I point the business end and then wrap around a piece of pipe. I would guess 3" would work well for 1/2" rod. Wrap it so each turn is touching the last (picture a tension spring at rest). Remove from mandrel. Then take an even heat on the whole thing and gently pull from each end to stretch. Then with a local heat bend the top end 90 like Hollis said above to be in line with the screw.
The last one of these I made was for a giant foam lemon whose original hanger had pulled out. It was for display at a food stand for friends at the state fair.
I helped a friend make a couple large anchors of this type for a wooden jib crane in his yard. Instead of wrapping hot around a mandrel we did the coils cold on the hossfeld and then heated to stretch. They turned out great. He is left handed, I am left handed, and so were the anchors!
