Why was the Bramah lock difficult and expensive to manufacture?

The Bramah lock was difficult and expensive to manufacture primarily due to its high level of complexity. Unlike simpler designs, the Bramah lock operated on an intricate mechanism that required a series of slides to be depressed to precise, varying depths before the bolt could be turned.12

Because of this sophisticated design, the lock could only be produced in quantity through the development of specialized, precisely engineered machine tools. Joseph Bramah and his assistant, Henry Maudslay, had to construct these prototype machines specifically for the purpose of producing the lock's parts mechanically. These efforts were significant, as they represented some of the earliest machine tools designed for mass production and helped establish the foundation for the British machine-tool industry.12