Reversible square cutting insert and rotary cutting tool

In a cutting tool rotatable about a tool axis, a reversible cutting insert is removably secured in a tool body. The cutting insert has opposing top and bottom end surfaces interconnected by a peripheral surface, and a mid-plane located therebetween. The peripheral surface includes four side surfaces alternating with four corner surfaces, the side surfaces and the corner surfaces intersecting the top surface to form a top main cutting edge and a top corner cutting edge, respectively. Each side surface has a middle surface and a top main backlash surface. Each top main relief surface forms an acute internal top main relief angle with a mid-plane, and the mid-plane intersects four intermediate surfaces to define an imaginary mid-square. In a top end view of the cutting insert, the four top main cutting edges define an imaginary top main square rotationally offset from an imaginary middle square. 在可绕刀具轴线旋转的切削刀具中，可反转切削刀片可拆卸地固定在刀具主体中。切削刀片具有通过外周表面互连的相对的顶部端表面和底部端表面，以及位于它们之间的中平面。外周表面包括与四个角表面交替的四个侧表面，侧表面和角表面与顶表面相交以分别形成