Thread Heaven is for hand sewing. It's good stuff. I use Sewer's Aid for machine sewing. I put a couple of drops on the spool of thread. It really helps when winding a bobbin. And if you put a drop or two in you hand and apply it to your hair, it's great to bring shine and stop the fly away frizzies. It's much cheaper then buying the product in the hair aisle and it's the very same thing. The hair product is thinner and cost 3x as much.
I've used Swerer'sAid on thread in every machine I have, even my computer one. No build up are any problems at all.