The cutter blades of the cutter heads of the present machine are supported in such a manner that they may be quickly and accurately adjusted for varying the cutting depth of the cutter blades. The cutter blades are supported in groove-shaped receptacles equally spaced around the cutter head and means is provided for adjustably supporting and positively locking the cutter blades in the desired adjusted position in the groove-shaped receptacles. An adjusting plate is fixed to the cutter blade by mating sawtoothlike grooves to provide a primary adjustment of the cutter blades. The adjustment plate including a guide surface which includes a gradient component extending in at least one adjustment direction of the cutting blade so that secondary adjustments may be made to the position of the cutter blade.