How do I convert a 4" pipe to 3 1/2" pipe and how do I cut it?

[ken2400]

I have a 4" pipe in the ground I need to cut and convert to a 3 1/2" pipe.

Should I use a angle grinder or recip saw?

Thanks

 

[primestar31]

Shove a 3.5 inch pipe down the middle of it, with some sticking out the top for the smaller mount. Then either cross-drill and bolt, or get somebody to weld it around the join.

 

[KE4EST]

I'll add that I use my Sawzall to cut pipe with, nice and clean and easy.

 

[mikekohl]

I'll add that I use my Sawzall to cut pipe with, nice and clean and easy.

\

Tape around the 4 inch od pipe so that you can follow the line around and still be alignment with the other side. I find that an angle grinder cuts faster and is easier to remove slag with. If you use a Sawzall, melt paraffin wax on a new cutting blade when starting a cut. Touch the warm blade to the wax to keep it lubricated. This keeps the blade sharper and it will cut faster.

 

[lfp302]

Whether using sawzall, or cut-off wheel with grinder, have someone apply a push to the pipe to keep it's weight from squeezing and jamming the cutter.