I would like to reduce the diameter of an iron (welded) pipe without bending to the side, where the weld is. With the usual procedure, the result is as follows:

enter image description here

I am using the usual pipe reducing machine, like this one:

With my understanding, the problem is because of the weld, which is slightly softer than the rest of the pipe. When pipe is reduced, the pipe is bend towards the weld.

What I would like know exactly is: how to reduce a welded iron pipe in such way that the reduced part is completely aligned with the rest of the pipe (in a picture above, this isn't the case, as shown with a straight piece of iron bar next to the pipe)? For example, when using seamless pipes, the reduced part is not bended to any side, but I want to know the solution for the welded pipes.

  • $\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$
    – Community Bot
    Commented Nov 10, 2022 at 10:20
  • $\begingroup$ @Rob The inner weld goes horizontally with the pipe (it's where the pipe, when manufactured, is welded together). What I seek is the reducing part not leaning towards any side, but beeing completely straight (not like in the post picture), aligned with the non reduced part. I am using the usual pipe reducing machine like this one: sc04.alicdn.com/kf/Hb8c0cd9be285482e889b2cc1cc799795s.jpg $\endgroup$
    – osemec
    Commented Nov 10, 2022 at 10:41
  • $\begingroup$ Thanks for editing your question. I believe that machine is a "hose crimper" as opposed to a "pipe reducer": i.sstatic.net/X9LAy.png in any event, reduce the pipe part way then rotate 180° and finish the job; resulting in equal deflection bending it straight: info.viega.us/blog/how-to-avoid-deflection-when-pressing $\endgroup$
    – Rob
    Commented Nov 10, 2022 at 12:10

1 Answer 1


It looks like the girth weld must be ground flush with the surface before using the swage.


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