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Tips for Safe, Successful Punching Mild Steel

Punches should wear out, they should not chip or crack. Several factors may contribute to punch chipping and cracking. Here is a simple check list that will help minimize this failure.

1. Loose coupling nut. This permits the punch to “move” during the punching process. Such movement will cause uneven pressures.

2. Misalignment. If the punch is not aligned to the hole in the die, non-uniform clearance will result. The effect will be uneven pressure on the face of the punch.

3. Improper clearance between punch and die. The accepted standard clearance for punching mild steel that is less than 1/2" thick is 1/32" total clearance. Punching material that is 1/2" or thicker requires a clearance of 1/16". Punching mild steel that is over 3/4" thick may require even more die clearance.

4. Uneven stripping. This occurs when the stripper on the machine does not firmly and uniformly hold the plate down during the “up” stroke. When this happens, the entire weight of the plate, plus the stripping strain, is concentrated on one side or edge of the punch. Under extreme conditions, as much as 1/2" of the punch may break off.

Some of these conditions that we have described can be controlled on your shop floor. However, it is our job to furnish you with the strongest punches possible. We do this by using the finest shock-resistant tool steels available, machine them to exacting tolerances, and then harden and temper them under careful metallurgical procedures.

Punches usually crack and chip when punching high strength, high tensile plates over 1/2" thick. Our engineers have developed several super tough punches which perform well under these difficult conditions.
 

Ensuring Long Tool Life is all About Set-up!

  • Is everything tight?
  • Is punch to die alignment accurate?
  • Is the punch to die clearance correct for material thickness?
  • Is the stripper adjusted correctly?
  • Are all safety guards in place?

If you are breaking, chipping or cracking punches on a regular basis, send us the broken tools (regardless of the manufacturer), and slugs of the material being punched. We would be glad to make a recommendations that will improve the performance, and safety, in your plant.

 

Standard Clearance RECOMMENDED Between Punch and Die

Standard die size is punch size plus clearance:

For 3/16 - 1/2" material thickness, allow 1/32" total clearance
For 1/2 - 3/4" material thickness, allow 1/16" total clearance
For 3/4 - 1" material thickness, allow 3/32" total clearance

READ AND UNDERSTAND THIS WARNING. PROTECT YOURSELF AND OTHERS WHEN OPERATING MACHINERY.

Extreme pressures are generated. Be sure that safety protection devices furnished with your machines are in place when in use. Wear safety glasses and follow all safety procedures.

Drawings and charts are for reference only.

It is the responsibility of the user to operate machines and tooling in accordance with OSHA laws and ANSI B11.5 Safety Standards.