A prewinder apparatus for attachment to a drive tool for installation of a helical coil insert, the prewinder apparatus comprising: a body for connection to the drive tool; an adapter rotatable with respect to the body and releasably connected to the body at operator selected ones of a plurality of rotated positions, the adapter defining a flat surface portion having an elongated cavity therewithin; and a fastener engaged with the prewinder portion having a fastener head axially movable within the elongated cavity; a prewinder portion slidably displaceable into and out of the body coaxial to a longitudinal axis of the body and the adapter, and biased by a first biasing member toward an extended position; a mandrel axially extensible from the prewinder portion when the prewinder portion is slidably displaced into the body against a biasing force of the first biasing member, the mandrel adapted to engage the helical coil insert to rotatably insert the coil insert; and the prewinder apparatus, further including: a plurality of insert engagement threads created in the adapter; and a threaded insert having: a plurality of insert threads adapted to engage the plurality of insert engagement threads and a threaded insert body extending into the elongated cavity of the adapter to allow axial displacement while preventing rotation of the threaded insert, permitting infinitely adjustable axial displacement of the threaded insert in the elongated cavity by rotation of the adapter such that the threaded insert creates a stop position for axial travel of the prewinder portion by contact between the fastener head and the threaded insert, the stop position further defining a depth of insertion of the coil insert. a body for connection to the drive tool; an adapter rotatable with respect to the body and releasably connected to the body at operator selected ones of a plurality of rotated positions, the adapter defining a flat surface portion having an elongated cavity therewithin; and a fastener engaged with the prewinder portion having a fastener head axially movable within the elongated cavity; a prewinder portion slidably displaceable into and out of the body coaxial to a longitudinal axis of the body and the adapter, and biased by a first biasing member toward an extended position; a mandrel axially extensible from the prewinder portion when the prewinder portion is slidably displaced into the body against a biasing force of the first biasing member, the mandrel adapted to engage the helical coil insert to rotatably insert the coil insert; and a plurality of insert engagement threads created in the adapter; and a threaded insert having: a plurality of insert threads adapted to engage the plurality of insert engagement threads and a threaded insert body extending into the elongated cavity of the adapter to allow axial displacement while preventing rotation of the threaded insert, permitting infinitely adjustable axial displacement of the threaded insert in the elongated cavity by rotation of the adapter such that the threaded insert creates a stop position for axial travel of the prewinder portion by contact between the fastener head and the threaded insert, the stop position further defining a depth of insertion of the coil insert. a plurality of insert threads adapted to engage the plurality of insert engagement threads and a threaded insert body extending into the elongated cavity of the adapter to allow axial displacement while preventing rotation of the threaded insert, permitting infinitely adjustable axial displacement of the threaded insert in the elongated cavity by rotation of the adapter such that the threaded insert creates a stop position for axial travel of the prewinder portion by contact between the fastener head and the threaded insert, the stop position further defining a depth of insertion of the coil insert.