What is the Difference in Metric & Conventional Sockets?
Socket wrenches come in two standard varieties: metric and SAE (also called “conventional” sockets.) Metric sockets measure in millimeters, conventional sockets in fractions of an inch.
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History of Conventional Sockets
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In the early 20th century every automotive engineer in the US used different units of measurement. To end confusion the Society of Automotive Engineers (SAE) adopted a variation of the Imperial System of measurement for their wrenches and sockets.
History of Metric Sockets
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In the 17th century every town in France had its own system of measurement. After the French Revolution, the French adopted a standardized system based on the size of the earth. Metric tools such as sockets have since spread throughout the world.
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Benefits of Metric Sockets
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One of the chief differences between metric and conventional sockets is that the metric system sockets are decimal and easy to calculate with. Conventional sockets use fractions of an inch, such as 1/2 and 9/16, which makes calculation difficult.
Different Uses
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Metric and conventional sockets cannot be used on the same machines. Metric sockets are for metric machines, and conventional sockets are for conventional machines. They overlap in one place, though. A 1/2-inch socket is the same size as a 13-mm socket.
Difficulties
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Having both sets of measurement standard in different parts of the world results in many mechanics having to buy two sets of sockets, one metric and the other conventional.
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