| CPC B23C 5/109 (2013.01) [B23C 5/202 (2013.01); B23C 2200/0411 (2013.01); B23C 2200/28 (2013.01)] | 20 Claims | 

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               1. A cutting insert, comprising: 
            an upper surface having a polygonal shape comprising a long side and a short side; 
                a lower surface located on a side opposite to the upper surface; 
                a lateral surface located between the upper surface and the lower surface; 
                a through hole that opens into a center of the upper surface and a center of the lower surface; and 
                a cutting edge located on the short side, wherein 
                the lateral surface comprises a first lateral surface that is located along the long side and has an outwardly protruded shape in a top view, 
                the first lateral surface comprises 
                a first surface that is overlapped with a central axis of the through hole in a side view of the first lateral surface and is parallel to the central axis, 
                  a second surface that is located closer to the short side than the first surface and is parallel to the central axis, 
                  a third surface that is located more away from the short side than the first surface and is parallel to the central axis, and 
                  a first inclined surface that is located between the second surface and the upper surface, and is inclined toward the central axis as the first inclined surface extending toward the long side, 
                the first inclined surface is spaced from the first surface, and 
                the first inclined surface comprises a region having an inclination angle relative to the central axis, the inclination angle becoming smaller as the first inclined surface extending toward the first surface. 
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