The selection of gaps in metal stretching molds should achieve good cross-sectional quality, high dimensional accuracy, and low punching force, which usually results in a longer lifespan of the metal stretching mold. The reasonable gap of hardware stretching molds refers to a range of values, including the maximum reasonable gap and the minimum reasonable gap. The determination of the gap of the metal stretching mold is based on a comprehensive consideration of the influence of the gap on the cutting force, the influence of the mold life, the influence of the cross-sectional quality, etc., and selecting an appropriate gap range as the reasonable gap of the metal stretching mold. The upper limit is the maximum reasonable clearance, and the lower limit is the minimum reasonable clearance, which refers to a range of values. When designing the hardware stretching mold, it can be done according to the specific requirements of the workpiece and production. When there are no strict requirements for the cross-sectional quality of the workpiece, a larger gap value can be chosen to improve the service life of the metal stretching mold and reduce the punching force. When the cross-sectional quality and manufacturing tolerance requirements of the workpiece are high, a smaller gap value should be selected. The determination criteria for hardware stretching molds need to pay attention to the above points. The main factors affecting the gap value are material properties and material thickness. The harder or thicker the material, the larger the gap value.