Method of manufacturing yoke of rotary electric machine

A method of manufacturing a yoke comprising the steps of:

• cutting a steel plate into a rectangular sheet to form a plurality of first dovetail convexities and concavities alternately at one end thereof and a plurality of second dovetail convexities and concavities alternately to be loosely fitted to said plurality of first dovetail convexities at the other end;
• rolling said rectangular sheet into a cylinder to fit said plurality of first dovetail convexities and concavities and said plurality of second dovetail convexities and concavities to each other;
• and
• punching said plurality of first dovetail convexities and said plurality of second dovetail convexities at middle portions of borders thereof generally equally at the same time so that the first and second convexities equally deform to fill gaps at the borders and tightly fit to each other.