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Thread: Cutting Black Iron Pipe

  1. #1
    DIY Member tonyn1's Avatar
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    Default Cutting Black Iron Pipe

    I'm replacing my black cast iron sewer drain pipes with PVC as I'm remodeling and adding new fixtures. The iron pipe comes into the house and I don't want to go to the expense of replacing that part. I want to transition to the PVC about a foot or so above where it comes into the house. My question is on cutting the iron pipe. I'd heard from several people that I need a chain cutter to do this. I even found one at a local tool rental store. It is a Ridgid 32900 model and I was all set to rent it when the guy at the rental told me it does not make even cuts, but just basically breaks the pipe, which may not come out too even. This would be a problem as I need a straight cut to install a Fernco to transition to the PVC. Is this guy off the mark on the use of this tool, like I suspect? If so, do I just tighten it and then turn it around the pipe like a regular pipe cutter? Are there other ways to do this, like a saws-all or cut-off wheel that might be easier?

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    In the Trades Tom Sawyer's Avatar
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    Sometimes a wheel cutter will shatter the pipe or make a pretty crappy cut so, if you need a nice clean cut (and you do) try a diamond wheel on a 4" angle grinder.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    In the Trades Gary Swart's Avatar
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    The angle grinder will do the job, but do it with this in mind. Unless the grinder is a very small one, the torque can be unbelievably strong. Often the blade will bind in the cut and the grinder will twist out of your hands. I have a couple of scars on my wrist where I learned this several years ago. Hurts like a bitch! If you have a 4-1/2" grinder, the torque is a lot less, but the blade will still bind. You may already know the connectors you must use are the no-hub type and not just the neoprene sleeve with 2 hose clamps.

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    Plumber Winslow's Avatar
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    If the pipe is in good shape then it should snap ok. The key to getting a good snap is having the cutters adjusted properly. To get a clean snap make sure the wheels on the cutter are square to the pipe all the way around. Spray the cutter wheels with WD40 before snapping the pipe, then use the grinder to cut off any jagged pieces. If the pipe you are snapping is vertical then it will most likely snap ok. If the pipe is horizontal then just go with the grinder with a metal cutting wheel.
    Last edited by Winslow; 11-09-2011 at 12:03 AM.

  5. #5
    Moderator & Master Plumber hj's Avatar
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    A good snapper will cut the pipe square and smooth enough for the coupling. If it didn't how would we ever cut pipes and assemble them for drain installations? You do NOT rotate the cutter, you just put pressure on the chain until the pipe snaps, which is why they are called "snap cutters".
    Licensed residential and commercial plumber

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    DIY Senior Member Rich B's Avatar
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    I made some cuts on 4" cast iron and used a sawzall with the blades they sell for cutting cast iron.

    Takes a while but the cut is perfect if you keep your saw lined up right.

    I used shielded couplings to transition to PVC and needed the couplings with different I.D.s made for copper to PVC to get a good fit.

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    DIY Member tonyn1's Avatar
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    I guess I'll try a couple cuts on a section of the pipe that is not critical.

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    DIY Member tonyn1's Avatar
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    Quote Originally Posted by Gary Swart View Post
    The angle grinder will do the job, but do it with this in mind. Unless the grinder is a very small one, the torque can be unbelievably strong. Often the blade will bind in the cut and the grinder will twist out of your hands. I have a couple of scars on my wrist where I learned this several years ago. Hurts like a bitch! If you have a 4-1/2" grinder, the torque is a lot less, but the blade will still bind. You may already know the connectors you must use are the no-hub type and not just the neoprene sleeve with 2 hose clamps.
    What are the no hub type and where can I get one?

  9. #9
    In the Trades Tom Sawyer's Avatar
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    More commonly called a mission band coupling and you want to use them because there is a slight difference of pipe diameters and the mission band compensates for that. any plumbing supply house should have what you need.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    Retired Defense Industry Engineer jadnashua's Avatar
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    If the CI pipe has a lot of internal corrosion, it may shatter if you try to snap it. If it does, it should probably be replaced anyway, though. Otherwise, the snap cutter is LOTS quicker than other means of making a cut. Just don't try to cut off a small bit - use it in the middle of a run, not right at the end.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member tonyn1's Avatar
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    I've been cutting the pipe with a cut-off wheel on an angle grinder and it works quite well.

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    Illinois Licensed Plumber SewerRatz's Avatar
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    I have been using snap cutters to cut all my cast iron pipe for 25 years, my father used snap cutters for 40+ years. 99% of the cast iron we cut snaps just fine. There is % where the pipe is to brittle and will crush, but if that is the case, the rest of the pipe needs replacing. I just did, a job where the cast iron has been underground for the last 50 years, with tons of chemicals running though it. The snap cutters cut this pipe with ease.

    As others said the key is to have it square on the pipe, well luburcated wheels and chain. As long as you have that it will cut your pipe nice and clean... Snap cutters work great on clay sewer tile as well. I always get a chuckle when I see guys out there busting thier arse with a grinder.

  13. #13
    DIY Member tonyn1's Avatar
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    Quote Originally Posted by SewerRatz View Post
    I have been using snap cutters to cut all my cast iron pipe for 25 years, my father used snap cutters for 40+ years. 99% of the cast iron we cut snaps just fine. There is % where the pipe is to brittle and will crush, but if that is the case, the rest of the pipe needs replacing. I just did, a job where the cast iron has been underground for the last 50 years, with tons of chemicals running though it. The snap cutters cut this pipe with ease.

    As others said the key is to have it square on the pipe, well luburcated wheels and chain. As long as you have that it will cut your pipe nice and clean... Snap cutters work great on clay sewer tile as well. I always get a chuckle when I see guys out there busting thier arse with a grinder.
    Actually, it cuts pretty easy with the grinder and cut-off wheel. I might have tried a snap cutter if I had one, but I would have had to rent one. Not a big expense, but I already had the grinder and it works well. Plus I need to do this without taking the chance of crushing the pipe. I am cutting the cast iron line coming in the house, and if I had to replace that, it would be major expense and hassle.

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