Sintered member and electromagnetic coupling

An electromagnetic coupling comprising:

• a first cam;
• a second cam;
• and
• a ball interposed between the first cam and the second cam, wherein
• the first cam being a sintered member having an annular shape, the sintered member including
• a first face facing one side in an axial direction,
• a second face facing the other side in the axial direction,
• an inner peripheral face connected to an inner peripheral edge of the first face, and
• a plurality of tooth groups and a plurality of tooth-missing parts which are alternately disposed along a circumferential direction of the inner peripheral face, wherein
• the second face includes a plurality of ball grooves arranged in parallel in the circumferential direction,
• each tooth group includes a plurality of spline teeth that are continuous in the circumferential direction of the peripheral face,
• the number of the plurality of tooth-missing parts is the same as the number of the plurality of ball grooves,
• positions in a radial direction in which the plurality of tooth-missing parts are formed are within ranges in the radial direction in which the plurality of ball grooves are formed, and
• ranges in the circumferential direction in which the plurality of tooth-missing parts are formed overlap ranges in the circumferential direction in which the plurality of ball grooves are formed.