and at the tip end 2a. Therefore, excess material 3a of the metal rod material 3 flows toward the tip end 2a. The processing can be performed without any difficulty, and damage of the mold 1, particularly damage to the molding groove 2 is avoided. Moreover, as shown in FIGS. 3B and 3C, the excess material 3a of the metal rod material 3 overflowing from the molding groove 2 is extruded out of the molding groove 2 by the rolling roller 4. As a result, as shown in FIG. 3D, the excess material 3a is rolled between the mold 1 and the rolling roller 4, and an extremely thin foil-shaped burr 3b is formed. In the first embodiment, when the rolling roller 4 rolls to a front part of the molding groove 2 as shown in FIG. 2, the roller moves onto the mold 1, and returns to a start position on the rear end 2b of the molding groove 2 as shown by the arrows of FIG. 2. While the rolling roller 4 is on the mold 1, the completely plastically deformed metal rod material 3 is removed from the molding groove 2, and a new metal rod material 3 is contained in the molding groove 2. Moreover, when the aforementioned procedure is repeated, plastic deformation of the metal rod material 3 can continuously be performed. As shown in FIGS. 5 and 6, the metal rod material 3 removed from the molding groove 2 has a flat and tapered tip shape 5a at the tip thereof. Moreover, in the tip of the metal rod material 3, the burr 3b is integrally formed at the periphery of the tip 5a, and a remaining non-rolled portion of the excess material 3a adheres to the tip end of the burr 3b. Subsequently, the tip of the metal rod material 3 shown in FIGS. 5 and 6 is subjected to barrel grinding, the burr 3b and excess material 3a are removed, the end of the tip of the metal rod material is chamfered, and a driver 6 is finally obtained as shown in FIG. 7. A second embodiment of the present invention will next be described. The second embodiment is a process for molding a triangular drill bit. As shown in FIG. 8, a mold 11 for use in the second embodiment has a triangular pyramid molding groove 12 in a surface 11a of the mold. The sectional area of a tip end 12a of the molding groove 12 is smaller than the sectional area of the metal rod material 3, and the rear end 12b of the groove has a width and depth larger in size than the diameter of the metal rod material 3. Moreover, the molding groove 12 has a sectional area gradually decreasing toward the tip end 12a from the rear end 12b thereof. In the second embodiment, the metal rod material 3 is contained in the molding groove 12 (not shown), the same treatment as that of the first embodiment shown in FIG. 2 is performed, the tip of the metal rod material 3 is plastically deformed along the molding groove 12, and the material is molded in accordance with the shape of the molding groove 12. As a result, a metal rod material 3 having a tip with a sharp triangular pyramid shape 5b is obtained as shown in FIG. 9A. The remarkably thin foil-sharp triangular pyramid shape 5b is obtained as shown in FIG. 9A. The remarkably thin foil-shaped burr 3b is integrally formed at the periphery of the tip of the metal rod material 3. Subsequently, the tip of the metal rod material 3 shown in FIG. 9A is ground, the burr 3b is removed, a cutting edge is used, and a triangular drill bit is finally obtained as shown in FIG. 9B. In order to sharpen the end of the tip of the triangular drill bit 13 to provide a cutting edge, electrolytic grinding or chemical grinding is preferably performed to grind the drill bit. In the aforementioned embodiments, the single rolling roller 4 is pressed and rolled on the mold surfaces 1a, 11a. Alternatively, a rolling roller 14 as shown in FIG. 10, or a rolling roller 16 as shown in FIG. 11 may also be used. The rolling roller 14 shown in FIG. 10 contacts rollers 15a, 15b larger in diameter than the rolling roller 14, and is pressed in contact with the metal rod material 3 by the rollers 15a, 15b. Either one of the rollers 15a, 15b is a driving roller, the other roller is a driven roller, and the rollers rotate together by contact friction with the rolling roller 14. When the rolling roller 14 is pressed by the rollers 15a, 15b, the roller is protected by the large diameter rollers 15a, 15b, and can be prevented from being damaged by the contact with the mold surfaces 1a, 11a. Moreover, a plurality of rolling rollers 16 are supported in an annular groove (not shown) disposed along an outer periphery of a roller 17 by a retainer ring 18 disposed coaxially with the roller 17 larger in diameter than the rolling roller 16, and arranged in contact with the outer periphery of the roller 17 about its circumference. In the embodiment shown in FIG. 11, the roller 17 serves as the driving roller, and the respective rolling rollers 16 rotate together by the contact friction with the roller 17. Similarly, as occurs with the rolling roller 14 shown in FIG. 10, the rolling rollers 16 are protected by the large-diameter roller 17, and can be prevented from being damaged by the press contact with the mold surfaces 1a, 11a. The molding of a minus driver 6 and a triangular drill bit 13 has been described in the aforementioned respective embodiments, but it will be appreciated that the processing method of the present invention can be used to molding other shapes as long as the tip of the metal rod material 3 is to have a shape having a gradually decreasing sectional area.

Claims: A method of processing a metal rod material, comprising the steps of-: containing the rod material (3) in a molding groove (2) which is disposed in a mold (1) for molding the metal rod material (3) and which has at least one end (2a) having a sectional area smaller than the sectional area of the rod material along a longitudinal direction of the rod material; pressing a rolling roller (4) in contact with a mold surface (1a) having the molding groove (2), rolling/moving the rolling roller toward the end (2a) having the sectional area smaller than the sectional area of the rod material (3) from the other end (2b) of the molding groove, and plastically deforming and molding the rod material in accordance with the shape of the molding groove by the rolling roller (4); and removing a burr (3a) formed of an excess material extruded out of the molding groove by the rolling roller (4) during the plastic deformation, characterised in that said molding groove (2) has a sectional area smaller than the sectional area of the metal rod material (3) at a tip-end (2a) along the longitudinal direction of the metal rod material (3), wherein said molding groove (2) also has a width and depth larger in size than a diameter of the rod material at a rear-end (2b), and has a sectional area which gradually decreases towards the tip end (2a) of the molding groove. The processing method according to claim 1, wherein said rolling roller (14, 16) is rotated together with a roller (15, 17) having a diameter larger than a diameter of the rolling roller, and pressed in contact with said rod material (3) by the large-diameter roller. The processing method according to any preceding claim, wherein said rolling roller (16) is rotated . together with a roller (17) having a diameter larger than a diameter of the rolling roller, and a plurality of rolling rollers (16) are supported by a retainer ring (18) disposed coaxially with the large-diameter roller (17) at an outer periphery of the large-diameter roller (17), arranged around its circumference, and pressed in contact with said rod material (3) by the large-diameter roller. The processing method according to any preceding claim, further comprising the steps of removing said burr by barrel grinding, and chamfering a plastically deformed portion of said rod material. The processing method according to any of claims 1 to 3, further comprising the steps of removing said burr by electrolytic grinding, and providing a plastically deformed portion of said rod material with a cutting edge. The processing method according to any of claims 1 to 3, further comprising the steps of removing said burr by chemical grinding, and providing a plastically deformed portion of said rod material with a cutting edge.

Inventors: NAKAYAMA SHINICHIRO, NAKAYAMA, SHINICHIRO
Applicants: NAKAYAMA SHINICHIRO, NAKAYAMA, SHINICHIRO
Application year: 2001
Main classification: B21H7
IPC codes: B21C5, B21K5, B21H7