X-Acto - Small Concave Wood Carving Blade - X-Acto Small Concave Wood Carving Blade is a 1 and 3/8 inch Concave Carving Knife Blade. Xacto Small Concave Wood Carving Blades are great for detailed carving on curved and convex surfaces such as birds and animal carvings. These blades cut wood, plastic, and plaster. Fits 3/8 inch Type D Xacto Knives and Excel K7 Wood Carving Handles. 2 Blades included.