Cutting insert

A cutting insert fixed fixable to a tool body to compose an indexable milling tool, the cutting insert comprising:

• a first end surface;
• a second end surface on an opposite side to the first end surface;
• and
• a peripheral side surface joining the first end surface and the second end surface together, the cutting insert being configured as a vertically mounted insert having a mounting hole formed to extend through the peripheral side surface,
• the second end surface having:
• a third major cutting edge formed on an outer periphery of the second end surface,
• the first end surface having:
• a first major cutting edge formed on an outer periphery of the first end surface;
• a first rake face located further inward of the first end surface than the first major cutting edge and adjacent to the first major cutting edge;
• a second major cutting edge formed on the outer periphery of the first end surface and facing the first major cutting edge;
• a second rake face located further inward of the first end surface than the second major cutting edge and adjacent to the second major cutting edge;
• a restraint surface located further inward than each of the first rake face and the second rake face to come into contact with the tool body when the third major cutting edge is used;
• and
• a reinforcing portion projecting from the restraint surface in a direction from the second end surface to the first end surface,
• the reinforcing portion having:
• a third projecting ridge provided to extend between the first rake face and the second rake face and halve the restraint surface;
• a first projecting ridge connected to a first end of the third projecting ridge to extend so as to cover at least a portion of a boundary between the first rake face and the restraint surface;
• and
• a second projecting ridge connected to a second end of the third projecting ridge to extend so as to cover at least a portion of a boundary between the second rake face and the restraint surface, wherein
• the outer periphery of the first end surface is formed in a substantially rectangular shape having first to four corners,
• the first major cutting edge is located on a long side of the rectangle between the first corner formed with a corner cutting edge and the fourth corner formed with no corner cutting edge, and
• the first projecting ridge is not disposed between the first end of the third projecting ridge and the fourth corner, while being disposed between the first end of the third projecting ridge and the first corner.