What specification covers dimensional requirements for roll threaded hex bolts and square head bolts?
ANSI/ASME B18.2.1 is the dimensional specification that covers hex bolts and square head bolts. Note 14 of the specification addresses reduced body material that is used in the roll threading process.
“14. Reduced Diameter Body. Bolts may be obtained in “reduced diameter body.” Where “reduced diameter body” is specified, the body diameter may be reduced to approximately the pitch diameter of the thread. A shoulder of the full body diameter under the head may be supplied at option of the manufacturer.”
B18.2.1 covers the dimensional requirements for both roll threaded fasteners and cut threaded fasteners. The specification allows for material the size of the pitch diameter of the threaded portion of the bolt to be used in the roll threading process and still be acceptable as long as it meets all other requirements. The same dimensional requirements apply for both roll threaded and cut threaded fasteners and are outlined in B18.2.1. The only difference is that roll threaded bolts have a slightly reduced diameter body.