Engineers at DeWalt Power Tools and Accessories, Baltimore, were tasked with designing a high-power, right-angle drill that was lightweight, compact, and portable. The drill would need a mechanical clutch to limit maximum torque output to 70 lb-ft. Without it, the drill could transmit up to 175‑lb‑ft torque directly to the technician operating the tool. The DeWalt team quickly determined that the clutching thrust needed in the space available would require a disc spring. Compared to conventional coil springs, disc springs offer higher load capacities in less space. Just as importantly, the drill’s life and performance relied on the disc-spring design.
DeWalt eventually turned to Spirol International Corp., Danielson, Conn., for a custom spring since a standard spring would not do the job. The custom spring had nonstandard dimensions and material, and required a secondary operation to increase cycle life.
When the drill was built and tested, the disc spring helped it achieve a working life far in excess of the design requirement.