Hinged Knife

The idea is pretty simple: take a knife, put a (vertical) hinge in the middle, then cut up any circular food to exact measurements. My proposition is that there be a small pin at the top of the hinge, which first of all is inscribed with various values around its side to allow the food to be divided into thirds, quarters, sixths, twelfths, &c. &c., and secondly to lock the blade in place when the desired angle has been achieved. Since there can't be any slicing movement, the blade has to be adequately sharp, and there could be handles at both ends of the blade, as well as one at the hinge, for extra leverage. Both blades would have to be quite long, maybe 10 inches to accommodate the largest of pizzas and cakes.