The most frustrating part of changing a flat tire can be struggling with bolts that refuse to come loose from a wheel. Samuel Raff, president of the Bethesda Corp. in Bethesda, Md., hopes to come to the aid of stranded motorists.

Raff is developing a torque-limiting socket that creates a spring action between an impact wrench and the bolt. He says the invention will be useful for assemblyline production of large items such as cars and lawnmowers, as well as for tire shops, home hobbyists, and mechanics.

"The impact wrench is a very efficient tool," Raff say, "but it's always been hard for users to control. Finding a way to control the torque, which my socket device would accomplish, would allow the tool to be used 20 times more than it is today."

Raff is looking for a distributor while he works out the invention's bugs: The main problem is durability. He's having trouble finding a manufacturer willing to make the rubber and metal components in quantities suitable for development purposes.