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
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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| Click to Enlarge |
