Abstract: Apparatus for compressing against each other for bonding by use of a granule clamp the I and C bars which comprise the O bars from which head cores may be cut, includes a rotating frame so that the angular orientation of the O bars may be changed after embedding them in the granules. This allows bonding glass rods to be placed in the interior openings of the unbonded O bars and then by rotating the frame, cause the glass rods to fall into a position adjacent to the interior edge of the flux gap, and at the same time keep the plane of the flux gaps normal to the axis of the granule clamp's pressure die. When heat is then applied to the unbonded O bars, gravity draws the bonding glass into a fillet adjacent the interior edge of the flux gap.