A while back I shared a video on how to tie the Double Surgeons Knot. The Blood Knot is used to accomplish the same task, to splice two pieces of tippet together. However, there are a few differences between these two knots.
Day in and day out on the stream, I’m going to use the Double Surgeons. It’s quick and easy to tie and it’s a little bit stronger. It also does a better job than the Blood Knot when it comes to connecting tippet that varies significantly in diameter.
The downside to the Surgeons Knot is that it sets a little cockeyed and it’s a little bulkier knot. Neither of these things matter much when you’re working with 5X tippet. You probably won’t even notice. But when you’re splicing thicker pieces of mono together, like butt and mid sections of leader, a more uniform and less bulky knot becomes extremely important. And that’s when the Blood Knot is at it’s best.
Additionally, I’ll sometimes use the Blood Knot with smaller tippet if I’m rigging a two fly rig where I want the top fly to swing independently, rather than fixed as with the in-line system. Fishing two wet flies is a perfect example of when I might do this. I can tie a Blood Knot and leave one of the tags long to attach the top fly. The tag ends on a Blood Knot come out at a perfect right angle and foul far less than the cockeyed tags on a Double Surgeons.