Self-threading yarn brake mechanism

A yarn brake constructed for insuring reliable positioning of a yarn for application of a braking force thereto when the yarn is threaded through the brake, said yarn brake comprising a tubular brake housing having axially spaced apart inlet and outlet openings for passage of a yarn therethrough and an enlarged cavity formed in said tubular housing between said inlet and outlet openings, a pair of cooperating brake platelets mounted in said enlarged cavity, said brake platelets having surface portions positioned in opposing resiliently biased contacting relation for applying a braking force to a yarn passing therebetween, and said brake platelets having peripheral portions cooperating with one another to form a V-shaped groove for guiding the yarn between said opposing contacting surface portions, and said yarn brake having an enclosed sided elongate yarn passageway extending within said cavity from said inlet opening to said outlet opening and past said pair of brake platelets for threading of a yarn through said brake housing, one side of said elongate yarn passageway comprising said peripheral portions of said brake platelets which form said V-shaped groove and the remaining sides being formed by said brake housing to define a lateral width for said passageway less than the width of said peripheral portions whereby said V-shaped groove is positioned for receiving a yarn which is threaded through said passageway and reliably guiding the yarn between said brake platelets without the possibility of lateral deviation therefrom.