The second-most important consideration in air
forming is the punch nose radius. You do not want a
radius on the punch nose to be larger than the natural radius floated in the part, and you do not want a
punch nose radius less than what’s known as a sharp
bend, or the minimum inside radius that’s possible
without creasing the center of the bend. For more
on this topic, check out “What makes an air bend
sharp on a press brake?” and “How an air bend turns
sharp,” both archived at thefabricator.com.
Depending on your desired inside radius, you can
use these concepts to pick the appropriate die opening and punch radius for the job. The closer you can
get the punch nose radius to the naturally floated radius, the more consistent and stable the bends will
become, both dimensionally and angularly.
Air Bend Tooling Considerations
If you’re air bending, know that the included die angle, die radius, and the radius at the bottom of the
die have no e;ect on the floated inside radius of the
workpiece, which again is a function of the die width.
That said, if you will be air forming, the 85-degree
dies you mentioned are a good choice, as long as
their widths produce your desired inside bend radii
in your workpieces, and they can handle the re-
quired forming tonnage. Know, however, that bot-
toming cannot be performed or even attempted on
these tools. Acute dies are meant solely for air form-
ing. Combining any acute-angle die with the ton-
nage pressure of bottoming would create so much
side thrust on your die that it would split your tool
down the middle.
How do you select the correct styles and profiles
for your new punch and die sets? That will be the
topic of next month’s column.
Tooling Is a Consumable
I have watched many a fabricator buy a new, state-of-the-art press brake only to continue to use the
same old beat-up tooling and outdated methods—
then question why their new, state-of-the-art press
brake isn’t living up to expectations!
Press brake tooling should always be viewed as
a consumable item; it’s long-lasting, for sure, but it
does not last forever. It wears out. The amount of
extra time your operator will spend attempting to
correct for issues directly related to worn-out tooling will far surpass the costs of new, high-quality
Along with supervisors, managers, and executives
(who may not want to spend the money), operators
and technicians are just as culpable in hindering
the adoption of new tooling, bending methods, and
“We’ve always done the job with that old tool.”
“We can’t do the job without that old tool.”
“We’ve always used it, and it can’t even be mount-
ed into the new press brake.”
Occasionally a job may require a special tool, but
you can use adapters (traditional planed to preci-
sion, or precision to traditional planed) to fit it on a
new press brake. It o;en boils down to human na-
ture and having to move out of our comfort zones.
As an industry, our mindset must change: New
tooling makes positive things happen!
at the bottom of the die
This coining setup will lead to problems. The radius at
the bottom of the die should not be smaller than the
outside bend radius.
DOUBLE SIDED PROCESSING
IN A SINGLE PASS
356 Hudson River Road
Phone + 1 518 326 9094
Deburring · Edge Rounding
With our new Eco-Line Machines
the well-known LISSMAC Edge
now starts at 69,600.
Steve Benson is a member and former chair of the Precision Sheet Metal Technology Council of the Fabricators
& Manufacturers Association International®. He is the
president of ASMA LLC, email@example.com.
Benson also conducts FMA’s Precision Press Brake Certificate Program, which is held at locations across the
country. For more information, visit www.fmanet.org/
training, or call 888-394-4362. For more information on
bending, check out Benson’s book, theArtofPressBrake:
the Digital Handbook for Precision Sheet Metal Fabrication, ©2014, available at www.theartofpressbrake.com.
The author’s latest book, Bending Basics, will be available soon at the FMA bookstore, www.fmanet.org/store.