joint having a ball portion 6 of ball stud 5 with a diameter of 20 mm and a ball seat 9 made of polyacetyl resin the resulting drawing strength is normally approx 130 kg a ball joint according to the present invention however provides a maximum drawing strength of 280 kg referring now to fig2 data is presented showing actual measurements of the relationship between the distance between the smallest diameter part and socket 1 and the drawing strength of ball stud 5 it will be noted that the drawing strength changes by a factor of about two over a distance of about 1 mm referring now to fig3 another embodiment of the present invention employs a ball stud 5 having a ball portion 6 with cylindrical shank portions 7 protruding from both ends of ball portion 6 a ball seat 9 is open at both ends a dust cover 12 is attached between each shank portion 7 and its respective end of socket 1 thereby covering both openings of ball seat 9 with dust covers 12 in the same manner the present invention is applicable to a ball joint wherein the shank is inserted through the center of ball stud 5 according to the present invention it is possible to position the smallest diameter part of the opening of the ball seat 9 close to or within the end of the socket 1 by forming a recessed part 22 around the outer surface of the end of the socket 1 and fitting the attaching part 13 of the dust cover 12 in the area from the recessed part 22 to the receiving part 23 of the ball seat 9 therefore the present invention makes it possible to limit the required aperture of the.