Commutator forming plate, commutator, motor with commutator and manufacturing the same

In a commutator forming plate to be rounded into a cylinder which is to be cut at constant angular intervals to form a plurality of commutator segments after being filled with insulating material, a plurality of lands rising at given intervals on one surface of a plate is provided and a plurality of projecting portions protruding nearly perpendicular to a rising direction of each of the lands are formed simultaneously by forming a plurality of grooves crossing with each other on the respective lands and extending so as to intersect obliquely with respective outer peripheries of the lands.