This article describes one easy way to make the guards for bow irons. An alternative way is described this article.
Many thanks to Ville Huhta from Rautaportti Ky for providing the necessary tools, designing and making these parts with me and for taking the photographs.
Start by marking the places where to grind:
Next grind away half of the thickness of the rod at one end, cut the guard to correct length and grind the other end:
In the picture below (at top left) you'll see what the guards should look like at this point:
Next put the guard into a vise and heat the thin end with a blow torch (or in a forge):
Once sufficiently hot, hammer the thin end into a 90 degree angle over itself as shown below:
The resulting guards should look like this (above and below the wedges):
Not exactly pretty, but functional and relatively quick to make.