Expander nut structure for a handlebar stem

A handlebar stem having a quill tube and an expander nut structure comprising:

• an insert selectively positioned within an end of a cylindrical quill tube adapted to be inserted into a steering tube, the insert having a narrowed cylindrical section disposed within the quill tube and a cylindrical external section having a sidewall aligned with the quill tube and of substantially equal outer diameter to an outer diameter of the quill tube;
• the external section of the insert joining the quill tube at a joint substantially perpendicular relative to the sidewall of the insert, the insert having a lowermost edge defining a plane, the plane being slanted with respect to the sidewall so that an angle between the sidewall and the plane taken from a lowermost point of the lowermost edge is less than a right angle, the plane passing through the perpendicular joint and upwardly into a part of the quill tube sidewall, the part of the quill tube sidewall being shaped to lie within the plane and forming a part of the plane;
• an expander nut having a cylindrical sidewall substantially equal in outer diameter to the outer diameter of the insert sidewall and having an upper surface that defines a slanted non-perpendicular plane relative to the sidewall of the expander nut, the slanted plane being constructed and arranged so that the sidewall of the expander nut is substantially concentric and aligned with the sidewall of the insert and the quill tube when the upper surface of the expander nut mates in a face-to-face relationship with a surface defined by the plane of the lowermost edge of the insert and the quill tube;
• and
• a bolt passing through the insert and engaging a threaded hole in the expander nut when the surfaces thereof mate in the face-to-face relationship, the bolt aligned along a direction substantially parallel to the sidewalls of the insert and the expander nut and the bolt having a head abutting an uppermost surface of the insert disposed within the quill tube so that compression applied by the bolt between the insert and the expander nut causes the expander nut to displace relative to the insert along the mating surfaces in opposite directions to bear against inner walls of the steering tube.