How to Build HVAC Ducts

Making your own HVAC ductwork is a process that involves metal fabrication machines, as well as knowledge of how to safely use the machines. Although many sizes and shapes of ducts are sold at home improvement stores, it is sometimes necessary to make your own, especially if you have a unique size or application for the ductwork. Often, HVAC firms have a set of trained employees that make the ductwork they need.

Sheet metal stock
Measuring tape and straightedge ruler
Leather gloves
Metal shearer
Metal break
Metal lock former
Sheet metal hammer

Instructions

- 1
  Mark the completed length and width needed for a rectangular duct on the sheet metal. Add 1 ¼ inches to the width mark. This extra 1 1/4 inches will be bent and locked together later.
- 2
  Mark where to bend the sheet metal for each side of the duct. For instance, if you need a piece of duct 6 by 4 inches, you would have marks for a bend at the 1-inch mark, then a mark at 6 inches, then 4 inches, then 6 inches, then 4 inches, then ¼ inch.
- 3
  Cut the metal to length first. Slip the metal into the shear and line up the mark with the blade. Lock the metal into place and cut off what you do not need.
- 4
  Place the metal into the lock former. Slide the edge with the extra 1-inch measurement into the former. Activate the machine. Remove the metal and go on to the break to make the bends.
- 5
  Slide the metal into the break and line up the marks for the first bend. Set the machine for a 90-degree bend and activate the machine. Repeat this until all the bends are made and you have formed a rectangle.
- 6
  Slide the extra ¼ inch of metal into the lock that was previously made. Pound the duct with a sheet metal hammer to close the lock and secure the seam of the duct.

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