5 Clear-cut Questions & Answers about Sheet Metal Punching Machines

A good sheet metal punching machine improves productivity and product quality. What is more, it reduces the punching costs. But how does a punching machine work? What can be done with it? And what is the best way to use it? Haco went looking for the most frequently asked questions concerning punching machines and came back with these clear-cut answers!

Question 1: How thick or thin can my metal sheets be?

Answer: Between 0.5 and 8 mm

Most punching machines can process metal sheets between 0.5 and 8 mm thick. However, if the sheets are made of hard materials, you need a smaller punch.

For instance, in an 8 mm stainless steel sheet, you can punch a hole with a maximum diameter of 16 mm (with 22.5 Ton punching force). By contrast, you can punch 56 mm holes in an 8 mm aluminium sheet with the same punching force.

Question 2: Do I need a separate punch for each specific form?

Answer: No, you can combine punches or use them in different angles.

You can easily combine different punch shapes. If you want to punch a keyhole, for instance, you can combine a round punch and an oval one. Naturally you might want to get a keyhole-shaped punch, depending on the number of times you need it.

If you want to use a certain shape on the same sheet in a different angle, you do not need a new punch. Thanks to our auto-indexable punching heads, you can index all the tools. This way, you need 40 to 70 % less tools!

Question 3: How many tools can a punching machine hold?

Answer: Typical between 1 and 50 (can be extended by using multitools)

Depending on the type and brand of the machine, it can hold up to 50 tools. Sometimes a few more, sometimes a few less. Thanks to auto-indexing, however, you don't need that many! You can use the same tool in several ways. This way you can do the same things you can do without auto-indexing, but with only 30 % of the tools.

Question 4: How much punching power do I need?

Answer: F= (t*C*S)/1000

The thickness of the sheet metal X  the outer circumference of the punch X the shear strength of the material, divided by 1000.

In a formula: F= (t*C*S)/1000

• F: the necessary punching power in ton
• t: sheet thickness in mm
• C: the outer cicrumference of the punch in mm 
• S: the shear strength of the material in kg/mm². In practice, this is about 80 % of the tensile strength. For a safer calculation, often the tensile strength is used.

Question 5: How long do punching tools last?

Answer: Between 50.000 and 9.500.000 hits

Some Punching tools can last up to 9.500.000 hits . Their lifespan can however vary significantly, depending on different factors, such as the material that is punched, its thickness, the nibbling step, tool steel, type of tool coating and tool maintenance.

Some rules to remember:

• Punches from high-grade steel (e.g. powder steel), with extra coating or with automatic air blow or oil mist lubrication have a longer life.
• The harder and the thicker the material you are punching is, the sooner your tools will wear off.
• Frequent sharpening adds 50 % to your tool's lifespan.
• The nibbling step(*) in nibbling operations can never be smaller than the sheet thickness.
• And the overlap (**)ratio in slitting  operations should never be bigger than 20%

Want to know more about punching machines? Check out Haco's range of punching machines or visit our showroom.