The figure shows one aspect of the exterior appearance of a pistol-grip torque-measuring power tool. The tool is a self-contained, computer controlled, 3/8-in. (~9.5-mm) drive pistol-grip style tool. The tool is intended for use in assembly operations in which application of precise torques to fasteners is critical to safety. In comparison with controlled-torque industrial and commercial power tools now in use, the tool offers advantages of small volume and more precise control of torque. It can also be operated under battery power, with battery life extended relative to battery lives of similar commercial power tools.

The tool is capable of generating torques up to 25 lb-ft (34 N-m) and operating at speeds up to 60 revolutions/min. Numerous torque, speed, and turn count limits can be programmed into the tool through the tool's serial port. The tool is 14.17 long by 15.18 in. high (36.0 by 38.6 cm), with battery, and 2.75 in. (7.0 cm) wide.

Whereas currently available controlled-torque power tools feature open-loop servocontrol with poor torque-control accuracy, the tool includes a computer-based closed-loop servocontrol system that is programmed via software. The tool provides excellent torque-control accuracy. For each significant torque application event, the tool records data in its nonvolatile memory. Each datum characterizes the maximum applied torque and angle rotated after a threshold torque is reached. The data may be downloaded to a separate computer to ascertain the quality of the torque application and to diagnose the condition of the tool.

This Pistol-Grip Power Tool resembles other pistol-grip power tools in some respects, but is smaller and provides better control over applied torques.

This work was done by Paul W. Richards, Ken Wagner, Robyn King, and Chan Park of Goddard Space Flight Center; Carl Konkel, Chris Smith, Joe Rosol, and Leland VanAllen of Orbital Sciences Corp.; and Lee Brown, Randy Frey, and Mike Garrah of Swales. For further information, access the Technical Support Package (TSP) free on-line at  under the Machinery/Automation category.

This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to

the Patent Counsel
Goddard Space Flight Center; (301) 286-7351.

Refer to GSC-13706.