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Punch to Die Clearance
The relationship of the larger die hole size to
the punch size is called die clearance. This is based on a percentage of the
thickness of the material being punched. The range of clearances varies from 10%
for thin materials to 20% for thicker materials. For 3/4" material the
total die clearance is .150". Clearance should always be specified when
there is any reason for doubt.
Too much
clearance will result in:
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Extra roll-in at top of the hole.
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Too much burr at the bottom of the hole.
Too little clearance
will result in:
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More punching pressure is needed. Can reduce
tool life.
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High stripping force causes part distortion
and extra punch wear.
Correct clearance
will result in:
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Straighter hole thru material.
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Minimum distortion at top of hole.
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Minimum burr at bottom of hole.
The thicker the material the more noticeable are
the effects of die clearance: say 1/4" compared to 1/16".
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