Adjustable length punch assemblies are disclosed. An adjustable length punch assembly in accordance with present invention may be used with a punch press including a tool holder adapted to receive punch assembly and a ram adapted to move longitudinally along a ram axis. An adjustable length punch assembly in accordance with present invention preferably includes a punch body assembly disposed in threading engagement with a drive body assembly having a surface adapted to be struck by ram of punch press. The length of punch assembly may be adjusted by rotating of one body relative to other body. The adjustable length punch assembly preferably includes a lock mechanism for selectively preventing rotation of the punch body assembly relative to the drive body assembly. The lock mechanism preferably comprises a lock shaft coupled to one of bodies and a lock key slidingly coupled to other of bodies such that lock key slides along a lock key path. The lock key path is preferably disposed at an angle relative to ram axis when punch assembly is received by tool holder.