The world's most common thread? This must be the 1/4" x 20 t.p.i. Whitworth form found in the base of a camera that allows it to be fitted to a tripod or other mount. It's common to every camera maker and every model they produce - though some heavier professional types have, as a concession, fitted with a more robust 3/8" x 16 t.p.i.

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