Patent ID: 8307890

Claim:
A whipstock assembly for milling an aperture in a casing, the whipstock assembly comprising a milling device and a whipstock, wherein: the whipstock has a longitudinal axis, and a deflection face having a surface which is angled with respect to the longitudinal axis to guide the milling device through the casing; and the milling device is adapted to be connected to the whipstock, the milling device having upper and lower milling heads arranged sequentially on the milling device; wherein the whipstock has a plateau portion raised above the surface of the deflection face to support the lower milling head as the lower milling head engages the casing, wherein the interaction of the lower milling head with the plateau portion causes the milling device to pivot around one of the milling heads, changing an angle of the milling device with respect to the casing.