Two ways to put twist in
Both TFO and ring twisting turn singles into a plied thread. The mill runs both, and the choice belongs in the specification because it changes how the thread behaves on your machine.
What TFO does
Two-for-one twisting inserts two turns of twist per spindle revolution. It produces a large package in one pass, with even twist along the length, which matters on long uninterrupted sewing runs.
What ring twisting does
Ring twisting is the older route and produces a smaller package. It is still specified where a customer has qualified a thread on a ring-twisted reference and does not want to requalify.
How to decide
If you have no existing reference, TFO is the usual choice for sewing thread. If you are replacing an existing supplier, match whatever your approved sample was twisted on, then test.
