Filament trimmer head

A filament trimmer has an improved trimmer head. The trimmer head includes a spool having crush ribs on its core to prevent contraction of the filament line from warping or otherwise damaging the spool. A slot shaped exit aperture is provided in the head which can be opened up when the head is disassembled to allow the filament line to be more easily placed therein, but which will be closed when the head is fully assembled and will constrain the line against excessive vertical movement. The head includes a line indexing system for feeding out additional line in which one of the groups of the conventional teeth in such system are vertically spaced away from the spool flanges and are placed on a spool core extension. A dirt seal is provided to help prevent from passing around the ground engaging member of the indexing system. Finally, the head includes a self threading drive shaft that forms the attachment threads for the head into the head when the head is threaded onto the drive shaft.