A working of two streaks of cord grooves in a key plate is inefficient, and there is a problem that is is difficult to secure the desired precision of the cord grooves. The present invention provides the key plate and the method for manufacturing thereof for solving such problems.
That is, the rear end portion of one cord groove 11 in a key plate K 1 is connected to the rear end portion of the other cord groove 12 through a connecting groove 13, whereby the milling cutter C worked the cord groove 11, works connecting groove 13 continuously, and further works cord groove 12 continuously. Therefore, without returning the milling cutter C back to the original position thereof, the cord groove 11, connecting groove 13 and cord groove 12 can be worked at a time, thereby being able to reduce the time necessary to work the cord grooves. The thus worked connecting groove 13 can be used as a groove which permits the movement of a dog plate 23 of a cylinder lock L in the merging direction thereof.