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How to Crimp Ducting Together

Connecting round duct work correctly allows air to efficiently flow through an air conditioning system. Assembling duct connections by crimping and inserting the crimped end of the pipe into a non-crimped duct end eliminates the need for duct couplings. Couplings have a diameter slightly smaller than the pipe diameter. When air passes by an installed coupling, it contacts the fitting, causing turbulence. This reduces the efficiency of the duct system, increasing your heating and cooling bill.

Crimp Ducting Together

Push the release button located on the forward portion of a five-blade crimper down to release the crimper handles.

Slide the open jaws of the crimper over one end of round duct pipe. Pull the handles together firmly to place a crimp on the end of the pipe. Move the crimper to align the last blade of the crimper with the lower section of the previous crimp. Repeat the process -- rolling the pipe as needed -- until one end of the pipe has a continuous crimp around its circumference.

Slide the crimp end inside a non-crimped end of duct until the depth of crimp rests inside of the other pipe.

Secure the crimped connection by running one #10 self-tapping sheet metal screw through the connection every three to four inches with a screw gun and a 5/16 inch hex head adapter.

Apply duct sealer to the screwed connection with a paint brush. Allow the duct sealer to cure for 24 hours before using the air conditioning system.

Things You Will Need

  • Five-blade crimper
  • #10 self-tapping sheet metal screws
  • Screw gun with 5/16-inch hex head adapter
  • Duct sealer
  • Paint brush

Photo Credits

  • Jupiterimages/Photos.com/Getty Images