Clearance is Crucial

Correct punch and die clearance is critical during the punching operation. Proper clearance will produce a hole with approximately the top one third measuring the size of the punch and the bottom two thirds flaring to the approximate inside diameter of the die.

Insufficient clearance will usually generate a secondary shear on the material, resulting in additional wear on the punch. Additionally, punching without Punch Easy® lubricant, can contribute to reduced die clearance, as the punch will grow during the punching application.

On the other hand, excessive clearance may result in a large flare as well as a burr on the bottom side of the material. Material “roll-over” may also occur along the top edge of the hole, and may cause the punch’s sharp edge to break down rapidly. The picture below shows an example of the effects of excessive and insufficient clearances. 

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No exact science exists for determining the proper clearance between the punch and die. What may work for one particular type of material may be different for another.

Follow the clearance chart below for the best results when punching mild steel.

Material Thickness                                                          Die Clearance
¼” up to ½”                                                                               1/32”
½” up to ¾”                                                                               1/16”
¾” up to 1”                                                                                3/32”
Over 1”                                                                                     1/8”
Gauge Stock                                                                10% of material thickness

When punching material other than mild steel, this chart may be helpful for determining clearances.

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