Regardless of whether you complete the thread head with a whip finisher or by the hand whip finish, it is important for aesthetics, balance and strength to pay attention to this last part of the fly’s preparation. Flies come apart at this critical point due to faulty thread wraps or weakly secured materials along the way on the shank. So, extra care at this final juncture to not crowd the eye or to not make loose, minimal wraps must be made.
“Though simple in construction and function, thread heads are, to many tiers, a plague. But a bit of understanding and strategy can make them manageable–even make them pleasant to tie. And the result is a head that is neat, sound.” Thread Heads by Skip Morris