A self contained, toolless quick change tool holder for trigon cutter inserts on machine tools comprises a housing having at least one seat portion which is adapted to receive and conform to the shape of a variant shaped cutter insert. A fork is mounted in the insert housing and is movable within the insert housing. The fork engages a variant shaped cutter insert. A locking mechanism is contained within the housing and has a clamp position which forces the clamp portion to engage a variant shaped cutter insert and a release position which forces the clamp portion to disengage from a variant shaped cutter insert to allow removal and replacement of said variant shaped shaped cutter insert. The locking mechanism moves between the release position and the clamp position.