It may seem simple to bend sheet metal with a press, but myths about press brake tooling can lead to confusion and inefficiency. It’s hard to know the truth about optimal tool use. We’ll debunk 6 key myths about press brake tooling that could be slowing down metal workers and show how the truth can lead to increased productivity.
Myth No. 1: Separate tools are needed for 90deg/Offset bends
It’s not always the case. Sometimes you can modify a standard die simply by removing a small portion of the back. The same tool can be used to make two bends, one on each side, close together. This creates a space for the metal flange created by the first bend. This trick allows you to make 90-degree bends and offset bends as well as sharp (acute angle) bends.
However, there are some limitations:
- The die can only be ground back up to a certain level (where the V-shaped opening meets the flat top).
- As you bend the metal, it is pulled into dies and some material is used up. This won’t work with very small offsets, such as bending metal to its own thickness. But it works well for medium and larger offsets.
Myth #2: Never use punches or dies with different angles
This was a common belief, especially for older press brakes that were manufactured before 2000. Many machine controls would have sounded an alarm back then if the angle of the punch was greater than the V-opening angle of the die. The machine would stop thinking that the tools could crash.
The world has changed. The world has changed. The die becomes less effective if they are matched. The real question is how far can the punch tip go beyond the upper corners (shoulders), before it hits anything.
Now, the main limit is the angle of the punch tip. You can’t bend the metal at an angle less than 86° if your punch tip is 86°. This rule applies to any punch that has an angle greater than the V-opening of the die.
The ability to use dies that are designed for acute angles without having to match angles is a great advantage, especially when using dies with sharp angles. If you air bend 90 degree angles on thinner steel, stainless or aluminum (such as 10-gauge or lower), you can use punches with 86, 75, or 80-degree tips in conjunction with a 30-degree die. You can use a sharp-angle die if you need to bend angles more sharply in the future. This means you don’t have to buy a new set of dies. You can save money and time by not having to change your tools.
Myth #3: Shorter Tools Are Always Cheaper
A short punch (like a 4 inch tall one) is cheaper than a longer one (like a 6 or 8 inch taller one) at the moment. It saves you money up front. If you are a shop who makes parts for multiple customers, then you will likely need to purchase the same punch profile at a larger size in the future. When a job calls for bending an object that your small punch cannot handle, this is what happens. This is a problem that even companies who make their own products face.
If you buy a shorter punch, then later buy the taller version, you have basically bought the same tool twice. You’ve probably wasted money. Taller punches allow you to create taller or deeper parts. Consider boxes with four long sides or U-shaped channels that are deep and have long sides.
The “open height” of the press brake (the distance between the top and bottom beams) is also affected by taller punches. It is recommended that there be at least 100 mm (four inches) between the die and punch. It is easier to bend the part and then remove it. Deep parts may require more space.
Diets that are 2.165 inches tall (55 mm), work well in many situations and cost less than larger dies. You can always buy taller dies when you need them if your press brake is large enough. Make sure that you have the space to work before purchasing them.
You’ll need to buy taller dies and punches if your press brake is very high (like more than 23 inches or 600mm). When buying this type of machine, budget for the more expensive tools. These big machines combined with tall dies and punches (up to 8 inches) offer incredible flexibility.
Myth #4: You Don’t Need Coining Anymore
It’s simply not true. Modern CNC press brakes excel at “air bending”, where the punch pushes metal into the die V, but does not fully bottom out. Air bending is flexible, fast and efficient. Sometimes, however, “bottom-bending” (pushing the metal a little harder) or “coining”, (stamping very hard on the metal with matched tools), are still required.
Imagine a company who wanted to bring an old product back. They wanted to keep everything the same as it was decades ago. This included inside corners with “as sharp a bend as possible.”
Air bending tools would produce inside bend corners that are roughly the same size as the thickness of metal. The company claimed that the corners were too large! The original products were manufactured many years ago and they used tools for coining. The only way back then to achieve the accuracy and appearance required was by coining (see Figure 4).
Air bending is a great way to bend metal. Air bending is not always the best option, especially when you want to bend corners that are sharper than metal thickness. When you purchase your next press brake, keep this in mind. Think about your current customers and what you would like to attract in the future.
Compare Bending Methods
| Method | Inside Radius | Force Required | Tool Life | Versatility | Use Best For |
|---|---|---|---|---|---|
| Air Bending | Material thickness | Low-cost | Long | High-quality | Variable angles are used in most applications |
| Bottom Bending | Material thickness 0.5-0.8x | The Medium | The Medium | The Medium | Consistent bends, tighter radii |
| Coining | Material thickness 0.5x | Very High | Shortcuts | Low-cost | Precision work and ultra-sharp corners |
Myth #5 – You can’t air bend small corners (Radii).
You can, but only if you know how small the radius of the inside corner is (see Figure 5). You can air bend mild steel or soft aluminium in gauge sizes that are common. The inside corners will be almost as sharp as material thickness. This is done by using a die that has a V-shaped opening about six times larger than the thickness of the material.
As an example:
- The inside radius of 0.066 inch is obtained by bending mild steel 16 gauge (about 0.060″ thick) using a V-die of 0.394″ (10 mm).
- When bent in a V-die of 0.630 inches, a 12-gauge mild-steel (about 0.105 inch thick) has an inside radius of 0.105 inch.
Most people find an air-bent, material-thick corner quite sharp. Many companies that require sharp corners will accept air-bent corners, as they do not have to purchase expensive tools or deal with the high forces required for coining.
This method works best with mild steel or soft aluminum that is 12 gauge and smaller. It becomes more difficult with thicker metal. The outside of the bend will stretch more as the metal thickness increases. This can lead to thinning and even cracking.
Some shops bend hot-rolled metal up to 3/16 inch (0.188 inches). The V-opening should be six times thicker than the steel thickness. The key to success is using high-quality metal, and bending the metal across its grain instead of following it.
Recommended V-Die openings for Air Bending
| Material Type | Material Thickness | Recommended V-Die Width | Expected Inside Radius |
|---|---|---|---|
| Mild Steel | 16 ga (0.060″) | 0.394″ (10 mm) | ~0.066″ |
| Mild Steel | 14 ga (0.075″) | 0.472″ (12 mm) | ~0.078″ |
| Mild Steel | 12 ga (0.105″) | 0.630″ (16 mm) | ~0.105″ |
| Mild Steel | 10 ga (0.135″) | 0.787″ (20 mm) | ~0.135″ |
| Aluminium | 0.080″ | 0.472″ (12 mm) | ~0.080″ |
| Stainless Steel | 16 ga (0.060″) | 0.394″ (10 mm) | ~0.066″ |
Myth #6 You can bend almost anything with a single punch tip
People often try to cut costs on tools after spending a lot on a fancy, expensive press brake. People try to save money by using only one or a few punch sizes. It can cost you more over time.
If you repeatedly apply too much force to a radius of a punch, it will wear out much faster than usual. It is worse when you are bending materials with rough edges, such as hot-rolled metals, sheets with holes or burrs (perforated), or materials with strong materials.
When punch tips wear out, small cracks may form where the tip touches the metal (see figure 6). The cracks can spread and cause the tip to become flat. You’ll have to replace damaged punches earlier because this will affect your bending accuracy.
The following guidelines will help you choose the right punch tip radius for mild steel based on its thickness.
- To convert from 22 gauge to 11 gauge, use a PTR value of 0.030 inch. Use a PTR of 0.030 in. (about 1 mm).
- Use 10-gauge up to 1/4 inch (0.250 inches). Use a PTR 0.125 inch. (about 3 mm).
- 1/4 inch (0.250 inches) To 1/2 inch (0.500 inches) Use a PTR 0.236 inches. Use a PTR of 0.236 in. (about 6 mm).
Tool Maintenance and Care
Press Brake Tooling Myths highlight the importance of correct tool use, but also good tool care. Press Brake Tooling of high quality is best. Choose punches made from hardened steel that are precisely ground. Keep the tips clean and free of rust. The most important thing is to stay within the force limits. It is important to invest in quality press brake tooling. Quality punches can last for up to 10-12 years regardless of the workload.
Maintenance of Tools: Best Practices
- Regular Inspection : Before each use, check tools for cracks or wear.
- Cleaning Remove metal particles after each shift
- Lubrication : Apply a thin coat of machine oil in humid areas to prevent rust.
- Proper storage: When not in use, keep tools in racks and cabinets.
- Rotation : To ensure that tools are used evenly, use a rotation schedule.
You can tell if your tools need replacement by the following signs
- Cracks or chips visible on the surface
- Uneven bend angles even with proper machine setup
- Significant tool deflection during operation
- Flat spots visible on punch tips
- The presence of excessive marks or scratches in the finished product
Conclusion: The real cost of tooling myths
The truth behind common press brake tooling misconceptions can have a significant impact on your shop’s productivity. Selecting the right tool for specific applications can help you:
- Reducing setup time and changing tools
- Reduce replacement costs and extend tool life
- Enhance part quality and consistency
- Reduce material waste through rework
- Overall machine efficiency can be increased
Consider tooling an investment, not just an expense. Properly maintained and used tools will pay for themselves many times over through increased productivity and manufacturing capabilities.
Modern press brakes offer tremendous flexibility but only if they are paired with the right tooling strategy. You can unlock the full potential of your press brake by overcoming these common misconceptions and gaining a competitive advantage in sheet metal fabrication.
