Squaring up the ends of used heavy duty spiral pipe

[Bobby Robbinett]

So I decided to use spiral pipe in my new shop and most of it I ordered from The Blast Gate Company. The trunk line is 12” and I have two branches that are 10” because I was given some old 10” spiral pipe that came out of a factory. It’s very heavy and much thicker than the other pipe that I ordered. My problem is that this thick, heavy 10” spiral pipe has buggered up ends. I can’t get my fittings to go on because the ends are not perfectly round.

So my question to you guys is how can I cut the ends of this stuff to make it smooth and round? It’s obviously too big for an abrasive chop saw and too thick to cut with tin snips. I have a machine/fabrication shop down the road that might be able to help but they are backed up for several months. I don’t know if I could do it with a grinder or a sawzall? I do have a friend with a Milwaukee circular metal cutting saw (looks like a Skillsaw but for metal) that I could buy a new blade for and try it. Any suggestions?

[Larry Frank]

I would carefully mark it to get it square. I would use an angle grinder with abrasive wheel to cut it. Must be a huge dust collector to use such big pipe.

[Thomas Wilson]

I found that a jigsaw with a metal cutting blade worked best. I marked an accurate, square line with a Sharpie and cut to the line. A wide strip of something flexible like poster board can be wrapped around the pipe to get a square line for the mark. You need a 1/2 inch starting hole to insert the blade. A round file on the inside and flat file on the outside smooth the edges. I also used a cradle made of 2x6 v-blocks screwed to plywood to hold the pipe steady. It was not as big a deal as I expected it would be. A jigsaw throws a spray of metal flakes upward toward your face so snug fitting goggles are necessary.

[Jack Frederick]

Getting the pipe back to round can be done, but depending upon how heavy the gauge may require a lot of muscle. Lighter material can be shaped with some long hose clamps. You may be able to cut some plywood halves in the correct diameter and shape it from a round inner section out to the end. I use a Wrap-Around to mark pipe. It may be tricky on corrugated. You may be able to use a laser and a marker to follow the line. this is one of those spots where I love my plasma machine, but with care any of the other methods will handle the pipe.

[Malcolm McLeod]

... I love my plasma machine, ...

+1 :: rent/buy/borrow a plasma arc cutter. Make a cradle to spin the duct and then hold the cutter on your line; 30sec/end.

[Kevin Jenness]

I mark a square cut with a paper strip, cut with a jigsaw and debur with an angle grinder. If the pipe end is distorted or too small you can pull it more round with a strap clamp or expand the opening with a hammer and dolly or anvil.

[Jim Becker]

In addition to the methods mentioned, a powered (electric or air) nibbler is another choice

[Bill Dufour]

Would an oscillating tool cut this?
Bill D

[Rob Beaupre]

I found that a jigsaw with a metal cutting blade worked best. I marked an accurate, square line with a Sharpie and cut to the line. A wide strip of something flexible like poster board can be wrapped around the pipe to get a square line for the mark. You need a 1/2 inch starting hole to insert the blade. A round file on the inside and flat file on the outside smooth the edges. I also used a cradle made of 2x6 v-blocks screwed to plywood to hold the pipe steady. It was not as big a deal as I expected it would be. A jigsaw throws a spray of metal flakes upward toward your face so snug fitting goggles are necessary.

This is almost word for word how I did mine, all the way down to using a file (flat on one side, round on the other). I used a thick rubber FERNCO, 6" in diameter that I sliced lengthwise, that it can then easily be wrapped around the pipe you're cutting, and used the worm clamps to tighten it in place (making sure it's square). This gave me a 3/8" thick edge for the jig saw to ride against. Ferncos of that size aren't cheap so not sure if that is cost effective for you but I was installing my entire duct work so I was okay with the extra expense. And I too can't stress how important safety glasses are here...as recommended by Thomas.

[Frank Pratt]

Would an oscillating tool cut this?
Bill D

That would be far down the list for me. Jigsaw works very well.

[Frank Pratt]

I found that a jigsaw with a metal cutting blade worked best. I marked an accurate, square line with a Sharpie and cut to the line. A wide strip of something flexible like poster board can be wrapped around the pipe to get a square line for the mark. You need a 1/2 inch starting hole to insert the blade. A round file on the inside and flat file on the outside smooth the edges. I also used a cradle made of 2x6 v-blocks screwed to plywood to hold the pipe steady. It was not as big a deal as I expected it would be. A jigsaw throws a spray of metal flakes upward toward your face so snug fitting goggles are necessary.

That's exactly how I cut my spiral duct. Fast, easy and accurate. Set the jigsaw to a lower speed for cutting metal than you would for wood.

[Tom Dixon]

I made a roller jig out of plywood and cheap fixed castors from Amazon and used a metal cutting circular saw I bought from Eastwood. It worked great. I used it for dozens of cuts on 10" and 6" spiral pipe.