Method for integrally forming a stop flange on a self-tapping screw by threading dies

A method for forming a stop flange on a self-tapping screw, comprising:

• locating a shank of a self-tapping screw between two threading dies;
• each of the two threading dies having an external thread forming section;
• each of the two threading dies having a notch located at a top of the external thread forming section;
• the notch including an upper ramp and a lower ramp;
• the notch having a dimension decreased gradually from a starting position to an ending position thereof;
• the notch having a top provided with an insert;
• the insert having a dimension increased gradually from a starting position to an ending position thereof;
• the insert having a top provided with a recessed corner;
• the recessed corner having a flat shape;
• fixing one of the two threading dies and moving the other one of the two threading dies to work the shank of the self-tapping screw;
• the external thread forming section of each of the two threading dies performing threading to form an external thread on the shank of the self-tapping screw;
• inserting the insert and the recessed corner of each of the two threading dies into a top of the external thread to form a groove in the shank of the self-tapping screw;
• and
• the insert of each of the two threading dies gradually squeezing downward an extruded portion that is formed during formation of the groove to form a stop flange on the shank of the self-tapping screw by the extruded portion.