Selecting a planishing hammer requires balancing pneumatic power, frame rigidity, and die versatility. For heavy-duty metal shaping, prioritize a cast iron or heavy-duty steel C-frame to minimize deflection during operation. Ensure the tool offers a variable speed foot pedal for precise control over the beats per minute (BPM), typically ranging from 800 to 4,500 BPM. Additionally, verify that the hammer includes a set of hardened steel dies (radius and flat) to accommodate different curvatures and metal thicknesses.