When selecting a manual punching machine, you must prioritize the nominal pressure (tonnage) to ensure it meets your material thickness requirements. Key factors include the throat depth, which determines the maximum width of the workpiece, and the stroke length. Look for machines constructed with high-grade cast iron frames for vibration dampening and hardened alloy steel tool heads to ensure longevity. For precision tasks, verify the positioning accuracy and whether the machine supports interchangeable die sets for different hole shapes (round, square, or oblong).