A vegetation trimmer with a spool and hub assembly has a cutting filament wound around the spool. The free end of the filament extends through an aperture in the hub into the cutting plane. The spool and hub are rotated at a high rate to allow the filament to cut vegetation. The spool includes a plurality of arms which engage with arms on the hub. When the spool is acted upon, the arms on the spool disengage with the arms on the hub to permit relative rotation of the spool to the hub to feed additional filament into the cutting plane. An indexing feature is used to regulate the amount of additional cutting filament that is allowed to be fed into the cutting plane. When the spool and hub are engaged, the cutting filament is forcible clamped between the arms on the spool and the arms on the hub to prevent the centrifugal force generated by the filament in the cutting plane from acting upon the filament wound around the spool at cutting speed so that the filament does not have means to tangle or weld together and break prematurely. Upon disengagement of the spool and hub, the cutting filament is released to permit the additional cutting filament to be fed into the cutting plane.
