A rotation mechanism includes a shaft portion, a bearing portion, a protruding portion, and a stopper. The bearing portion configured to rotate with respect to a predetermined axis as a center of rotation and configured to slide relative to an outer periphery of the shaft portion. The protruding portion protrudes from the shaft portion. The stopper is integrally formed the bearing portion. The stopper faces the protruding portion. A length of the protruding portion in a direction in which the protruding portion protrudes is larger than a distance from the center of rotation to a sliding portion where the bearing portion slides relative to the outer periphery of the shaft portion.

A key assembly includes a capstan and a key. The key includes an upper surface, a hole part having a first inner side surface supporting the capstan, and an opening part arranged between the upper surface and the hole part, the opening part having a second inner side surface surrounding the capstan.

A key assembly includes a capstan and a key. The key includes an upper surface, a hole part having a first inner side surface supporting the capstan, and an opening part arranged between the upper surface and the hole part, the opening part having a second inner side surface surrounding the capstan.

The present disclosure relates to a piano-action. The piano-action may comprises a first moving component including a concavity structure, a second moving component including a convexity structure, wherein the convexity structure and the concavity structure are configured to match each other and capable of being clipped together, and a third moving component being thin and flexible and configured to fixedly fit between the first moving component and the second moving component when the convexity structure of the second moving component is clipped into the concavity structure of the first moving component.

The present disclosure relates to a piano-action. The piano-action may comprises a first moving component including a concavity structure, a second moving component including a convexity structure, wherein the convexity structure and the concavity structure are configured to match each other and capable of being clipped together, and a third moving component being thin and flexible and configured to fixedly fit between the first moving component and the second moving component when the convexity structure of the second moving component is clipped into the concavity structure of the first moving component.

According to an embodiment of the present invention, a keyboard apparatus includes a key, a frame, and a connecting portion having a first flexible portion, a second flexible portion serially connected to the first flexible portion between the key and the frame, and a connector for connecting the first flexible portion and the second flexible portion to each other attachably and detachably, the connecting portion turnably connecting the key to the frame by utilizing flexibility of the first flexible portion or the second flexible portion.

A hammer assembly includes: a pivot member that pivots about a pivot axis; and a weight supported by the pivot member and including a plate portion. The plate portion has a first surface and a second surface opposite to the first surface. The plate portion has: a first region with a thickness defined by a length between the first surface and the second surface in a pivot-axis direction at a portion farthest from the pivot axis; and a second region with a thickness greater than that in the first region. In a case where the areas of the first region and the second region on a projected plane when the first region and the second region are viewed in the pivot-axis direction are compared with each other, the area of the first region is less than the area of the second region.

A fastening structure for fastening a to-be-fastened component to a wooden component by using a screw, wherein the wooden component is made of wood having a specific gravity of 0.08 g/cm.sup.3 to 0.85 g/cm.sup.3 inclusive, the screw has a nominal diameter of 0.8 mm to 3.5 mm inclusive, and the distance between a neutral position in a longitudinal direction of an effective screw part, which is the portion where the wooden component and a male screw part formed in a shaft part of the screw mesh together, and the surface of the wooden component that comes into contact with the to-be-fastened component is 1 mm to 15 mm inclusive.

A fastening structure for fastening a to-be-fastened component to a wooden component by using a screw, wherein the wooden component is made of wood having a specific gravity of 0.08 g/cm.sup.3 to 0.85 g/cm.sup.3 inclusive, the screw has a nominal diameter of 0.8 mm to 3.5 mm inclusive, and the distance between a neutral position in a longitudinal direction of an effective screw part, which is the portion where the wooden component and a male screw part formed in a shaft part of the screw mesh together, and the surface of the wooden component that comes into contact with the to-be-fastened component is 1 mm to 15 mm inclusive.

A hammer assembly includes: a pivot member that pivots about a pivot axis; and a weight supported by the pivot member and including a plate portion. The plate portion has a first surface and a second surface opposite to the first surface. The plate portion has: a first region with a thickness defined by a length between the first surface and the second surface in a pivot-axis direction at a portion farthest from the pivot axis; and a second region with a thickness greater than that in the first region. In a case where the areas of the first region and the second region on a projected plane when the first region and the second region are viewed in the pivot-axis direction are compared with each other, the area of the first region is less than the area of the second region.