The Real Deal These carriage bolts were used on an early 1800's sleigh (See page on the History of Bolts). The actual sizes are interesting; one is a 1/2"-13 thread, slightly undersized, while the others are 7/16"-12 thread. This is curious, as we think of 7/16" diameters having a standard 14 threads per inch, and 9/16" bolts having 12 threads per inch. The answer is that these were made before the standards became widely accepted. Split dies used in the early days could be made to adapt to a range of diameters. All three bolts are approximately 3" long. The 1/2" bolt, shown at center in the picture, has the smallest head with the least crown. The wingnuts are all between 2-3/8" and 2-1/2" wide. All in all, they look to have been very labor-intensive to produce.