All those who work in the hosiery sector know very well the UNION SPECIAL brand, famous among other things, for overlock used on the sewing and assembly machines for tights, specifically we are talking about the UNION SPECIAL 39500 sewing heads.
Whether they’re the 9M or MARKIV model, both require a transparent plastic cap, housed on the lid, where the hole to supply the machine with oil is located. This cap called “dome” with code 39594Y, in addition to being essential for closing the hole, allows you to see the state of clarity of the lubricating oil.

Over the years, thanks to technical experience and collaboration with our customers, we have realized that the “limit” of this dome was found in the screwing thread. The fragility of the plastic combined with the working vibrations of sewing machine cause cracks, the thread breaks and consequently the oil leaks out because it no longer has the necessary seal; Result, the dome needs to be changed.