What Blade Do I Use to Cut Cast Iron? A Straight Answer on Reciprocating Saw Blades

Cast iron has a reputation, and it earns every bit of it. It's brittle, it's dense, and it does not care how sharp your blade looked in the package. Drop a standard wood blade into a cast iron pipe and you'll hear it scream, smell it burn, and watch the teeth go bald in about thirty seconds. If you've ever asked yourself "what blade do I use to cut cast iron," you're not alone, and most reciprocating saw blades on the market were never designed for this fight in the first place. Not all reciprocating saw blades are created equal, and cast iron is exactly where that difference shows up fast.

The good news: once you understand what's actually happening at the cutting edge, the answer gets a lot simpler. This guide breaks down exactly which reciprocating saw blades can stand up to cast iron, why most off-the-shelf options fail halfway through, and which EZARC blade was built specifically for this exact job.

Why Most Reciprocating Saw Blades Fail on Cast Iron

Cast iron isn't like mild steel or aluminum. It has a high carbon content, which makes it hard and abrasive but also brittle. That combination is brutal on a cutting edge. A standard bi-metal blade, the kind most people grab off a hardware store shelf, has teeth made from high speed steel welded to a flexible steel back. That works great on wood, drywall, and thin sheet metal. It does not hold up on cast iron pipe, cast iron fittings, old radiators, or engine blocks.

Here's what happens instead. The teeth heat up fast because cast iron doesn't conduct heat away from the cutting edge efficiently. That heat softens the steel teeth. The abrasive iron particles grind those softened teeth down within a few strokes. You end up with a blade that still looks fine but cuts nothing, and a job that takes three times longer than it should. Most reciprocating saw blades sold for general use were simply never engineered with cast iron in mind, and that gap is exactly where frustration (and busted blades) piles up.

What Actually Cuts Cast Iron: The Two Things That Matter

Two factors decide whether a blade survives cast iron or dies in it: tooth material and TPI (teeth per inch).

Tooth material. Carbide is the answer here. Carbide-tipped teeth are individually welded and precision-ground from tungsten carbide, a material far harder and more heat resistant than the high speed steel used in standard bi-metal blades. Carbide holds its edge against abrasive, brittle metals like cast iron in a way ordinary steel simply cannot.

TPI. For cast iron and other thick metal, you want something in the 8 to 10 TPI range. Lower TPI blades have bigger gullets between the teeth, which clear debris faster and resist clogging. Higher TPI blades, the 18 to 24 range, are built for thin sheet metal, not thick castings. Run a high TPI blade through cast iron and you'll pack the gullets full and stall the cut almost instantly.

Put carbide teeth and an 8 TPI design together and you've got the formula for a reciprocating saw blade that can actually handle cast iron without flinching. Not every blade on the rack is built to those specs, which is exactly why so many reciprocating saw blades stall out on the very first cut.

The Blade We Built for This Exact Job

This is where the EZARC 8 TPI Carbide Reciprocating Saw Blade earns its keep. We engineered it specifically for thick metal, cast iron, and high-alloy steel, the materials that chew through ordinary blades for breakfast. Out of everything on the market, this is one of the few reciprocating saw blades actually designed from the ground up for this job rather than adapted from a wood blade and hoping for the best.

A few things set it apart from the bi-metal blade sitting next to it on the shelf:

Carbide technology that lasts up to 50x longer. Every tooth is individually welded and precision-ground for impact resistance and flexibility, even under heavy, repeated cutting. That's not a small upgrade. It's the difference between swapping blades every job and swapping blades every season.

An 8 TPI design built for thick material. This blade is optimized for cutting metal between 3/16 inch and 1/2 inch thick, which covers most cast iron pipe, fittings, brackets, and structural pieces you'll run into on a job site, in a basement, or under a sink that's seen better decades.

A universal 1/2 inch shank. It fits Milwaukee, Bosch, DeWalt, and most other major reciprocating saws without an adapter, so you're not stuck hunting down a brand-specific reciprocating saw blade just because of the shank style.

Two length options. The blade comes in 6 inch and 9 inch versions, so you can match blade length to the depth of your cut, whether that's a tight plumbing access point or a wide-open demolition job.

If you've been comparing reciprocating saw blades for cast iron and feeling like every option either dulls instantly or costs as much as the saw itself, this is the middle ground: carbide-level performance without the big-brand markup.

How to Cut Cast Iron Without Wrecking Your Blade (or Your Back)

Having the right blade is half the job. Technique is the other half.

Let the carbide do the work. Don't force the saw. Pushing too hard builds heat and can chip carbide teeth, which are hard but more brittle than steel teeth. A steady, moderate feed rate cuts faster in the long run than muscling through.

Support the pipe or fitting. Cast iron is brittle, so vibration and unsupported weight can crack it unpredictably mid-cut. Clamp it down whenever you can.

Keep the blade straight in the cut. Twisting a blade sideways in cast iron is one of the fastest ways to snap a tooth clean off.

Let the blade clear its own chips. This is part of why 8 TPI reciprocating saw blades work so well here. The bigger gullets give cast iron's gritty, abrasive debris somewhere to go instead of packing into the teeth and grinding the edge dull.

Wear eye and hand protection. Cast iron throws hot, sharp particles when it's cut. This one's not optional, ever.

Carbide vs. Bi-Metal: The Quick Version

Both categories of reciprocating saw blades have a place in a toolbox, but cast iron narrows the choice down fast. If you're still deciding between carbide and bi-metal options for your project, here's the short version. Bi-metal blades cost less up front and work fine for wood, drywall, thin metal, and the occasional embedded nail. Carbide blades cost more per blade but cut cast iron, rebar, hardened steel, and high-alloy material that would turn a bi-metal blade into scrap metal in a single pass. If cast iron is even an occasional part of your work, carbide pays for itself the first time you don't have to stop and swap a dead blade halfway through a cut.

Quick FAQ

Can a regular Sawzall blade cut cast iron? Technically it can start a cut, but most standard bi-metal blades will dull or burn out before finishing anything thicker than a thin wall. Carbide is built for this material.

What TPI is best for cast iron pipe? 8 TPI is the sweet spot for most cast iron pipe and fitting work. It balances an aggressive cutting speed with enough gullet space to clear debris.

Are carbide reciprocating saw blades worth the extra cost? For cast iron, rebar, and hardened steel, yes. Carbide reciprocating saw blades cut these materials cleanly instead of grinding to a halt, and they last long enough to offset the higher upfront price fast.

Will carbide blades fit my existing saw? Most carbide reciprocating saw blades, including this one, use a universal 1/2 inch shank that fits the major brands without any modification.

The Bottom Line

Cast iron isn't impossible to cut. It just demands the right tool for the job. Skip the bi-metal blade you've already burned through twice, and reach instead for reciprocating saw blades actually built for hard, brittle, high-carbon metal: carbide teeth, 8 TPI, and a shank that fits the saw you already own.

If you want to see the full lineup of carbide and bi-metal options for every material you cut, browse the complete collection of reciprocating saw blades from EZARC. And if you're still sorting out TPI, tooth design, or blade length for a different project, our full breakdown on how to select the right Sawzall blade walks through every variable so you never have to guess again.

Cast iron won't soften. But with the right blade, your next cut just got a whole lot easier.