Historically, the biggest bolt ever made was in 1967 by the Penrith Engineering Works company in Scotland. They were enormous - 27' 4" long (8.3m), 4' 2" diameter (1.27m), weighing 12.6 tonnes. 60 of them made for SWISSOIL, in an experiment to increase the capacity of oil tankers by bolting two of them together.Feb 6, 2015