Abstract: A sintered gear comprises: plural tooth portion having a tooth flank and a tooth bottom land; a high density area formed over entire surface of the tooth portion, the high density area having a density of 7.6 Mg/m3 or more and formed with a depth of 1 mm or more from the surface; a low density area formed in deeper area than the high density area, the low density area having a density of 7.3 Mg/m3 or less; and an intermediate area formed between the high density area and the low density area, the intermediate area having a density gradient in which the density is gradually decreased from the high density area to the low density area.

Abstract: A die apparatus and method for performing a flashless forging operation to manufacture the toothed portion of a steering rack. The die apparatus includes first and second die members and at least one punch member, each having a forming surface shaped substantially as the obverse of a portion of the toothed portion. At least a portion of the forming surface of the first die member is shaped substantially as the obverse of the teeth of the rack. The first and second die members are moveable towards each other to a closed position, thereby partially forging the toothed portion from a blank placed in the die apparatus, and forming a substantially closed cavity defined by the forming surfaces. The punch member is adapted to move into the cavity once the die members are in the closed position, thereby completing the forging operation.

Abstract: A method for forming a gear, including the following steps: first obtaining a billet, then carrying out a backward extrusion process of the billet to form a forged billet with a blind hole by using a mold, and the forged billet has an appropriate axial length and an appropriate radial length. Then, a precise piercing process is carried out to remove the solid billet portion remained in the blind hole of the forged billet to form a through hole. Then, trimming of the through hole is carried out to form a high-precision inner hole, and positioning is carried out based on the high-precision inner hole to implement a pressing process of an outer tooth shape of the forged billet to form the gear.

Abstract: A gear and a method of making a forged powder metal gear having a plurality of teeth and a variable case depth profile forged in the plurality of teeth. Each tooth of the plurality of teeth has a first surface and a tooth root. A variable case depth profile is formed in each tooth of the plurality of teeth, whereby the variable case depth profile exhibits greater tooth wear resistance on the first surface and greater impact resistance in the tooth root.

Abstract: A gear wheel includes multiple helical toothings, each having a different helical angle. A pressing method for molding a gear wheel involves introducing a compactable material into a chamber of a pressing tool, compacting the material, exposing the helical toothings of the gear wheel, and removing the molded body from the pressing tool. A pressing tool for pressing, as one part, a gear wheel, includes a matrix, cylindrical first and second molding tool parts which can be translated along and then rotated about a longitudinal axis, and a driver coupled to the molding tool parts or driving them. The molding tool parts can be moved towards and away from each other and the inner surface of the matrix delimits the chamber and is shaped to allow a linear axial sliding movement of the compactable material relative to the matrix.

Abstract: The present invention provides a method for manufacturing a rigid internal gear for a wave gear device comprising an internally toothed portion and a gear main body portion comprised of different materials. In this method, a gear main body ring for forming a gear main body portion is preformed using a first aluminum alloy powder; an internal teeth-forming ring is preformed using a second aluminum alloy powder that has lower processability, is less durable, has higher abrasion resistance, and is harder than the first aluminum alloy powder; the internal teeth-forming ring is fitted inside the gear main body ring and the assembly is integrated by powder forging; and the resulting ring-shaped forging is subjected to post-processing, including cutting teeth. The gear main body portion and internally toothed portion are securely integrated by powder forging, and a lightweight rigid internal gear with high durability can therefore be obtained.

Abstract: A method of manufacturing a rack guide base body wherein a cavity (40) is formed which has a pair of semicylindrical convex surfaces (44a and 44b) and a pair of flat surfaces (45) each located between the semicylindrical convex surfaces (44a and 44b), and has a recessed surface (41) located on one axial end portion side inwardly of the semicylindrical convex surfaces (44a and 44b) and the flat surfaces (45) and a cylindrical surface (42) located on the other axial end portion side inwardly of the semicylindrical convex surfaces (44a and 44b) and the flat surfaces (45); a hollow portion (9c) is formed for allowing the cavity (40) to communicate with a hollow portion (10c) at one flat surface (45) and with a hollow portion (8c) at the other flat surface (45); a rack guide base body (50) is die cast by forcing molten metal of aluminum from the hollow portion (10c) into the cavity (40); and runners (56) integrally joined to flat surfaces (55) of the rack guide base body (50) formed by the respective flat surfaces

Abstract: The invention relates to a method for cold-form profiling cylindrical, thin-walled hollow parts (1), comprising profiles (4) which extend in an essentially parallel manner in relation to the longitudinal axis (A) of the hollow part (1). At least one profiling tool (5) engages in a strike-like hammering manner with the outside of the hollow part (1) in a radial manner in relation to the longitudinal axis (A) of the hollow part (1). The profiling tool (5) engages, respectively, in an essentially vertical and oscillating manner on the surface of the hollow part (1). Then, the profiling tool (5) is displaced in an axial manner in relation to the hollow part (1) at a constant radial adjusting depth until the desired profile length is obtained.

Abstract: A method for forming a component includes forming a workpiece into a hollow preform cylinder concentric with an axis and including an inner surface that extends along the axis, placing within the preform cylinder a mandrel having an outer surface, flow-forming the inner surface and the outer surface of the preform cylinder such that the inner surface of the cylinder conforms to at least a portion of the outer surface of the mandrel, and cutting the flow formed cylinder transversely with respect to the axis into segments, each segment having an axial length.

Abstract: A method for forming a component that transmits torque in an automatic transmission includes forming a workpiece with a hub concentric with and extending along an axis and forming the workpiece with a disc that is integral with the hub and extends radially outward from the hub. A hollow perform cylinder is formed integrally with the disc, located at a radial end of the disc distant from the hub, concentric with the axis, and includes an inner surface and an outer surface. A hollow perform cylinder is flow-formed using a flow-forming mandrel located within the cylinder and having an outer surface formed with gear teeth such that the inner surface of the cylinder conforms to at least a portion of the gear teeth on the flow-forming mandrel.

Abstract: An apparatus for extruding helical teeth in a gear blank includes a press including a die plate and a die base, the die plate being movable along an axis relative to the die base, the die base supporting the gear blank. A mandrel, aligned with the axis and moveable with the die plate along the axis, includes a surface that includes helical die teeth. A servo motor drives the mandrel in rotation about the axis to the required helix angle as the mandrel moves axially relative to the gear blank.

Abstract: A method of manufacturing a part with a tooth profile by cold forging includes an initial step of forming a initial tooth profile and a finishing step of forming a completed tooth profile by sizing. Between the initial step and the finishing step, is an intermediate step tooth thickness of the initial tooth profile is either maintained or reduced by 10% or less from the tooth thickness of the initial tooth profile. In the intermediate step an addendum part is expanded beyond the initial tooth profile by cold forging.

Abstract: A welded metal product includes a first metal plate having a first surface and a second surface opposed to the first surface; and a second metal plate being cold-pressure welded with the second surface of the first metal plate by directly pressing the first metal plate with the die. The first surface has a recess portion which is deformed by directly pressing with a die. A hardness of the first metal plate is greater than a hardness of the second metal plate.

Abstract: A steering rack for a vehicle rack and pinion steering gear and a method of manufacturing a steering rack includes a first member having a toothed region, attached to a tubular second member, the second member includes a bore, the cross section of the bore being circular along the length of the second member. The second member has at least one region of increased wall thickness and reduced bore diameter formed by an upsetting operation.

Abstract: A sprocket is formed by fine-blanking a steel plate using a die having a cutting edge shaped to produce rounded edges on the back sides of the sprocket tooth heads, and protrusions on the front sides. Thereafter the edges of the front sides of the sprocket tooth heads are formed in a press so that the protrusions are removed, and the edges of the front sides of the sprocket tooth heads have a rounded cross-sectional shape substantially the same as that of the edges of the front sides.

Abstract: The present invention is a method of forging a bevel gear, comprising: a first forging step in which a first intermediate article is obtained by pressing a blank, such that there is formed a preliminary one-end recessed part that is axially recessed in an axis-center part on an axially one-end side and/or a preliminary other-end recessed part that is axially recessed in an axis-center part on an axially other-end side; a second forging step in which a second intermediate article is obtained by pressing the first intermediate article in a hermetically sealed cavity space defined by a first die and a second die that is positioned opposedly to the first die in the axial direction, such that there are formed: a body part including a tooth part on a radially circumference thereof and a one-end recessed part that is axially recessed in an axis-center part on the axially one-end side; and a projecting part projecting from a rear surface part of the body part on the axially other-end side; and a through-hole forming

Abstract: A forging stock formed by extrusion such that its cross section perpendicular to the direction of extrusion varies along the direction of extrusion. The forging stock is cut into portions in the direction of extrusion to be forged individually, each cut portion having cross sections varying along the direction of extrusion. Each cut portion includes a pair of first parallel parts at both ends thereof in the direction of extrusion, a second parallel part, which is between the first parallel parts, and which differs in thickness from said first parallel parts, and oblique parts each of which is between the first parallel parts and the second parallel part.

Abstract: The one end side portion is nipped by a jig including a jig member having a pair of convex portions which are to be fitted to a depressions in contact with a tooth side face and a inclined portion and positioning a bar and a jig member which is to be clamped/opened with respect to the jig member. A die having an inside diameter smaller than the diameter of the outer periphery is pressed onto the outer periphery of the end portion of the cylindrical end side portion projected from the jig up to a press-in depth determined preliminarily based on the rack, so as to reduce the diameter of the end portion.

Abstract: A helical gear having helical tooth portions of the helical gear being worked by a punch and a die having a land of a smaller distance between opposed working surfaces formed to be inclined than that of other portion, formed on predetermined portions in tooth directions of respective opposed working surfaces thereon, in which worked surfaces on both side of the helical tooth portions on the helical gear as a work are ironed by the land in response to the helical tooth portions passing through the land when the work is forged by the punch.

Abstract: The present invention relates to a method for manufacturing a toothing on a component 2 of a shaft/hub connection, the component 2 being held permanently in a chucking 3 while it receives an at least two-stage toothing in this chucking. A special draw die 4 for carrying out the method is also proposed, a first toothing-forming region 14 with a first height and at least one following second toothing-forming region 15 with at least one second height being arranged between a first and a second end face 5, 6 and the first height being designed to be lower than the second height.

Abstract: A method of manufacturing a steering rack for a vehicle rack and pinion steering system. The rack comprises gear teeth and a shank that has a constant outside diameter and constant wall thickness over the majority of its length. The method comprises performing a forging operation on a tubular member with an elongate member positioned in the bore of a thickened region of the tubular member. The forging operation forms the gear teeth on the thickened region, and the elongate member is retained within the tubular member. The tubular member is made by performing a forming operation on a length of tube stock such that the outside diameter of the thickened region is smaller than the outside diameter of the shank, and the wall thickness of the thickened region is larger than the wall thickness of the shank.

Abstract: A method for manufacturing a clutch housing comprises: a first step of forming a work into a pre-product having a shaft portion and an outer drum portion enclosing the shaft portion integrally with the shaft portion; a second step of subjecting the pre-product to predetermined processing; and a third step of providing a spline on an inner periphery of the outer drum portion by flow forming, and forming the clutch housing into an almost completed product, wherein in the first step, an outer peripheral cylindrical portion of the outer drum portion is formed while being offset in an axial direction with respect to the shaft portion so that it is not opposite to at least part of the shaft portion in a radial direction.

Abstract: Disclosed herein are a helical gear forging apparatus wherein a forming introduction portion thereof, used to form gear teeth of the helical gear, is variable in shape on the basis of the desired helix angle of the gear-teeth so as to constantly keep a predetermined outer diameter of the formed gear teeth, thereby enabling easy forming of the helical gear irrespective of a variation of the helix angle, and a forging method using the same. The forging apparatus comprises a gear die having a gear teeth forming section defined at an inner circumference thereof for forming gear teeth of the helical gear, a collar die integrally formed at an upper end of the gear die, a lower die located below the gear die, a punch located above the collar die and adapted to push a stock into the collar die, and a knock-out located below the lower die and adapted to discharge the molded stock to the outside.

Abstract: A method for manufacturing a gear, wherein the gear is formed on a forging process by a die having an inner peripheral surface. A plurality of top surfaces corresponding to a bottom surface of the gear and both projected side surfaces corresponding to tooth surfaces of the gear and sandwiching the top surface connect smoothly to each other. The tooth surfaces and the bottom surface of the formed gear connect to each other smoothly. The forging process is carried out as a hot forging process in which the gear is formed by a hot forging die, or the forging process is carried out as a cold forging process in which the gear is formed by a cold forging die.

Abstract: A sintered gear comprises: plural tooth portion having a tooth flank and a tooth bottom land; a high density area formed over entire surface of the tooth portion, the high density area having a density of 7.6 Mg/m3 or more and formed with a depth of 1 mm or more from the surface; a low density area formed in deeper area than the high density area, the low density area having a density of 7.3 Mg/m3 or less; and an intermediate area formed between the high density area and the low density area, the intermediate area having a density gradient in which the density is gradually decreased from the high density area to the low density area.

Abstract: A production method for complex bearings includes: preparing an outer member and a cylindrical sintered bearing member. The outer member includes a fitting hole having: an almost circular cross section; an inner peripheral surface; and a surface roughness of the inner peripheral surface which is 3.2 to 100 ?m at a maximal height. The sintered bearing member includes: an outer diameter allowing clearance fit of the sintered bearing member into the fitting hole of the outer member. The production method further includes: inserting the sintered bearing member into the fitting hole of the outer member and inserting a columnar core rod into an inner peripheral surface of the sintered bearing member; and compressing the sintered bearing member in an axial direction.

Abstract: A method is disclosed for making a differential housing having a ring gear integrally formed therein. The method includes the steps of forging a conical frustum from a steel rod; deforming the frustum between upper and lower die halves of a tool to produce a differential housing having an annular rim; and forging a plurality of teeth in the annular rim defining the rim gear.

Abstract: A rack (20) for a rack and pinion steering system (10) includes a fully dense powder metal rack tooth section (50) joined, by sintering, to a hollow rack tube (30). The rack tooth section (50) is formed by pressing powder metal (70) into a die assembly (60) having internal rack tooth forms (68). The rack tube (30) and the pressed powder metal (70) are sintered to complete formation of the rack (20).

Abstract: A system for forging a rack bar from a blank pipe. A blank pipe 1 is held between dies 2 and 3. Stockers 7L and 7R are arranged on respective sides of the die set. In the stockers 7L and 7R, left-handed shuttles 6L1, 6L2, 6L3, . . . 6Ln and right-handed shuttles 6R1, 6R2, 6R3 . . . 6Rn are stored. First, a left-handed presser rod 5L inserts the shuttles 6L1 to the blank pipe from the left-handed stocker 7L. Then, a right-handed presser rod 5R inserts the shuttles 6R1 to the blank pipe from the right-handed stocker 7R, causing the shuttles 6L1 to be entrained and returned to the left-handed stocker 7L. Vertical shift movement is alternately executed between the left-handed and right-handed stockers 7L and 7R, so that a shuttle of step-likely increased working height is selected for executing a working process.

Abstract: A method for producing an annular element having an inner toothing, especially a sliding sleeve. An outlet ring element can be arranged in an extrusion device which includes an annular matrix element with an inner bore hole, a sleeve stamping device which is arranged therein and has first and second annular sleeve stamping elements which can be moved in relation to each other in the inner bore hole, and an inner stamping device having first and second inner stamping elements and first and second partial regions which are interspaced in the circumferential direction. When the inner stamping device is closed, the partial regions form cavities for producing the inner toothing. The outlet ring element is arranged between the first and second inner stamping elements and is measured in such a way that when closing the sleeve stamping device, material from the outlet ring element flows into the cavities for the formation of the inner toothing.

Abstract: A gear wheel includes multiple helical toothings, each having a different helical angle. A pressing method for molding a gear wheel involves introducing a compactable material into a chamber of a pressing tool, compacting the material, exposing the helical toothings of the gear wheel, and removing the molded body from the pressing tool. A pressing tool for pressing, as one part, a gear wheel, includes a matrix, cylindrical first and second molding tool parts which can be translated along and then rotated about a longitudinal axis, and a driver coupled to the molding tool parts or driving them. The molding tool parts can be moved towards and away from each other and the inner surface of the matrix delimits the chamber and is shaped to allow a linear axial sliding movement of the compactable material relative to the matrix.

Abstract: A differential assembly for a motor vehicle includes a plurality of pinion gears in meshing engagement with a plurality of side gears. At least one of the pinion gears and side gears is formed from a tubular insert and a tubular preform forged together in a forging die. A method for manufacturing a differential assembly is also provided.

Abstract: A method and an apparatus are described for producing a gear wheel from a powder metal blank (1) which is sintered and pressed with an overmeasure in the flank and root region of the teeth and which in the region of the overmeasure is densified under plastic deformation by the overmeasure by pressing in a counter-toothing (3) of a pressing tool (2) which engages in the toothing (4). In order to provide advantageous conditions it is proposed that during the plastic deformation of the flank or foot region of the tooth, the tip surface of the respective tooth is subjected to a pressure force counteracting an extension of the tooth.

Abstract: A one piece extruded differential side gear comprising internal splines which are used to connect to a drive shaft. The differential side gear includes outer circular gear teeth and defines a rectilinear blind hole in which an end portion of the drive shaft is received. The circular gear teeth and the blind hole are coaxially oriented along an axis of the differential side gear.

Abstract: A process for manufacturing ratchet wheels including the steps of: forming a cylindrical forging billet by hot or cold forging, the forging billet having a thru hole of inter-communicating recesses which are pre-formed in a forging die; providing a broach having teeth formed thereon; machining the forging billet into a workpiece having a sidewall with two annular grooves on the sidewall; forming a semi-product having a driving recess which is complementary in shape to the teeth by operating the broach through the workpiece along the thru hole; and forming a finished product having a plurality of teeth on a sidewall thereof by milling the semi-product.

Abstract: A method of manufacturing a friction plate including a plurality of frictional material segments which are punched into a predetermined shape, and a core plate onto which the plurality of frictional material segments are annularly bonded, comprising step of punching out the frictional material segment in such manner that an edge portion thereof along the predetermined shape is given a punching load earlier than the other portions thereof in the process of punching.

Abstract: A synchronizer sleeve adapted for use in a gear synchronizer mechanism of a power transmission, the synchronizer sleeve being formed at its inner periphery with inner spline teeth for meshing engagement to be meshed with a clutch gear of a change-speed gear train and inner spline teeth for synchronization positioned among the inner spline teeth for meshing engagement in a circumferential direction to be meshed with a synchronizer ring, wherein the inner spline teeth for meshing engagement and for synchronization are provided respectively at their one ends with a pair of chamfer surfaces formed by plastic deformation in a press-process, and wherein the inner spline teeth for synchronization are formed shorter in axial length than the inner spline teeth for meshing engagement. In the synchronizer sleeve, a ridge of each pair of the chamfer surfaces and an intersection of each of the chamfer surfaces and each tooth flank of the inner spline teeth are rounded off by plastic deformation in the press-process.

Abstract: A method of producing a bevel gear, particularly a bevel ring gear, the bevel gear comprising mounting surfaces. The method comprising the steps of flashless warm forging a blank, preferably an annular blank, in a forging die to produce the bevel gear with precision forged teeth; performing a hardening operation on the teeth; and then, without machining, finishing the teeth by lapping the teeth with a mating bevel gear. A die apparatus for use in a press for forging the bevel ring gear from the annular blank is also disclosed.

Abstract: A differential assembly for a motor vehicle includes a plurality of pinion gears in meshing engagement with a plurality of side gears. At least one of the pinion gears and side gears is formed from a heated tubular preform in a forging die. A method for manufacturing a differential assembly is also provided.

Abstract: A clutch gear having a boss part with a spline which is formed on an outer peripheral surface of the boss part formed on an axial end surface of the clutch gear having jaw clutch teeth formed on an outer peripheral surface thereof, in which the boss part, with the spline formed on outer peripheral surface thereof, is formed integrally and coaxially with the clutch gear having the jaw clutch teeth formed on the outer peripheral surface thereof by forging, the diameter of the boss part is shorter than that of the clutch gear, and an end part of an effective portion of the spline comes to at least an end surface of the clutch gear.

Abstract: A hollow rack shaft is manufactured through a first step, a second step and a third step. At the first step, the plate-like workpiece of substantial rectangular shape is press-formed into a gutter-like shape. At the second step, a row of rack teeth is press-formed by a preliminary forming step and a main forming step on the flat bottom portion of the workpiece formed in the first step. The die set used at the second step is provided with a recess for releasing surplus workpiece material within the die clearance at a stroke end of the pressworking and each die set is divided into a plurality of segments at the recess. At the third step, each of a pair of legs of the workpiece is bent in a semi-circular shape so as to be butted to each other.

Abstract: The support body engaged with the interior side of the tooth body provided at the worm wheel of the electric power steering apparatus comprises: a corrugated cylinder part press-formed to have a plurality of concavities on the exterior side thereof and convexities to the interior formed by the concavities which are arranged in a peripheral direction; and a plate part an exterior edge of which is united with an end of the corrugated cylinder part, wherein the tooth body is engaged with the exterior side of the corrugated cylinder part. With the method of manufacturing the gear, synthetic resin of the tooth body can be deposited uniformly on the support body made of metal engaged with the interior of the tooth body, costs can be reduced, and the support body can be engaged with the tooth body without generating voids and weld marks.

Abstract: Methods are provided for forming a hollow rack shaft from a workpiece comprising a rectangular plate. The workpiece is first bent into a gutter-like shape using a first die set. Rack teeth are then press-formed in a portion of the gutter-like shape using a second die set. The legs, or sides, of the workpiece are then bent around a mandrel into a semi-circular shape so as to butt against each other. Preferably, the die sets and mandrel may be adapted to improve the resulting hollow rack shaft.

Abstract: Idler gear as an example of gears having a part worked by cutting, and method and apparatus for manufacturing the same in which the chamfer part is formed at least in a portion between a tooth form with chamfers formed by forging process on an outer peripheral surface and the end part thereof in the axial direction by cutting.

Abstract: A workpiece for a hollow rack shaft is a substantially rectangular plate. The opposite two sides of this workpiece are respectively provided with a complementary profile composed of the continuation of a convex portion and a concave portion and when the workpiece is cylindrically formed, the profiles are mutually engaged. As the width of a part the width of which is the largest in the convex portion is larger than that of a part the width of which is the smallest in the concave portion, the two sides are prevented from being detached after engagement. Further, the opposite convex portion and concave portion are mutually caulked and hereby, mutual gap is removed.

Abstract: A full form net shape roll finished contacting machine element such as a gear or sprocket is produced from a near net shape workpiece of wrought or forged steel including teeth with an initial outer peripheral contoured surface, each having a tooth flank with a nominally involute surface and a root/fillet region with a trochoidal surface. A rolling die is rotatably supported on a first axis. With the workpiece rotatably supported on a parallel distant second axis, the rolling die is advanced in an in-feed direction to meshingly engage with the workpiece. The involute surface of each tooth of the rolling die engages the involute surface of a mating tooth of the workpiece and the tooth tip of the rolling die engaging the trochoidal root/fillet surface between adjacent mating teeth of the workpiece to effect material flow along the outer peripheral contoured surface. This process continues for all of the teeth of the workpiece.

Abstract: A hollow rack shaft is manufactured through a first step, a second step and a third step. At the first step, the plate-like workpiece of substantial rectangular shape is press formed into a gutter-like shape. The first die set used at this step is provided with slant die surfaces for canceling elastic recovering generated at the workpiece when the workpiece is removed from the first die set. At the second step, a row of rack teeth is press-formed on the flat bottom portion of the workpiece formed in the first step. The die set used at the second step is provided with a recess for releasing surplus workpiece material within the die clearance at a stroke end of the pressworking. At the third step, each of a pair of legs of the workpiece is bent in a semi-circular shape so as to be butted to each other. At this time, a mandrel is inserted between the legs of the workpiece.

Abstract: A method for making a gear with 90-180 teeth includes step 1 of forging an initial product of the gear; step 2 of annealing the initial product of the gear; step 3 of trimming the initial product of the gear; step 4 of grinding the initial product of the gear; step 5 of rolling the initial product of the gear to have 90 to 180 teeth; step 6 of proceeding the gear in step 5 with a heat treatment; and step 7 of proceeding the gear in step 6 with surface treatment.

Abstract: The support body engaged with the interior side of the tooth body provided at the worm wheel of the electric power steering apparatus comprises: a corrugated cylinder part press-formed to have a plurality of concavities on the exterior side thereof and convexities to the interior formed by said concavities which are arranged in a peripheral direction; and a plate part an exterior edge of which is united with an end of said corrugated cylinder part, wherein the tooth body is engaged with the exterior side of the corrugated cylinder part. With the method of manufacturing the gear, synthetic resin of the tooth body can be deposited uniformly on the support body made of metal engaged with the interior of the tooth body, costs can be reduced, and the support body can be engaged with the tooth body without generating voids and weld marks.

Abstract: The disk has a traction surface having a concave-arc-shaped cross section which is interposed between a small diameter end portion and a large diameter end portion. In the central portion of the end face of the disk on the small diameter end portion side, there is formed a through hole which extends through the disk up to the large diameter end portion side end face of the disk, while the inner peripheral surface of the through hole is used as an inside diameter surface of the disk. Here, when, among metal flows existing in the disk, a metal flow, which has such a positional relationship with respect to the surface of the disk that an angle ? formed between a metal flow on the traction surface side and the tangent of the traction surface is smaller than or equal to 30 degrees, is defined as a “metal flow along the disk surface”, the disk is structured such that the “metal flow along the disk surface” exists at least in the traction surface.