The list below are some of the commonly asked hole punching questions with answers from our experienced staff at UniPunch Products. Our business is to provide you our high quality hole punching systems and the knowledge to operate and maintain your investment.

We invite you to contribute to this section by sending us your questions by e-mail to info@unipunch.com. Your input and suggestions are gratefully accepted.

What causes some of my punches to stick in the material after the part is punched?

There are several reasons for this condition. First, dull punches will cause the material to improperly fracture the material. This is evident by checking the burnished area on the slugs. This burnished area should be approximately 20 percent of the total material thickness.

Second, stripping springs that are worn and have taken a set will not provide full stripping pressure. The specifications for new spring lengths are listed on each unit page. Click here to see the 2140 stripping spring specification on catalog page 23. This combination of dull punches & dies and fatigued springs results in the reduced tooling performance. As a general rule, we recommend to sharpen often and take light cuts.

My press brake has limited tonnage. How do I calculate the tonnage per hole for punching stainless steel?

As an example, let’s say you need to punch .875” diameter holes in 3/16” type 304 Stainless. The formula begins the same as for mild steel:

3.1416 x .875 (Dia. Of Hole) x .187 (Mat’l Thickness) x 25 = 12.8 Tons for mild steel

Because stainless steel has a higher shear strength, a multiplier factor of 1.40 is required.

12.8 (Tons for MS) x 1.4 (Multiplier for stainless) = 17.9 Ton per hole required.

For this and other tonnage calculation formulas, click here for Technical Data page 110.

How often should I lubricate my UniPunch tooling? What lubrication do you recommend?

The basic rule is to keep the upper arm components of UniPunch tooling well lubricated and the frequency varies from each press environment. An inspection of the moving components is recommended during and after a normal shift. Some materials such as hot rolled steel or galvanized steel that create scale when punched will require additional maintenance. We recommend a light machine oil – SAE 10 or equivalent. Lubricants that contain chemical driers are not recommended.

I need to punch holes close to the edge of my 1/4” flat bar. Are there typical guidelines in order not to distort or bulge my material?

To prevent your part from distorting at the hole locations, UniPunch recommends that the punched hole be located a minimum of 1½ to 2 times material thickness from the edge of the hole. The diagram shown here depicts what can be avoided when adhering to these guidelines.