The problem of computing the torque and thrust developed on a drill is approached from dimensional reasoning and the rules of cutting-force development in two-dimensional cutting. The drill quantity equivalent to the feed in ordinary machining is found to be the product of feed and diameter. General equations are derived for drill torque and thrust and found to be in good agreement with experimental data obtained by use of a drill dynamometer. The web thickness of the drill is found to influence thrust and torque significantly, but the influence of helix angle is found to be relatively unimportant.

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