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thread

A unit of length used in spinning yarn. It is based on the size of the reel on which the yarn is wound, and is the amount of yarn taken up by one revolution of the reel.

Yarn type	Length of thread
worsted	36 inches	80 threads = 1 rap or lea
cotton	1½ yards	80 threads = 1 rap or lea
Irish linen	2½ yards	120 threads = 1 cut or lea
Yorkshire linen	3 yards	100 threads = 1 cut or lea

Fred Bradbury.
Calculations in Yarns and Fabrics. Third Edition.
Belfast: author, [no date, post WWI, 1920?]

Pages 14, 18, 21.