The IndustrialCraft Wrench is used to dismantle machines and also to rotate the output faces of energy storage devices, such as BatBoxes, MFEs, MFSUs and Transformers. To dismantle or change the output face of a machine, simply right click with the wrench. Using any other tool to dismantle a machine will result in only dropping a machine block.
Additionally, there is a 20% chance, even when using a wrench, that your machine will not return itself. Specialized generators may return normal generators, and other machines may return a Machine Block. The other 80% is the chance that a machine will return itself. This cannot be prevented.
An alternative to this wrench is an Electric Wrench, which performs the same functions without losing durability, however it does require electricity. The Electric Wrench also has a "Lossless" mode that will always return machines intact.