Causes of Premature Wear on Punches and Dies

• Improper alignment of the punch and die
  Misalignment causes the punch to shear into the die, making it appear naturally worn. If a punch shows wear on one side only, the cause is usually improper alignment.
   

• Excessive stripping force
  Insufficent clearance between the punch and die can drastically increase stripping force. Proper clearance results in a stripping force of approximately 20% of punching force. Insufficient clearance can increase stripping up to 30%. Since wear is typically proportional to applied force, proper clearance greatly extends tool life.
   
• Nibbling
  Nibbling while using a standard punch causes the punch to be thrust sideways and shear into the die. When nibbling or notching, a punch that has a guide heel should be used to avoid sideways thrust.
   
• Hard and/or abrasive materials
  Standard punches usually are subject to premature wear on extremely hard or abrasive materials. A better grade of tool steel, such as high-speed steel, should be used if at all possible. Cutting or die lubricant is highly recommended in these applications.
   
• Tapered parts
  Punching a tapered part without using dies with a proper bevel will cause excessive wear. For best results and extended tool life, a die that has been beveled to match the taper of the part should be used.
   
• Soft, "gummy" materials
  Soft materials such as copper and aluminum tend to gall and stick to the punch. Use of a lubricant will increase the life of the punch and die.
   
• Sharpening punch and die too late
  A punch and die should be sharpened when the sharp cutting edge can be restored after grinding .015". If they are used beyond this point, wear increases very rapidly. The number of holes punched before sharpening is needed varies greatly with the type and thickness of the material.

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