This started as Knife Knapping, which had a new recipe for 3 Knife blades instead of two. Thanks to feedback on the forum from Jesse Caron, I upgraded all of the recipes. Now you get 2 axes, 2 hoes, 2 spearheads, 3 knives, and 8 arrowheads. The shovel model is slightly adjusted as well, but it's far too big to make 2 at once, so it's only a cosmetic change. 

Since this obsoletes Knife Knapping it would be best to remove the old one. Might not make any difference, but if this simple mod actually manages to cause a crash, that would probably be the only possible reason. 

Update 1.0.1: Fixed the Axe recipes to include knapping the sharp edge. This also takes care of the problem that the recipe was just too simple.