have a torco st40 vise and I need the for the vise
Missing a key word there, but I’m guessing it’s the main screw.
For as inexpensive as those vises are/were, your cheapest option might be to find a parts donor, or a whole new vise, (unless there is sentimental value).
Couple of older threads on them here.
www.garagejournal.com
Otherwise, ebaying for parts, as there probably aren’t new ones available.