| My machine's thread spindle became gummy from the adhesives on the thread end caps. To clean it off without a trace of residue, I used the swabs (BD Alcohol Swabs) sold to clean skin before injections. These individually-wrapped swabs contain enough alcohol to dissolve adhesives, but not enough to drip or spill. The swabs are convenient and cheap.
I have used these swabs on phone ear pieces, scissors blades, hard plastic machine parts, metal parts, buttons, gummy needles, and even on some fabrics. Besides the adhesives, alcohol dissolves most small grease spots and spots of dirt from hard surfaces.