Snapping your hand off is a turn of phrase, similar to bite your hand off. It means you'd be very very grateful for it, so grateful that when they gave out their hand to metaphorically offer you the draw, you'd be so eager in taking the draw, that you'd also snap their arm off.and what snapping my hand off has to do with a draw?
you made some fair point, but still, for me, the draw with them looks more likely than looked the win over Sheffield today, though I do understand that is beyond logical reasoning.