Cross breaking and duct beading do essentially the same thing. Both methods are used to add rigidity to the ductwork.
The “cold air return” ductwork in your home or office is under ‘negative’ pressure—meaning that the ductwork wants to pull or suck in. The “supply (heat or conditioned air)” ductwork is under ‘positive’ pressure and wants to expand or pop out.
When the system is off, the system is under no pressure. However, when the fan or blower starts the return and supply ducts experience negative and positive pressures. This sudden pressure change will cause the ductwork to “pop or bang”. This is sometimes referred to as oil canning. If you are old like me, you will remember the old-style oil cans where you’d press the bottom of the can in to force oil out then it would pop back out again. By cross breaking or beading the duct you add rigidity to the duct and the chance of oil canning is reduced.
The noise from oil canning, albeit an irritating noise which is directly associated with a sudden change in ductwork pressure, it is not harmful to your ductwork. Cross breaking or beading simply helps to eliminates the possibility of that noise.
Shops that bead duct, whether on a standalone duct beader or a beading station on a coil line will run the metal through the beader while still in the flat before the duct is “broken up” or bent. Those shops that don’t have a duct beader will use their hand break, press brake or Roto-Die and put a slight crease or “break” in the duct from one corner to another and then they spin it and do the other corner to corner.
The two processes are very easy to recognize; cross breaking is a slight crease across each corner on each flat surface and it looks like an “X”. Beaded duct has a “bead” or half circle formed into the metal which will run around the circumference of the duct when assembled.
Standalone duct beaders are typically 5’ in length and have a series of male and female bead dies spaced 12” between centers. The shafts that the bead rolls are mounted on are powered and all the operator has to do is lay the flat duct on the infeed table and up against a side guide and with a slight push the material is pulled into the rotating shafts and in seconds it comes out the other side beaded duct work ready to be formed.
Duct beading is much faster as compared to cross breaking. Any shop that has a beader will in most cases produce beaded duct faster and more uniform that cross broken duct. Now you might say that you can cross break just as fast on your press break or Roto Die. That may be true but the cost of a duct beader is much less than a press brake or Roto Die and it uses a lot less power and has one sole purpose. A press brake or Roto Die is used for many different operations and if you are tying it up to cross break then you are creating a bottleneck in your shop. A powered duct beader will beat an operator cross breaking on a hand brake hands down every time.
Most people will say that cross broken duct is more appealing to the eyes, but when it comes right down to it beaded duct is cheaper and easier to make and most often is hidden in the ceiling and is not seen.
Beaded duct is now the accepted norm in most parts of the world and cross breaking, while still performed is far less common especially in commercial applications where the dust work most often would be made on an automated coil line.