As an engineer, I’ve found NASA’s Installation Torque Tables for Noncritical Applications (NASA/TM-2017-219475) to be an invaluable resource for determining appropriate torque specifications both during the design process and for publishing recommendations to the end user.
This tool began as a simple lookup interface for the data tabulated in NASA’s publication, but gradually grew to fill in a few limitations – namely support for more thread and fastener materials. This tool follows the NASA methodology for determining and recommending assembly torque specifications with the goal of being an easy to use interface that doesn’t require manually interpolating tabulated data.
For more information about how exactly this tool works and its limitations, read the documentation.