[tom_poconos]

Hi, I'm trying to figure out the ideal TPI for a large (4" nominal) cast iron pipe. As I understand it 18 and above if for thin metal, 6 and below is for wood. There are combined 10/14 TPI blades - would this be the best choice? Or would a single 8 TPI or 10 TPI be better? I don't need a smooth cut, I just need to cut through the bastard as fast as possible before my weak sawzall battery dies :laughing: Thanks for any advice!

 

[BayouRunner]

You don’t want any of the so called cast iron cutting blades with teeth. You don’t have enough batteries, they work terrible. Lennox makes a pretty good blade. You want one with grit on the edge. They are expensive but so worth it. You can spend $30 on a 5 pack with teeth and still not have the pipe cut. Or you can buy one blade with grit and make several cuts. One blade is about $10.


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[tom_poconos]

You want one with grit on the edge.

Ok thanks, i'll look for grit coated. Can you comment on the correct Teeth per Inch? I believe the cast iron will be roughly 3/8" thick but I don't know for sure.

 

[Bud9051]

The old school advice I have always followed is to be sure you have 3 teeth in the cut. Obviously thin metal can't meet that but as many teeth as possible.

The problem with the pipe you are cutting is the cutting surface starts out very wide and shrinks as you begin to cut just the wall thickness.

But I agree with Bayou, a good grit blade will do best.

Bud

 

[tom_poconos]

...have 3 teeth in the cut

Thanks - if the material is ~3/8" I'm guessing I need at least 10TPI, 8TPI might "not cut it" so to speak. I'll go for a 10/14TPI combo blade with the carbine/grit fanciness.

The other problem I face is the pipe is about 1" off a wall. I looked into renting an in-place ratcheting pipe cutter but I don't think the chain can fit behind, and the force at which the pipe splits apart seems really jarring and risky for existing joints in the pipe network.

 

[Bud9051]

Just a note, corrections welcome, but the blades with grit do not have teeth.

Bud

 

[tom_poconos]

Just a note, corrections welcome, but the blades with grit do not have teeth.

Bud

Ok, I see. They don't pop up much in searches. I found one. Thanks for clarifying.

Dang, a reviewer said it will take about 20 minutes to get through a 4" pipe with it. That definitely exceeds my sawzall battery.

I'm wondering if it might be better just to sacrifice a pack of toothed blades, I think they may cut quicker - and wear out faster (which is fine). The higher TPI blades cut slower but smoother, and a grit blade must be equivalent to a 32 TPI blade.

 

[Bud9051]

That's why I have both, corded and battery. I have corded tools that are 50 years old and still working. In less than that time (they didn't have battery tools back then) I have gone through many battery powered tools, usually because the blasted batteris are either not available or too expensive.

Bud

 

[joecaption]

It would be far faster and a straighter cut if you just rent one of these.
https://www.homedepot.com/tool-truck-rental/Ratchet-Soil-Pipe-Cutter-6/69982/index.html
I've cut many a cast pipe with these and most often I'm done cutting in less the 2 min. and it snaps off nice and clean.

 

[Ghostmaker]

Make sure you have the cast iron fully supported so it doesn't fall on you.

 

[bfrabel]

It would be far faster and a straighter cut if you just rent one of these.
https://www.homedepot.com/tool-truck-rental/Ratchet-Soil-Pipe-Cutter-6/69982/index.html
I've cut many a cast pipe with these and most often I'm done cutting in less the 2 min. and it snaps off nice and clean.

The OP says he only has 1" of space behind the pipe so he doesn't think a chain cutter would work, Although I'm betting it probably would.

If you are going with a sawzall, I agree with the advice for the special cast iron blades like the one pictured above. I don't know why, but cast iron is a bit¢h to cut compared to regular steel.

Probably not much help at this point, but if you are in the market for a new sawzall, get one with "orbital action" (or as Milwaukee calls it, a Super Sawzall). Most only have back and forth action. It actually makes a pretty big difference on how well the tool works.

 

[tom_poconos]

It would be far faster and a straighter cut if you just rent one of these.
https://www.homedepot.com/tool-truck-rental/Ratchet-Soil-Pipe-Cutter-6/69982/index.html
I've cut many a cast pipe with these and most often I'm done cutting in less the 2 min. and it snaps off nice and clean.

I've looked at renting one but I don't think the chain will fit around the back (it's less than 1" off a wall). Based on the videos I've seen of these things they produce a pretty violent lateral movement in the pipes when it splits - I don't want to risk dislodging cast iron hubs nearby.

 

[bfrabel]

An angle grinder with a thin cut off disc works pretty good too, although it sounds like you might not have enough room to cut all of the way around the pipe, unless you use a pretty large wheel (maybe 9"?). If you try this, be careful because they can be a bit dangerous if you haven't had much practice with one.

 

[BayouRunner]

Best sawzall blade TPI for 4" old cast iron pipe?

Make sure you have the cast iron fully supported so it doesn't fall on you.

This is exactly what you need. It won’t take too long. We had to cut a few on a job a couple weeks ago. They work well. Forget the blades with teeth. 100 percent waste of time and money. The blade with teeth is not going to cut your cast. Well maybe with an electric one and an hour or so of cutting. I’m not exaggerating, it does not work
I’m guessing it took him about 5 to 10 minutes to cut through 3 inch cast. I wasn’t really paying attention to the time but it wasn’t long.

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[tom_poconos]

I have come to a final decision - I know you're all recommending the grit blade but I took in to account three new pieces of evidence:

1) Multiple grit blade reviews mention how long the cuts take - the blade may last longer and do more future work than other blades but it is painfully slow.

2) One particular carbide tooth blade on Amazon (Diablo extreme metal cutting) has tons of customer photos of cast iron pipes sawed in half.

3) The video below shows the Diablo carbide tooth blade cutting through an 8" cast iron pipe with a battery sawzall in one minute...

Video


Really appreciate your help guys but I'm going to go against the advice here and go with carbide teeth. I'll still get the grit blade as a backup if the carbide tip turns out to be snake oil... wish me luck?

 

[BayouRunner]

Best sawzall blade TPI for 4" old cast iron pipe?

Let us know your final result. And some of those grit blades don’t work real well


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[tom_poconos]

Re: Best sawzall blade TPI for 4" old cast iron pipe?

Let us know your final result.

All done - took about 5 minutes. I think if I did it again I could do it 2 minutes as I fiddled around a bit (battery sawzall died FAST... switched to corded sawzall, realized halfway through upping the speed and applying more downward force helped a lot). The blade is a demon - can't speak for its future cutting efficiency after this cut but it blazed through that pipe.

 

[BayouRunner]

Thanks for the feedback. Always good to know another way!

 

[Bondo]

Thanks for the feedback. Always good to know another way!

Ayuh,..... That's the 1st I've seen of the carbide teeth sawzall blades,.....

Sorta like my 14" dry cut chopsaw,.... carbide teeth,....

 

[BayouRunner]

Best sawzall blade TPI for 4" old cast iron pipe?

That’s the first I’ve seen as well