by a spring 74 into driving relation against the drive disk secured to the lower extremity of the main shaft 22 is a crank arm 80 pivoted at 81 to a connecting link 82 which is in turn connected to a shuttle carrier 83 slidable in the shuttle race 25 a pivot pin 84 connecting the link 82 to the shuttle carrier extends through a slot 85 in the bottom wall 26 of the shuttle race 25 a boat type shuttle 86 in the shuttle carrier 83 is reciprocated along the shuttle race by the crank arm 80 so as to move back and forth past a needle accommodating notch 90 formed in the second wall 27 of the shuttle race preferably the notch 90 forms an aperture through the shuttle race bottom wall in which the thread carrying needle 45 is free to reciprocate the novel fastening means for the sewing head module described above provides a degree of adjustment for the path of endwise reciprocation of the needle facilitating alignment thereof with the notch 90 in the shuttle race the interrelation of the skeletal frame 11 with the exterior casing 12 13 which will now be described provides an additional degree of control over the cooperative interrelation between stitch forming instrumentalities the exterior casing halves 12 and 13 are preferrably of molded plastic construction with an exterior configuration dictated largely by aesthetic considerations preferably the casing halves when assembled have interior dimensions sufficient to accommodate the skeletal frame with operative parts assembled thereon as illustrated in fig1 in addition each casing half 12 and 13 is formed with a horizontal base section 91 defining.