If the four bolts securing the machine head to the table are loose, the entire machine vibrates at high speed. This harmonic vibration acts like a jackhammer on the top casing, specifically around the arm-to-base joint.
In these cases, either source a replacement top casing from Juki or invest in a new machine. A Juki PM1 top casing typically retails for $400–$700. A full new Juki DDL-8700 or DDL-9000 series head is around $1,200. Compare that to 10 hours of technician labor welding and machining a crack—the math favors replacement. juki pm1 crack top
Observed / Assumed Details