Abstract
The paper describes the various commercial methods of producing screw threads by cutting, rolling, grinding, and milling. The operating principles on which the several processes depend are dealt with and their advantages and limitations are discussed.
A workshop method of determining the torque required for tapping and for threading is described, and a chart based on the results gives figures suitable for determining the power of machines to undertake the tapping or screwing of a wide range of work.
A mathematical treatment of the clearance between the flanks of a tool and a screw thread is given. This permits the investigation of clearances at any point on the tool profile or flank, and enables relief and tilt angles to be chosen to suit various conditions of lead, thread profile, and diameter for both internal and external threads. For design purposes, a simple formula is available which gives clearance angles in relation to the portions of the tools most subject to interference.
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