4-49. BUTTON SEWING MACHINE MAINTENANCE ADJUSTMENT PROCEDURES - continued.
To time the needle bar vibration (With machine at stop locked position).
Set cam (1) to bring the arrow on its rim in alignment with arrow on needle bar vibrating lever
arm (2). With cam (1) in proper time, needle bar vibration will start about ½ inch from top of
upward stroke of needle bar.
To adjust, loosen the two screws (1) in worm gear (2). These screws are located between the
under side of machine bed and the large cam (3) (underneath the machine bed).