Abstract: In a tapered roller bearing, a large-diameter-side annular portion includes large-diameter-side pocket surfaces opposed to large end surfaces of respective tapered rollers; and oil retaining recesses each having an opening spanning an inner peripheral surface of the large-diameter-side annular portion and each of the large-diameter-side pocket surfaces. Each of the oil retaining recesses has an inner surface having a radially inwardly facing surface portion which is an inclined surface that is radially inwardly inclined toward the corresponding tapered roller.

Abstract: A rolling bearing includes an inner ring, an outer ring, rolling elements, and a retainer that holds the rolling elements. The retainer includes a metal portion and a sliding resin portion The metal portion has communication holes each having a plurality of openings on the surface of the metal portion, and the sliding resin portion is disposed in the communication holes.

Abstract: The invention relates to a rolling element bearing cage formed of one or more segments, each segment comprising: a supporting frame having a plurality of spaced apart openings each for accommodating a rolling element; and a reinforcing frame, inserted within the supporting frame, having a corresponding plurality of openings each for aligning with the openings of the supporting frame.

Abstract: A bearing cage assembly is disclosed herein that includes a first cage half formed as a plastic cage and a second cage half formed as a metal shell. The first cage half includes a first base rim and a first plurality of arms extending axially from the first base rim. The second cage half includes a second base rim and a second plurality of arms extending axially from the second base rim. The second plurality of arms are each formed by a first flange and a second flange. The first flange and the second flange are spaced apart from each other in a radial direction to define a receptacle dimensioned to receive a respective one of the first plurality of arms. Free ends of the first flange and the second flange are crimped over to retain the first cage half with the second cage half.

Abstract: A rolling-element bearing unit for use in a motor vehicle wheel or in a motorbike rocker arm includes outer and inner raceway elements and a set of rolling elements between the inner and outer raceway elements such that the inner and outer raceway elements are pivotable or rotatable relative to each other and also a lubricant reservoir body in the bearing interior for storing and dispensing a lubricant, the body including bridge elements extending between adjacent pairs of the rolling elements and a side ring connecting the bridge elements.

Abstract: A hybrid bearing cage, suitable for high-speed applications, includes a plastic ring and a metal stiffener. Rollers, such as balls, are retained in roller retainers in the plastic ring. The roller retainers are joined by links. The metal stiffener has an annular portion and a plurality of radial extensions that extend over the links, reducing deflection and stress concentrations in the plastic ring due to centrifugal forces.

Abstract: The invention relates to a rolling element bearing cage formed of one or more segments, each segment comprising: a supporting frame having a plurality of spaced apart openings each for accommodating a rolling element; and a reinforcing frame, inserted within the supporting frame, having a corresponding plurality of openings each for aligning with the openings of the supporting frame.

Abstract: Provided are that a cage for a rolling bearing in which seizure or break is not generated under a condition of a high temperature and a high speed in which a dm·n value is not less than 80×104, and a rolling bearing using the cage. The rolling bearing 1 is provided with an inner ring 2, an outer ring 3, a plurality of rolling elements 4 interposed between the inner ring and the outer ring and a cage 5 which retains the rolling elements 4. The cage 5 is formed by injection molding a resin composition. The resin composition comprises polyamide resin made from a dicarboxylic acid component and a diamine component as a base resin and a fiber reinforcing member added. The dicarboxylic acid component contains terephthalic acid as a main component. The diamine component contains 1,10-diaminodecane as a main component. The fiber reinforcing member contains 15 to 50 mass % of glass fibers or 10 to 35 mass % of carbon fibers based on the whole resin composition.

Abstract: The invention relates to a rolling element bearing cage formed of one or more segments, each segment comprising: a supporting frame having a plurality of spaced apart openings each for accommodating a rolling element; and a reinforcing frame, inserted within the supporting frame, having a corresponding plurality of openings each for aligning with the openings of the supporting frame.

Abstract: A roller bearing cage, in particular for use with insufficient lubrication, including a plastic base body (2), a modified surface (4) of the base body (2), and a metallic coating (3) on the modified surface (4) of the base body (2).

Abstract: A steel sheet for electroplating includes, by mass %, C: 0.0005% to 0.0050%, Si: 0.20% to 1.0%, Mn: 0.40% to 2.5%, P: 0.05% or less, Ti: 0.010% to 0.050%, Nb: 0.010% to 0.040%, B: 0.0005% to 0.0030%, S: 0.02% or less, Al: 0.01% to 0.30%, N: 0.0010% to 0.01%, and the balance including Fe and impurities, in which when Si content is represented by [Si] and Mn content is represented by [Mn], “[Mn]+5[Si]” is 2.0 to 7.0, and the steel sheet has surface property in which an average of displacements of a measurement point obtained based on a moving average of continuous 31 points in total including 15 front points and 15 back points in a cross-sectional profile of a surface obtained by measuring the average of displacements in an evaluation length of 10 ?m or more at an interval of 0.07 ?m, is 0.005 ?m to 0.10 ?m.

Abstract: The present invention relates to a cage for a rolling bearing, in particular for a ball bearing, to a rolling bearing with a cage and to the use of a cage in a high-speed rolling bearing with a characteristic speed value n×dm>1,000,000 mm/min, in particular for industrial spindle-bearing applications and in the medical sector, in particular in dental technology.

Abstract: A cage includes: an annular body having pocket holes for receiving balls; and a resin portion formed through injection molding of a resin containing a solid lubricant with the body being set as an insert component. The resin portion includes: first parts formed along inner peripheral surfaces of the pocket holes of the body to form pocket surfaces to be held in sliding contact respectively with the balls; and a second part formed along an outer peripheral surface (or inner peripheral surface) of the body to form a guide surface to be held in sliding contact with an outer ring (or inner ring). The first parts and the second part are formed integrally with each other. Weld lines of the resin portion are formed at positions of avoiding exposure of the weld lines at both end portions of the pocket surfaces in a cage circumferential direction.

Abstract: A separator 8 including a solid lubricant is disposed between adjacent rolling elements 7. Relative movement of the adjacent rolling elements 7 and the separator 8 in a direction of separating apart in a circumferential direction is restricted by restricting members 10, and the restricting members 10 are disposed at plural locations in the circumferential direction. A minute gap ? is provided between the adjacent restricting members 10, to allow relative movement therebetween. This can provide a solid-lubrication rolling bearing capable of stably preventing rotational locking and unintended disassembling of the bearing for a long period.

Abstract: An exhaust gas turbocharger (1) with a compressor (2) which has a compressor wheel (3) arranged in a compressor housing (4); with a turbine (5) which has a turbine wheel (6) arranged in a turbine housing (7); and with a bearing housing (8) which is arranged between the compressor housing (4) and turbine housing (7); and which has a bearing (9) for a rotor shaft (10) which bears the turbine wheel (6) and the compressor wheel (3), wherein the bearing (9) has at least one ceramic insert (11, 12) which is on the bearing housing side and is under compressive prestress, and at least one ceramic insert (11, 12) which is on the motor shaft side and is under tensile prestress.

Abstract: Provided is a practical rolling element accommodating tool that engages firmly with a reinforcing material without compromising flexibility, wherein tension strength of the reinforcing material is sufficiently exhibited.

Abstract: A cage for a rolling bearing is coupled to a rolling bearing including an inner ring, an outer ring and a plurality of rolling elements rolling between the inner ring and the outer ring to keep intervals of the plurality of rolling elements, wherein the plurality of rolling elements include bodies coupled along a circumference thereof at predetermined intervals, wherein each of the bodies includes a first piece and a second piece which are attachable to each other and detachable from each other. A first coupler and a second coupler configured to be capable of being coupled to each other are respectively formed at the first piece and the second piece, and the first piece and the second piece are primarily coupled by means of a coupling force of the first coupler and the second coupler.

Abstract: A ball bearing has an outer race and an inner race A plurality of ball members are supported radially between the inner and outer races. A pair of bearing cage halves are placed at axial ends of the balls. The bearing cage halves are formed of a first relatively hard material, and have a plating of a softer material on some surfaces The bearing cage halves have pockets facing the balls and with the soft plating The bearing cage halves are riveted together along a contact surface, not including the soft plating. The rivets extend through an aperture in each of the bearing cage halves, not provided with the soft plating. The rivets have heads extending into a ditch, not provided with the soft plating. A rotor sub-assembly, a generator, and a method of maintaining a generator are also disclosed.

Abstract: A rolling bearing which is capable of preventing the rolling elements from dropping out from between the inner and the outer rings even when the separators have been worn to an advanced stage. A rolling bearing includes: a plurality of rolling elements arranged between an inner and an outer rings; and a plurality of prismatic separators disposed in a circumferential direction between the rolling elements. The separator includes integrally therewith a metal band on at least one of its outer surfaces including those which face the inner or the outer ring, or at least one of its axial side surfaces, excluding however, surfaces which face the circumferential direction and make contact with the rolling elements. The metal band has a narrower width than a width of the separator in the circumferential direction, and prevents wear of the separator from advancing beyond a certain extent.

Abstract: A rolling element guide cage having a ring element which is made from a sheet material and has an axial profiling produced using forming techniques and forms a plurality of successive rolling element guide structures in the circumferential direction. The ring element is composed of at least two flat material ring segments joined to one another successively in the circumferential direction, said segments being joined together in a manufacturing step which precedes the formation of the axial profiling.

Abstract: Each pipe member has a plurality of slits located at intervals in the circumferential direction of the pipe member, extending in the axial direction of the pipe member, and extending through the pipe member in the radial direction of the pipe member. The pipe members are passed through through-holes of the first annular member and through-holes of the second annular member aligned with the through-holes of the first annular member. After shaft portions of rivets are passed through the pipe members, opposite end portions of each rivet are swaged to compress the pipe member in its axial direction to expand the pipe member in its radial direction. Thus, the pipe members are pressed to the inner peripheral faces that define the through-holes of the first and second annular members.

Abstract: A rolling element guide for a bearing assembly comprising of a steel or other metal skeleton overmolded with a plastic material.

Abstract: It is an object of the present invention to provide a resin composition whose flowability is secured when the resin composition is injection-molded into injection-molded articles such as a resin-made crown-shaped cage and a resin-made seal both for a rolling bearing and a resin-made sliding bearing and which is capable of enhancing the mechanical strengths and toughnesses of these injection-molded articles to such an extent that these injection-molded articles can be used as bearing members. The resin composition is formed into a molded article and used as a bearing member. The resin composition is composed of polyamide resin or polyester resin to which polycarbodiimide is added. The polyamide resin is at least one resin selected from among polyamide 66 resin and polyamide 11 resin. The polyester resin is polytrimethylene terephthalate resin. 0.5 to 6 wt % of the polycarbodiimide is contained in an entirety of the resin composition.

Abstract: A process for producing a graphite cage for an anti-friction bearing, which cage holds a plurality of anti-friction elements. A cage injection molding is injected in an injection molding process from a mass which contains carbon mesophase powder, and this cage injection molding is subsequently heat-treated in order to transform the carbon from the mesophase into pure graphite.

Abstract: A tape-shaped product and a belt for a ball chain are provided. A tape-shaped product of synthetic resin includes a tape of a thermoplastic resin, and a preliminarily stretched fibrous member of a thermoplastic resin contained therein along longitudinally parallel edges or in proximity thereto of the tape. A belt for a ball chain, includes a tape-shaped product of synthetic resin formed by injection molding, together with a fibrous member as an insert of a resin of the same kind as that of the fibrous member so that the fibrous member is disposed along the longitudinal edges or in proximity thereto, ball-insetting holes are disposed at equal intervals, and ball-retaining projections are disposed around the holes.

Abstract: A retainer of synthetic resin is provided in such a way that abnormal heat generation in a bearing and wear of the retainer due to interference between the retainer and balls are less likely to arise while the bearing is rotating at a high speed. A retainer (5) of synthetic resin includes two annular members (10) made of synthetic resin and facing each other in the axial direction, the annular members defining therebetween a plurality of circumferentially spaced apart pockets (11) in which respective balls (4) are received. Concave spherical surfaces (23) are formed at the circumferential ends of the respective pockets (11) so as to extend along the outer peripheries of the balls (4), and cylindrical surfaces (22) are formed at the axial ends of the respective pockets (11).

Abstract: The present invention provides a member, for a resin-made rolling bearing, which has a low extent of a moisture absorption-caused change in its dimension and mechanical properties, keeps sufficiently high mechanical properties after the member absorbs moisture, and is excellent in its resistance to hydrolysis, grease deterioration, and heat and also provides the rolling bearing in which the member for the rolling bearing is used. A rolling bearing (7) has an inner ring (8), an outer ring (9), a plurality of rolling elements (10) interposed between the inner ring (8) and the outer ring (9), a crown-shaped cage (11) for retaining the rolling elements (10), and a seal (12) covering an opening disposed at a gap between the inner ring (8) and the outer ring (9). The cage (11) and the seal (12) are moldings of a resin composed of polyphthalamide resin.

Abstract: A ball bearing has an outer race and an inner race A plurality of ball members are supported radially between the inner and outer races. A pair of bearing cage halves are placed at axial ends of the balls. The bearing cage halves are formed of a first relatively hard material, and have a plating of a softer material on some surfaces The bearing cage halves have pockets facing the balls and with the soft plating The bearing cage halves are riveted together along a contact surface, not including the soft plating. The rivets extend through an aperture in each of the bearing cage halves, not provided with the soft plating. The rivets have heads extending into a ditch, not provided with the soft plating. A rotor sub-assembly, a generator, and a method of maintaining a generator are also disclosed.

Abstract: Disclosed is a bearing component having at least one layer having a high hardness and a high current insulation property, the layer comprising a nonconductive oxide layer selected from the group comprising an Al2O3 layer, a TaO layer, an SiO2 layer, a mixed layer comprising two or more of the foregoing oxides, a multilayer structure comprising alternating layers of two or more of the foregoing oxides and a DLC layer such as a ta-C layer, there being at least one ALD layer comprising at least one layer of a material deposited by an ALD (atomic layer deposition) process on the at least one layer having a high hardness and a high current insulation property, the ALD layer itself having a high current insulation property and comprising a material or layer structure selected from the said group of materials.

Abstract: A cage has a ring portion, and a plurality of column portions that protrude from the ring portion, that are arranged in the circumference direction. Each column portion has a column portion radially inward section that forms a bearing-radial-direction inward side portion, and a column portion radially outward section that is connected to the radially inward section at its radially outer end position, so as to protrude on both sides in the circumferential direction from the radially inward section. A connection position at which the radially outward section is connected to the radially inward section is adjusted to a position radially outward of a pitch circle position of the plurality of the balls that are held in the respective pockets. Thus, the thickness of the radially inward section at the connection position is larger than the thickness of the radially inward section at the pitch circle position.

Abstract: In the cage, on opposing edges of an outer circumferential opening of each of some of cage pockets, guiding faces for limiting the inward displacement in the radial direction of each of balls for a pitch circle diameter are provided; and on opposing edges of the inner circumferential opening of each of remaining cage pockets, guiding faces for limiting the outward displacement in the radial direction of each of the balls for the pitch circle diameter are provided, thereby making a ball guide.

Abstract: A ball bearing cage with an annular rolling element retaining body, which has ball sockets distributed around a circumference of the rolling element retaining body for receiving spherical rolling elements. The ball sockets are distributed around the circumference, such that distances between two adjacent ball sockets increase in a circumferential direction, starting at a smallest distance between two adjacent sockets at least in a circumferential sector.

Abstract: The metallic mold 90 includes a product configuration portion 93 formed between an upper mold 91 and a lower mold 92. This product configuration portion 93 is composed so that a rolling element accommodating belt 50 formed by this product configuration portion 93 can include spacer portions interposed between balls adjacent to each other in an infinite circulating passage and also include connecting arm portions for connecting the spacer portions to each other and so that the balls can be aligned in the alignment direction in the infinite circulating passage. The upper mold 91 has a splitting structure. In this splitting structure, a splitting position BL is set at a position passing through a position 91t for forming an end portion on the outer circumferential side in the inner and outer circumferential direction of the infinite circulating passage of the spacer portions 51.

Abstract: A cage is made of a magnesium alloy, the magnesium alloy being molded by means of injection molding using a mold including a cavity portion having a shape corresponding to a shape of the cage, and has a shape resulting from being forcedly extracted from the mold. As a result, a cage made of a magnesium alloy of high strength and having a shape resulting from being forcedly extracted from a mold, a rolling bearing including the cage, a machine tool including the rolling bearing, and a method of manufacturing the cage can be provided.

Abstract: A method and apparatus is disclosed whereby there is an improvement in the construction of the housing for the balls of a bearing. The benefit of this method of construction is that under certain loading forces, the ball cage, now termed a retaining disk, does not bind the balls. The retaining disk is designed with an elliptical hole that spaces the balls apart but allows them enough freedom to rotate without any binding. More concisely, the ball bearing includes an inner race and an outer race with a plurality of bearing balls movably retained therebetween. A split retaining ring, having upper and lower annular rings, forms a plurality of bearing ball housings. These ball housings include a substantially spherical cavity which is elongated in an arc, or a short linear path, about a rotational center line of the ball bearing.

Abstract: According to the invention, a cage has a ring portion, and a plurality of column portions that protrude from the ring portion, are arranged in the circumference direction, and form pockets that house balls serving as rolling elements. Each column portion has a column portion radially inward section that forms a bearing-radial-direction inward side portion of the column portion, and a column portion radially outward section that is connected to the column portion radially inward section at its radially outer end position, so as to protrude on both sides in the circumferential direction from the column portion radially inward section. An inner surface of each pocket is formed in a spherical shape that lies astride the column portion radially inward section and the column portion radially outward section.

Abstract: A retainer made of a synthetic resin for use in a deep groove ball bearing is proposed of which the lubricity has been improved. The retainer includes a cylindrical first split retainer member (41) having a first axial side, and a cylindrical second split retainer member (42) having a second axial side coupled to the first axial side of the first split retainer member (41). Circumferentially spaced apart first and second cutouts (45 and 50) are formed in the first axial side of the first split retainer member (41) and the second axial side of the second split retainer member (42), respectively, which define respective pockets for receiving balls with the split retainers (41 and 42) coupled together.

Abstract: It is an object of the present invention to provide a cage that can be used in a cryogenic-temperature environment or a vacuum without providing the cage with a complicated construction and without performing special treatment and a bearing using the cage. A cage made of resin has an annular main body having a plurality of pocket portions radially penetrating the main body; and a plurality of pocket members, provided on the annular main body, which hold rolling elements of a rolling bearing. The main body is a molding of a first resin composition consisting of a first resin and a solid lubricant mixed therewith; and at least a rolling element-retaining surface of each of the pocket members is made of a second resin composition containing fluorocarbon resin as a main component thereof. The molding of the first resin composition has a tensile strength of not less than 30 MPa and a heat-resistant temperature of not less than 200° C. The second resin composition is a fluorocarbon resin composition.

Abstract: It is a cage that is formed of a resin and that holds balls serving as rolling elements. The cage includes an annular base portion, and a plurality of claw portions that are formed to be arranged at constant intervals on the circumference of the base portion and to protrude therefrom. A pocket for accommodating the ball is formed between each pair of adjacent ones of the claw portions. In the resin cage for a ball bearing, thinning recesses are formed in end parts 11a of the claw portions and a rear surface of the base portion, respectively.

Abstract: A thin-wall bearing, comprising a retainer (4) formed in a divided type having a plurality of resin plate-like members (5), (5), . . . curved along an inner ring (1) and an outer ring (2). The retainer (4) comprises pockets (6) opening to the axial end part thereof and rollingly holding balls (3). Slit-like through holes (14) extending in the axial direction and opening to the axial end part where the opening parts (7) of the pockets (6) are positioned are formed at the center parts of pillars (10) between the pockets (6) and (6) adjacent to each other. As a result, the thin-wall bearing can have excellent lubricity.

Abstract: A retainer for a rolling bearing, which is used for a food machine or a vacuum apparatus, containing an increased amount of a lubricating oil and enhancing a use efficiency of the lubricating oil and rolling bearing is described. The retainer consists of a molding, of a synthetic resin composition, which holds a rolling element of a rolling bearing. The molding is composed of a resinous porous article having an interconnected hole porosity not less than 30% and a lubricating oil which impregnates the resinous porous article. The resinous porous article has an interconnected hole are formed by molding a resin containing a pore-forming substance having a melting point higher than that of the resin and can be used as a food material, and by extracting said pore-forming substance from the molding with a solvent which dissolves the pore-forming substance and does not dissolve the resin.

Abstract: The present invention provides a porous resinous oil-retaining article, containing lubricating oil, which is excellent in the utilization efficiency of the lubricating oil, has a high mechanical strength, and further allows the resin and the lubricating oil to be combined with each other according to a use and a specification. The present invention also provides a method of producing the resinous oil-retaining article. The resinous oil-retaining article comprises a resinous porous article having interconnected holes which are open to a surface of the resinous porous article; and an oil impregnated into the resinous porous article. The interconnected holes are formed by molding a resin containing a pore-forming substance into a molding and extracting a part of the pore-forming substance from the molding with a solvent which dissolves the pore-forming substance and does not dissolve the resin. An interconnected hole porosity of the resinous porous article is not more than 30%.

Abstract: The present invention provides a rolling bearing which does not contain a hazardous substance and thus does not pollute environment. The present invention also provides a retainer, for holding rolling elements of the rolling bearing, which is made of a cold rolled steel plate. The retainer is subjected to at least one kind of surface treatment selected from among electrogalvanizing, electrotinning, electrolytic tin-zinc alloy plating, electrolytic zinc-iron alloy plating, and electrolytic zinc-nickel alloy plating. The retainer is further chromated with trivalent chromium. The rolling bearing uses the retainer for the rolling bearing.

Abstract: It is an object of the present invention to provide an injection-molded article such as a resin-made cage, a resin-made seal, a resin-made sliding bearing, and a resin-made gear having reliable flowability, enhanced mechanical strength and toughness, and improved wear resistance. A resin composition is composed of a biodegradable polyester polymer particularly polybutylene succinate to which not less than 10 wt % nor more than 40 wt % of a fibrous inorganic reinforcing material and not less than 0.5 wt % nor more than 10 wt % of polycarbodiimide resin are added. The injection-molded article is obtained by injection molding the resin composition.

Abstract: A multilayer film 21 is formed by layering layers whose adjoining layers are made of mutually different metals or alloys by an electroplating process on a surface of a metallic annular main body part 20 that has a pocket to accommodate a ball by holding the ball from both sides in the axial direction.

Abstract: The present invention provides a resinous porous article having a high interconnected hole porosity and capable of retaining a large amount of a lubricating oil and does not rust iron and steel, even though an unextracted portion of a pore-forming substance bleeds out when the resinous porous article is used as parts which contact a metal portion or the like and a method of producing the resinous porous article. The resinous porous article is formed by a producing method of molding a resin containing the pore-forming substance into a molding, and extracting the pore-forming substance from the molding with a solvent which does not dissolve the resin therein. The resinous porous article has an interconnected hole porosity not less than 30%. The pore-forming substance consists of an alkali compound.

Abstract: A bearing assembly (20) for use in a medical, surgical, or dental handpiece (10) that enables spindle rotation for a supported rotary tool (36) at high speeds. The bearing assembly (28) incorporates annular gap shields (50, 54) at each axial end to prevent contaminate ingress and to retain lubricating grease within the bearing assembly (28) to avoid re-lubricated after each use or sterilization cycle.

Abstract: Double row angular contact ball bearing (10) has split inner rings (18, 24) and two plastic comb snap cages (32, 44). The comb cage has retaining tabs (38, 50) which mate with retaining grooves (22, 28) in the split inner rings. These retaining tabs hold the inner rings into the bearing.

Abstract: A retainer for a rolling bearing, which is used for a food machine or a vacuum apparatus, containing an increased amount of a lubricating oil and enhancing a use efficiency of the lubricating oil and rolling bearing is described. The retainer consists of a molding, of a synthetic resin composition, which holds a rolling element of a rolling bearing. The molding is composed of a resinous porous article having an interconnected hole porosity not less than 30% and a lubricating oil which impregnates the resinous porous article. The resinous porous article has an interconnected hole are formed by molding a resin containing a pore-forming substance having a melting point higher than that of the resin and can be used as a food material, and by extracting said pore-forming substance from the molding with a solvent which dissolves the pore-forming substance and does not dissolve the resin.

Abstract: A rolling bearing includes an inner ring having an outer surface, an outer ring having an inner surface, a plurality of rolling elements rotatably disposed between the inner ring and the outer ring, and a retainer for retaining the rolling elements. The retainer is made of a resin material and is positioned with respect to the inner surface of the outer ring or the outer surface of the inner ring. The retainer includes a pair of annular portions axially arranged in parallel and a columnar portion coupling the annular portions. Then, the rolling bearing satisfies the following expression: AI=LH3/dm?0.025 LH3/dm2?0.025 mm2 in which H is a radial length of a section of the annular portion, L is an axial length of the same, and dm is PCD of the rolling element.