A manual swaging tool can have either three or five blades.
Five-bladed swaging tools feature three blades on the bottom jaw, and two on the top.
A swaging tool with this number of blades is intended solely for use on round pipes.
Three-bladed swaging tools feature two blades on the bottom jaw, and one on the top.
A swaging tool with this number of blades can be used to alter the dimensions of square pipes as well as round ones.
Why shouldn’t a five-bladed swaging tool be used on a square pipe?
When swaging a square pipe to fit into another square pipe, it is important to maintain the shape as much as possible to prevent leakage – in the same way as swaging a circular pipe maintains the circular shape while decreasing the diameter.
If the shape of the pipe is altered, it will not fit as tightly into the non-swaged pipe when it comes to joining them together, as any deformed edges will reduce the surface-to-surface contact between pipes, leaving extra space open for leakage.
Were a five-bladed swaging tool to be used on a square pipe, the pressure on either side of each corner would deform it to too great an extent to maintain the shape – essentially, the force applied by two blades on the exterior of the wall and three on the interior, resulting in force being applied from inside the corner as well as outside, would increase the corner’s radius, rather than decreasing it.
Rather than the small decrease in diameter desired,the result would be a much-deformed square, making it very difficult to fit the resulting swaged pipe into the non-swaged equivalent.
When a three-bladed swaging tool is used on a square pipe, the single upper blade applies downward force to the corner, essentially ‘tucking’ it inward for insertion into the equivalent non-swaged pipe’s corners, while the two lower blades provide support to the pipe edge adjacent to the corner, preventing further deformation.
