John H. Hall (soldier) - Career

Career

On May 21, 1811, Hall patented a single shot, breech-loading rifle in collusion with Washington, D.C. architect, Dr. William Thornton. He began manufacturing his new rifles at the rate of 50 per year until the Ordnance Corps (United States Army) ordered 200 rifles in December 1814. He regretfully turned down the contract because he was unable to meet the Army delivery deadline of 1815. Hall recognized individually fitted parts as the factor slowing rifle production, and adapted his breech-loading design to the “uniformity principle,” widely known as interchangeable parts. Hall proposed the concept of interchangeable parts to the Army in June, 1816, and earned a contract for 1,000 of the "Model of 1819" Hall rifles from the War Department with interchangeable parts being the chief condition. To fulfill it, Hall spent more than five years (and $150,000 of government funds) at Harpers Ferry Arsenal, where he occupied an old sawmill on a small island in the Shenandoah River called Virginius Island.

Hall's methods were novel for the time period. Hall transferred water power through a system of leather belts and pulleys to power his machines with unusual pace, greater than 3,000 revolutions per minute with efficiency, while most artisans used hand cutters and files. Like his contemporary Simeon North, Hall began using this mill power to run machine tools and achieve the dimension controls necessary for interchangeable parts. He employed metal-cutting machines attached with cutters and saws in the place of the standard heavy labor, made from cast-iron frames to ensure structural integrity and minimize vibrations from the mill’s belts. These machine-cut surfaces would then be hand filed to ensure fit and interchangeability, verified by a gauging system Hall had designed.