Hydraulic punching units With these types of units, we can punch two style of holes: Through holes or with or without a mandrel to prevent deformation An exit bushing is also provided for tooling longevity and preventing deformation. We can also punch without a mandrel and do a single blind or a double blind hole, when a dimple is required for assembly purposes. Multiple hole punching, with or without a mandrel is also a possibility with both our smaller or our larger units.