A multilayer circular grinding wheel includes at least three substantially planar layers including an inner layer and two outer layers immediately adjacent to the inner layer, of which at least the inner layer has a proportion of diamond abrasive grit, the proportion of diamond in the abrasive grit being greater in the inner layer than in the outer layers.

A spherical object cleaning system includes a cleaning apparatus for cleaning a spherical object. This cleaning apparatus includes a first member having a first surface, and a second member having a second surface facing the first surface. The first surface and the second surface are sandwiching surfaces sandwiching the spherical object. The first surface and the second surface are configured to be rotatable relative to each other. This cleaning apparatus further includes an introduction portion configured to introduce the spherical object into a space between the first surface and the second surface, and a discharge portion configured to discharge the spherical object from the space. One of the first surface and the second surface is provided with a spiral groove configured to guide the spherical object from the introduction portion to the discharge portion.

An apparatus for imparting compressive residual stress to at least a surface portion of a first plurality of balls includes a first body having a first surface, the first surface including a smooth contact portion, the smooth contact portion being substantially flat or convex and having a surface hardness greater than or equal to the initial surface hardness of the balls. The apparatus also includes a second body having a second surface, the first surface overlying the second surface, and at least one drive operably connected to the first body or to the second body and configured to move one of the first and second bodies relative to the other body at a substantially fixed distance, the at least one drive also being configured to move the first body toward the second body with a force or to move the second body toward the first body with the force.

A spherical object cleaning system includes a cleaning apparatus for cleaning a spherical object. This cleaning apparatus includes a first member having a first surface, and a second member having a second surface facing the first surface. The first surface and the second surface are sandwiching surfaces sandwiching the spherical object. The first surface and the second surface are configured to be rotatable relative to each other. This cleaning apparatus further includes an introduction portion configured to introduce the spherical object into a space between the first surface and the second surface, and a discharge portion configured to discharge the spherical object from the space. One of the first surface and the second surface is provided with a spiral groove configured to guide the spherical object from the introduction portion to the discharge portion.

A sphere size measuring unit (15) measures respective diameters of an object sphere in the course of processing and a standard sphere made of the same material as that of the object sphere and furthermore having a target diameter of the object sphere. A size difference calculation unit (161) calculates a size difference between the diameter of the object sphere and the diameter of the standard sphere. A determination unit (162) compares the obtained size difference with a threshold value so as to determine whether or not the diameter of the object sphere reaches the target value.

A sphere size measuring unit (15) measures respective diameters of an object sphere in the course of processing and a standard sphere made of the same material as that of the object sphere and furthermore having a target diameter of the object sphere. A size difference calculation unit (161) calculates a size difference between the diameter of the object sphere and the diameter of the standard sphere. A determination unit (162) compares the obtained size difference with a threshold value so as to determine whether or not the diameter of the object sphere reaches the target value.

A sphere size measuring unit (15) measures respective diameters of an object sphere in the course of processing and a standard sphere made of the same material as that of the object sphere and furthermore having a target diameter of the object sphere. A size difference calculation unit (161) calculates a size difference between the diameter of the object sphere and the diameter of the standard sphere. A determination unit (162) compares the obtained size difference with a threshold value so as to determine whether or not the diameter of the object sphere reaches the target value.

A sphere size measuring unit (15) measures respective diameters of an object sphere in the course of processing and a standard sphere made of the same material as that of the object sphere and furthermore having a target diameter of the object sphere. A size difference calculation unit (161) calculates a size difference between the diameter of the object sphere and the diameter of the standard sphere. A determination unit (162) compares the obtained size difference with a threshold value so as to determine whether or not the diameter of the object sphere reaches the target value.

The present invention relates to a method and an arrangement for grinding spherical products (12), such as e.g. bowling balls, in particular. Such an arrangement comprises at least one grinding machine (1) having a spherically oscillating grinding movement. A fastening plate (6) fitted on the grinding machine has a spherically shaped bearing surface (7) and a grinding product (9) fitted on this, which through its slits (13) adopts a position with accuracy of shape on the spherically shaped surface. The grinding product (9) will form a contact surface (17) in the interface, in which the grinding product cooperates with the spherical product. This contact surface then adopts a radius of curvature arranged to substantially correspond to the radius (r) of the spherical product (12). The grinding is performed with a spherically oscillating grinding movement, which is adapted to the radius of the spherical product and simultaneously coincides with the radius of curvature of the contact surface.

The present invention relates to a method and an arrangement for grinding spherical products (12), such as e.g. bowling balls, in particular. Such an arrangement comprises at least one grinding machine (1) having a spherically oscillating grinding movement. A fastening plate (6) fitted on the grinding machine has a spherically shaped bearing surface (7) and a grinding product (9) fitted on this, which through its slits (13) adopts a position with accuracy of shape on the spherically shaped surface. The grinding product (9) will form a contact surface (17) in the interface, in which the grinding product cooperates with the spherical product. This contact surface then adopts a radius of curvature arranged to substantially correspond to the radius (r) of the spherical product (12). The grinding is performed with a spherically oscillating grinding movement, which is adapted to the radius of the spherical product and simultaneously coincides with the radius of curvature of the contact surface.