4-49. BUTTON SEWING MACHINE MAINTENANCE ADJUSTMENT PROCEDURES - continued.
To adjust needle bar vibration centrally with looper shaft and with relation to the needle slot in the
When adjusting, make sure that needle clears the left hand and right hand ends of the slot in
Remove feed plate or stay button holder (para. 2-13), needle plate and looper. In place of the
looper, insert a stud or pin in looper stem opening in looper shaft. This pin should be of proper
size to fit snugly in looper shaft (a size 20 drill will serve the purpose).
Loosen hexagon head screw (1) and move lever arm (2) to right or left using the belt pulley until
the needle, on both vibrations, just touches both sides of the projecting stud, pin or drill, then
tighten screw (1).
By this method, It is possible to determine accurately whether both vibrations are exactly equal
distance from the center of the looper shaft.