1.  Field
This disclosure relates to a medical use driver tool and, in particular, to a torque-limiting driver that disengages at a predefined torque limit. 
2.  General Background
Torque-limiting drivers are widely used throughout the medical industry.  These torque-limiting drivers have a factory pre-set torque to ensure the accuracy and toughness required to meet a demanding surgical environment. 
The medical industry has made use of both reusable and disposable torque-limiting drivers.  In a surgical context, there is little room for error and these drivers must impart a precise amount of torque. 
Reusable drivers require constant recalibration to ensure that the driver is imparting the precise amount of torque.  Recalibration is a cumbersome task but must be done routinely. 
Disposable drivers are an easy to use and reliable alternative to the reusable drivers.  Typically, a medical device such as an implant, for example, is packaged with a disposable driver designed to the implant's specifications.  Once the driver has been used, it can be discarded.  Thus, a surgeon can have complete confidence that the disposable driver, packaged with an implant, will impart the precise amount of torque.  Typically, the torque requirement is different for different operations and for different implants.  For example, applications may include those in the field of orthopedic surgery, construction and emplacement of implants, etc. 
These disposable drivers have been used for low torque applications.  The standard torque values in these applications typically range from 4 to 20 inch-ounces.  It has, however, been a challenge to develop a reliable disposable driver capable of imparting higher torques for larger applications.