A bearing includes an inner raceway and an outer raceway extending about a rotational axis. The outer raceway is spaced radially from the inner raceway such that an annular cavity is defined between the inner raceway and the outer raceway. The bearing also includes a plurality of first rollers disposed in the annular cavity. Each first roller of the plurality of first rollers includes a first end, a second end spaced axially from the first end, and a first surface extending between the first end and the second end. A first profile drop extends between the first end and the first surface. A second profile drop extends between the second end and the first surface. The second profile drop differs from the first profile drop. The bearing further includes a plurality of second rollers disposed in the annular cavity and spaced axially from the plurality of first rollers.

A generatrix shape to which crowning is applied includes a first generatrix shape which is formed in a central portion in an axial direction of at least one of an outer ring raceway surface, an inner ring raceway surface, and a rolling surface of a roller and is composed of a straight line, a pair of second generatrix shapes which are formed from both ends in the axial direction toward the outside in the axial direction of the first generatrix shape and are composed of a single arc curve, and a pair of third generatrix shapes which are formed from both ends in the axial direction toward the outside in the axial direction of the second generatrix shape and are composed of a composite curve of a single arc curve and a logarithmic curve.

Embodiments of the invention relate to methods of fabricating leached polycrystalline diamond compacts (PDCs) in which a polycrystalline diamond table thereof is leached and resized to provide a leached region having a selected geometry. Creating a leached region having such a selected geometry may improve the performance of the PDC in various conditions, such as impact strength and/or thermal stability.

A raceway surface (3a) of an outer ring (3) of a tapered roller bearing (1) includes a composite crowning surface. The composite crowning surface includes a center curve (3a1), which is formed at a center portion in a generating-line direction, and end portion curves (3a2 and 3a3), which are formed on both sides of the center curve (3a1) in the generating-line direction. The raceway surface (3a) of the outer ring (3) is entirely subjected to superfinishing. Each of a ratio (R.sub.2/R.sub.1) of a curvature radius (R.sub.2) of the end portion curve (3a2) to a curvature radius (R.sub.1) of the center curve (3a1) and a ratio (R.sub.3/R.sub.1) of a curvature radius (R.sub.3) of the end portion curve (3a3) to the curvature radius (R.sub.1) is set to 0.02 or more. Each of drop amounts of the end portion curves (3a2 and 3a3) is set to 0.07 mm or less.

A retainer of a tapered roller bearing includes crossbars having guide surfaces which circumferentially contact the tapered rollers, and formed with first recessed surfaces and second recessed surfaces which are both in the form of cutouts circumferentially recessed from the respective guide surfaces, to reduce stirring resistance and shear resistance of oil. To reduce the contact lengths between the rolling surface central portions of the tapered rollers and the guide surfaces, the guide surfaces are smoothly convex in the longitudinal direction of the tapered rollers.

A linear motion guide unit prevents damage to a corner portion of an end surface of a carriage resulting from high-speed rolling of rollers, and eliminates the need for strict dimensional management of facing end surfaces of the carriage and a spacer. A crowning is formed at an end portion of the carriage, and an R chamfered portion is formed at a corner of an end surface of the carriage. An R chamfered portion is formed at a corner of the end surface of the spacer. The R chamfered portions define a valley portion between the facing surfaces of the carriage and the spacer. The rollers roll above the valley portion while striding it to thereby be prevented from colliding against the corner portion of the end surface of the carriage, whereby damage to the corner portion of the end surface of the carriage can be prevented.

The present invention relates to a pressure roller bearing for a pallet car of a pelletizing machine. The bearing includes an external annular race having: an exterior surface for reversible mating engagement with a tooth gap of a wheel, a pair of sidewalls defining ends of the bearing, wherein the radial diameter of the exterior surface at a center portion in the axial direction is greater than the radial diameter of the exterior surface at the ends of the bearing, and an interior annular groove; an internal annular race defining a hole therethrough for receiving an axle, and having an exterior annular groove; and a plurality of rolling cylindrical members located in an interior space defined by the interior annular groove and the exterior annular groove when the internal annular race is received by the external annular race.

A roller bearing includes an inner ring having an inner-ring raceway surface on an outer periphery of the inner ring, an outer ring arranged concentric with and peripherally outside the inner ring and having, on an inner periphery of the outer ring, an outer-ring raceway surface that faces the inner-ring raceway surface, a plurality of rollers interposed between the inner-ring raceway surface and the outer-ring raceway surface in a rollable manner, and a cage that holds the rollers at predetermined intervals along a circumferential direction. Opposite end portions of the outer-ring raceway surface in an axial direction serve as guide surfaces or which rotation of the cage is guided. Or an outer periphery of the cage, slidable contact surfaces are formed which slidably contact the guide surfaces and which are arranged to face the respective guide surfaces across a labyrinth clearance.

In a linear motion guide unit, in order to prevent direct collision of a roller, or a rolling element, with an end portion of a carriage, an extending portion of a spacer of an end cap is disposed at the end portion of the carriage for absorbing impact resulting from collision of the roller. The spacer has the extending portion which protrudes from the spacer at a position adjacent to an inner circumferential surface of a turnaround passage and which has a wall surface continuous from the inner circumferential surface of the turnaround passage. The wall surface of the extending portion serves as a collision receiving surface for receiving a colliding roller. The carriage has a housing recess which is formed at an end of a raceway groove thereof and to which the extending portion is fitted.

A ball bearing not allowing locations where the surface pressure becomes locally higher at a race at the time of a high load and thereby keeping cracking from occurring and in turn realizing a longer lifespan is provided. A pair of races (12, 14) and at least one rolling element (16) movably clamped between the pair of races move are provided. A cross-sectional profile line (14a) of a part of each of the pair of races contacting the rolling element has the smallest radius of curvature at a position (P) sticking out the most in the first direction (D1) over which the pair of races face. The cross-sectional profile line becomes larger in radius of curvature the further from the position (P) in a second direction (D2) vertical to the first direction (D1) in the cross-section. The cross-sectional profile line is comprised of a single function. When a midpoint of the profile line in the second direction is the origin, an axis extending in the second direction is the X-axis and the axis extending in the first direction is the Y-axis, and a radius of the rolling element is (R), the cross-sectional profile line satisfies equation (1):

X.sup.2/{2R(1+0.05)}<Y<X.sup.2/{2R(10.05)}(1)