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 175â€‘lbâ€‘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.