Forged machinery eye bolts with shoulder, Steel plain finish

Forged machinery eye bolt diameter is measured on the outside of the threads.

Forged machinery eye bolt with shoulder diameter

Resources

Diameter and Thread count
Coarse (standard) thread 1/4"-20 5/16"-18 3/8"-16 7/16"-14 1/2"-13 9/16"-12 5/8"-11 3/4"-10 7/8"-9 1"-8 1-1/8"-7 1-1/4"-7 1-1/2"-6 1-3/4"-5 2"-4.5 2-1/2"-4 Fine thread 1/4"-28 5/16"-24 3/8"-24 7/16"-20 1/2"-20 5/8"-18 3/4"-16 7/8"-14 1"-14 ^

^ NOTE: While 12tpi is the fine thread (UNF) standard, 14tpi is far more common in actual use.