Setting Screw Thread Standards
In the mid-1800’s, Sir Joseph Whitworth developed the first screw thread standards for a fastening thread which now bears his name. This standard detailed the diameter and pitch combinations along with limits of size for each combination.
Later, Britain, Canada and the United States developed the Unified Screw Thread standard which is in wide use today, and which was copied conceptually by the International Standards Organization when that body standardized the ISO fastener threads and the metric Trapezoidal power screw threads.
Screw Thread Standard Structure
Most screw thread standards are structured as functions of major diameter and pitch. All thread features and limits of size are determined by the thread major diameter and thread pitch. Acme screw threads were formulated in the 1890s to replace square threads and a varied group of other power transmission thread forms. Today, Acme and metric Trapezoidal screw threads are highly standardized by government and industry associations.
Users are guaranteed good fit-ups when using nut and screw products from different manufacturers only if both sources adhere to the applicable standards. For more information about the most common types of screws, view our screw types guide.