Joseph R Hebert

US Patent:

54312205, Jul 11, 1995

Filed:

Mar 24, 1994

Appl. No.:

8/217519

Inventors:

W. L. Lennon - Corsicana TX
Joseph V. Hebert - Tomball TX
Thomas F. Bailey - Houston TX
John E. Campbell - Houston TX

Assignee:

Smith International, Inc. - Houston TX

International Classification:

E21B 708
E21B 2300

US Classification:

166 557

Abstract:

A starter mill adapted for use with a whipstock to mill a window through the casing of a well for deviating the direction of drilling. The starter mill includes a bearing nose which is utilized to indicate completion of the milling process. As the mill nears completion of the milling process, the bearing nose will become wedged between the whipstock face and the casing preventing further downhole movement. The bearing nose will engage whipstock and casing, allowing the work string to continue to rotate although the decreased torque resulting from the absence of milling provides a clear signal that the milling operation is complete. The cutters of the mill are spaced a predetermined distance from the bearing nose to ensure completion of the casing window.