V Notch and Corner Notch: their role in the Rectangular Duct Fabrication processes

V Notches are the bending notches on straight duct on Slip & Drive

V Notch: Bending Points

How do you bend a flat sheet of metal into a rectangle or L section if there is a profile rollformed on the two vertical edges of the Blank as it approaches the Braking Station?

You can’t…unless there is a way to remove the rollformed edge from interfering at the bending points. Notching out a V or Slot at these points prior to rollforming a profile on these two edges is the solution. The depth of this bending notch varies according to the Transverse Connection being used on the Duct. There are three methods for the transverse connection: Slip & Drive Duct, TDC/TDF, and Ductmate. The first two have a profile rollformed on the sheet’s edge and thus require a notched out area at the bending points, the third–Ductmate–is an entirely separate component and does not.

Vicon’s schematics on their Notches – both Slip & Drive and TDC/TDF

Slip and Drive duct:

Uses 1” deep V Notch to remove the drive turn hem from interfering during the bending

Slip and Drive duct requires the Notches because, even though two of the four sides of the edge are raw and elevated for the Flat S lock, the other two sides have edges with a 180 degree open hem for the drive cleat. The Notching for Slip and Drive duct is a V notch with a 1″ depth and it occurs before the drive hem is turned

Slip & Drive duct requires the Notches because, even though two of the four sides of the edge are raw and elevated for the Flat S lock, the other two sides have edges with a 180 degree open hem for the drive cleat. The Notching for Slip & Drive duct is a V notch with a 1” depth and it occurs before the drive hem is turned.

Notched in the flat, then the drive is turned, then bent into rectangular duct

TDC or TDF duct:

2” deep notch is required to remove the Flanged edge from interfering during the bending. Lockformer uses a true 2-5/8” Slot Notch. Vicon offers the V Notch with a Slot at the bending point that they refer to as a Flute Notch; the depth is adjustable so it works on both Slip & Drive Duct and TDC Duct.

TDC Duct must be notched at corners because all four sides have flanges formed onto the duct edge.

Vicon offers two variations of a V Notch for the bending points- one is a true V notch; the other is a V notch with a slot at the bending that they call a Flute Notch.

Vicon has designed their coil line notching stations so that a true V notch can be used on both Slip & Drive Duct (1” depth notched out) or TDC/TDF (2” or more depth notched out) simply by adjusting the positioning by means of those turning wheels with handles.

The operator can bring the notch heads in and out to adjust the depth of the notch for either TDC/TDF or S&D. The attached photo shows the notch head adjustment hand wheels that are located on the operator side of the coil line.

Lockformer uses a Slot Notch for the Bending Points on TDC Duct

Ductmate:

No Notch is needed because there’s no rollformed profile on the bending points

Although a minimal notch may allow easier bend on heavier gauges, no Notch is needed when using Ductmate for the duct connection. Ductmate is an entirely separate product, it’s attached to the edge of the duct once the duct completes the bending process. And it’s put on, one separate flange for each side of the duct.

Ductmate is a Slide on Frame, completely separate from the duct section it’s slid over. No profile rollformed on the edge

This is Ductmate duct; notching is not needed because it’s a slide on frame ; notching also leaves a large gap to seal

Ductmate Duct: no notching required to bend the 90 degree angle since square profile rolled on the ends

End Notches (also referred to as Corner Notch):

The purpose of the corner notches on TDC duct is so that there’s an open space at the end so that the TDC profile isn’t rollformed onto the Pittsburgh Seam. Corner notch is 2-5/8″ deep, with the other dimension varying depending on whether it’s for the Male flange or Female seam.

The corner notch keeps the Male Pittsburgh from being part of the TDF profile when rollformed

In a coil line, the 60” width approaches the Braking station horizontally. Leading the way is the female Pittsburgh Seam rollformed on the entire front edge with the Right Angle/Male Pittsburgh rollformed on the ending edge. Because these two end edges of the blank are moving horizontally thru the Braking station, they don’t interfere with the bending process. All four corners have a square notch out so that the male and female Pittsburgh (or Buttonlock) can be seamed together at the very end of the fabrication process.

The square like End Notches are used so that the Pitts Seam will not run up thru the Rolled up TDF profile

Once rollformed becomes…

End Notch for Male Pittsburgh (aka Right Angle Flange) shown in Flat

Once rollfromed becomes…

Corner notches on ends so that the longitudinal seam does not interfere with the over 2” of metal used on TDF profile

End Notch for Slip & Drive Duct will have shorter depth than TDC/F Duct

Once formed into Duct, the open spaces created by the bending Notches are filled by TDC/F Corners that serve as the means of connecting one duct section to another. The corners also fill that open space, finishing the Flange so it has a continuous run of metal on the end.

Side note:

Conklin’s Orlando branch offers contractors the unique service of Galvanized Sheets that are Blanked, Beaded and Notched. For jobs with a lot of straight duct runs, BBN is a big savings in “drop” and also in labor for the duct fab shop, who now only has to run the locks, bend and hammer together the Pittsburgh