Seen one used, and it seemed to work fine. They wound it up with a impact airgun to make a custom joint between two pieces of tube the same diameter so one would slip over the other.
Ive often thought about buying one for 2am emergencies, but it also strikes me that its something I should make for myself...
We used to have one when I was a mechanic, I could never get on with it. Like Shenion says, they need a hell of a lot of force to expand the tube. Should work ok if you heat the tube but then you might knacker the springs. I've got a feeling ours used to have a round shaft with a flat on it so you could only use it with an open ended spanner.
It’s a valuable point, that reference is made here to the force needed to use this tool. I was imaging using one “in situ” laying under the car, and by hand not air-assisted. I guess if the pipe was held in a vice & warmed up there would be some chance without air.
When I saw the tool, I was thinking about cutting out a corroded section and inserting a good piece of pipe. I felt the “over-laps” would be easier to weld than a metal patch on a pipe.
In my naivety, I thought the tool would make a repair to a corroded exhaust easier. Thank you for putting me right before I learnt the hard way.