Offset Duct Crimper

Klenk's Offset Duct Crimper

Sheet metal heat ducting is one of those parts of any home that is not often seen or appreciated, especially since it is buried in the attic or below the floor.  The heating and ventilation contractor that installed the ducting had to use some special tools to make all the piping fit together and the subject of this article is one of those tools.

Normal machine crimped duct end

In some places where the ducting has to fit together, the last two ends are the same diameter and will not push together.   Normally, there is a crimped end that reduces the diameter and the mating pipe has a smooth, un-formed end.  The crimped end of the first pipe is then pushed inside of the smooth end of the second pipe.  I also ran into this problem in several places when installing dust collector piping in my wood shop.  I purchased lots of fittings, connectors and different size pipes.  When I started to put the pieces together, more than a few places ended up with an un-crimped end of one pipe needing to be installed into another pipe or fitting with another un-crimped end of the same diameter.  

Five crimping fingers on tool make two creases at once

As anyone that has tried to install ducting knows, it is virtually impossible to push two ducts of the same size into each other.  Usually, one end is machine crimped to make it smaller so it will fit inside of another duct of the same size. 
The tool I used is made by Klenk Tools of Canton, OH, model number MA71260.  The working end of the crimper has three steel fingers on one half of the jaw and two fingers on the other half.  When squeezed together with the handles, the fingers pass each other. 

Crimping a piece of snap lock ducting with offset crimper

When a piece of sheet metal ducting is placed between the fingers, the sheet metal is creased in two places as the fingers pass each other.  To make a complete crimped end of the duct, the tool is squeezed repeatedly around the perimeter of the pipe until it is all crimped.  The handle is offset from from the same line as the jaws to provide more clearance for the user's hands when using in tight places. 
  
It appears this tool has been around for almost a century in various forms.  In fact, U.S. patent number 1,284,993 describes this tool very closely and was issued in 1918 to Frank Bellman of Los Angeles.  So, if you need to install some ducting and want to make the job easier this tool can be purchased online from Klenk Tools for less than $30.