is in the present example twice the length b of the smaller semi axis minor axis of the ellipse the length of the large semi axis of the ellipse major axis has a dimension a the thread shape of the corresponding threaded bushing is shown in detail in fig4 as can be seen the thread profile including both thread flanks and the thread crest form a segment of a single ellipse the threaded roots of the threaded bushing of fig3 and 4 are also rounded with the radius r commensurate with the thread shape of the threaded plug the major axes of both ellipses of the threaded plug and the threaded bushing are each oriented perpendicular to the envelope defined by the roots of the thread the thread depth t determines the geometric location of the ellipse in relation to the envelope the pitch of the thread depends on the length of the minor axes of the ellipses and is in the present example about 7 mm the threaded plug of fig1 and the threaded bushing of fig3 each have a chamfer the chamfer of the threaded plug is defined by the chamfer dimension x and the chamfer angle y the chamfer of the threaded bushing is defined by the chamfer dimension a of the threaded bushing and by the chamfer angle y which is identical to the chamfer angle x of the threaded plug the chamfer dimension x should be at least.