Which tool might be necessary to repair a stripped thread in a crankcase?

In the context of repairing a stripped thread in a crankcase, the Heli-Coil is the appropriate tool to use. A Heli-Coil is a type of threaded insert that is used to restore internal threads in a component that has been stripped or damaged. It consists of a coiled wire that is wound into a helical form and is designed to be screwed into the damaged hole, allowing for a new, stronger thread to be created. This ensures that the bolt or screw can be properly secured, which is critical for maintaining the integrity of the crankcase assembly and preventing leaks or failures.

The other tools listed serve different purposes and are not suitable for repairing stripped threads. For example, a torque wrench is used to apply a specific amount of torque to fasteners, ensuring they are tightened to the manufacturer’s specifications. A piston ring tool is specifically designed for installing or removing piston rings in an engine, and a compression gauge is employed to measure the compression pressure in a cylinder. None of these tools have the capability to repair damaged threads, making the Heli-Coil the most relevant and necessary tool in this situation.