Circa 1884, the Westinghouse Air Brake Company was experimenting & developing the railroad air brake. Though the new concept was correct, the early execution was far from perfect. Crude manufacturing resulted in the high pressure air leaking out, causing poor stopping power/distances. Westinghouse crews spend some degree of time altering & tweaking the air brake units, and re-installing them on test RR cars, only to find repeated unsatisfactory performance.
A traveling salesman, a representative for a tool & machine manufacturer, stopped at Westinghouse and became involved as an observer to these tests. After some discussions on machining with Westinghouse engineers, said salesman met with the skeptical superintendent, and convinced him to allow the salesman a small quantity of rough castings to take back to his firm. On an improvised machine, the salesman (also learned in the machinist's trade), finished a complete set of parts by precision grinding them to close tolerances.
Returning to Westinghouse, the salesman observed said parts in their first trial test. They performed with excellence, and the salesman accepted a quantity order for grinding machines. The salesman expected the machines might not be well understood in their operation, and offered to send along some mechanics for instruction. Westinghouse declined, with the result that after a few months, the machines were judged to be useless.
The salesman returned himself, gave demonstration & instruction, and within a few days all machines were successfully operational and producing consistent, quality products.
The lesson proved was that parts accurately made could hold air under high pressure, and the air brake became a long-standing railroad industry standard.
The salesman/machinist worked for the Brown & Sharpe Manufacturing Company of Providence RI, and went by the given name of Henry Martyn Leland, future founder of Cadillac.