After cooling, use a carbide burr and then fine files to bring the surface back to flat. The needle bar bushing bore must be perfectly perpendicular to the hook axis. Check with a dial indicator. If the weld warped the bore, you will need a line-boring machine (often more expensive than a new top casing).
Drill a tiny 1.5mm hole at each end of the crack. This “stop hole” prevents the crack from propagating further during welding. Then, use a die grinder to carve a “V” groove along the entire length of the crack—about 60% of the material depth. juki pm1 crack top
If you are an industrial sewing machine operator, a sample maker, or a high-volume apparel manufacturer, you know the value of the Juki brand. Specifically, the Juki PM1 (a variant of the renowned DDL-8700 or similar lockstitch models) is celebrated for its durability, speed, and precision. However, no machine is invincible. Among the more niche yet critical issues that surface in technician forums and factory floors is the problem of the “Juki PM1 crack top.” After cooling, use a carbide burr and then