TDC vs. TDF Profile

Lockformer's TDC Machine (circa 1975) Smacna classifies any rolled-on transverse connector as T25. Lockformer was the first to introduce a TDC Rollformer (Transverse Duct Connector), followed by Engel with their TDF Rollformer (Transverse Duct Flange). These machines rollform the flange to the end of the duct joint, meaning the duct wall and flange are one piece. TDC/TDF duct is used instead of Ductmate flange for the transverse connection (end to end) on medium and high-pressure rectangular duct systems.

How to Identify a TDC vs TDF Profile:

On TDC, the hem on the flange is on the outside; on TDF, the hem on the flange is on the inside.

Differences Between Machinery Requirements to Roll Each T25a (C) and T25b (F) Profile:

12 stations are required to form the TDC profile; 16 stations are required to form the TDF profile. The TDC machine is available as 12 or 16 station, while the TDF machine is sold only as a 16 station.

Which is a Better Profile?

Though Smacna doesn’t differentiate between the two, the T25B (F) profile is often considered a better profile because it's hemmed to the inside, adding strength and leaving no exposed edge on the outer part of the duct. There may be arguments in favor of the TDC profile, possibly as it relates to the components. Let's let the duct fab shops determine this for themselves.