A turbine blade assembly may be provided for use in a gas turbine engine. The turbine blade assembly may include an airfoil and a tip shroud. The airfoil may extend radially outward from an axis of rotation of the airfoil. The tip shroud may be located at a radial end of the airfoil. The tip shroud may include a seal rail that extends in a direction of rotation of the airfoil. A notch, including a Z-notch or a V-notch, may be situated on a first side of the seal rail at an end of the seal rail. A variable fillet may be situated on a second side of the seal rail that is opposite of the first side on which the notch is situated. The variable fillet is a fillet having a curvature that varies along a length of the second side.