Bosch Diamond-grit reciprocating saw blade

Why I reached for this blade

I’ve cut my share of cast iron stacks and trimmed more than a few concrete blocks for renovation open-ups. In tight, occupied spaces—especially basements and bath alcoves—an angle grinder is fast but messy, loud, and spark-happy. That’s where a diamond-grit reciprocating blade earns its keep. Bosch’s diamond-grit blade, in a 9-inch length with a 50-grit edge, is purpose-built for abrasive materials like cast iron and CMU block. I put it to work on a few real tasks: cutting out sections of 4-inch cast iron soil pipe, trimming a cast-iron tub, and nibbling a notch in a concrete block wall for a conduit.

Setup and compatibility

The blade drops into any standard reciprocating saw. It’s a continuous abrasive edge, so there are no teeth to orient; you can run it either direction. I had the best results with orbital action off and a moderate stroke rate. On my corded saw, dialing the trigger to the mid range was the sweet spot—fast enough to keep swarf clearing, slow enough to avoid glazing the diamonds.

At 9 inches, the blade gives good reach around larger diameter pipe and makes it easier to start flush cuts. It’s sold individually, which matters for budgeting; diamond-grit blades cost more per piece than standard bi-metal, but they’re aimed at jobs bi-metal just doesn’t handle well.

Cutting cast iron: steady, controllable progress

Cast iron is where this blade earns its reputation. Compared to carbide-tooth recip blades, the diamond edge is less grabby, which makes it easier to control your line without chatter. On vertical pipe, I scored a shallow track around the circumference first, then worked gradually through. A pipe strap to keep the section from collapsing onto the blade is worth the minute it takes to install.

Speed-wise, you won’t confuse this with an angle grinder, but the progress is consistent. On 4-inch pipe, I’d call it a few minutes per cut with minimal drama. The edge doesn’t throw sparks and keeps burrs manageable. Heat buildup was noticeable only when I pushed too hard; easing pressure and letting the abrasive do the work kept it running cooler and actually sped things up.

I also used it on a cast-iron tub to open a drain cutout. The control was a plus there: the blade tracked well without skittering across the enamel. Expect more time on thick tubs, but the edge stayed effective from start to finish.

Concrete block: practical for small cuts and adjustments

For CMU, I treat a reciprocating saw as a finesse tool rather than a primary cutter. This blade excels at creating notches, enlarging openings, and cleaning up grinder cuts without kicking up a storm of sparks. It prefers a scored path: I scribed a shallow kerf, then stepped the blade in gradually. It’s slower than a diamond wheel in a grinder, but cleaner in close quarters and easier to use near wood framing, wiring, or plumbing where sparks and overcuts are risky.

Debris clearing was adequate, helped by the blade’s segmented, “turbo” edge profile that opens small channels for dust to escape. You still need a vac nearby; CMU dust is unavoidable, just reduced compared to a grinder.

Cut quality and control

• The continuous abrasive edge reduces snagging and kickback on brittle materials. That’s especially helpful overhead or on free-hanging pipe.
• Kerf width is thin and consistent, leaving a neat cut line on pipe and a tidy notch in block.
• The blade rides well in curved tracks. For anyone cutting around fixtures or making inside corners in block, that predictability is useful.

Durability and wear

Diamond grit shines on abrasive materials because it resists rounding and dulling better than carbide when rubbing through porous, granular surfaces. Across several cast-iron cuts and a handful of CMU notches, the edge kept biting. If you feel it slowing, it can be due to glazing—too much heat or pressure can smooth over the diamonds. Backing off the speed, reducing feed pressure, and cutting a few inches into a scrap of block refreshed performance for me.

Because it’s sold singly, longevity matters. Compared to a carbide-tooth recip blade on cast iron, I saw longer useful life and a more uniform cut rate. Compared to an angle grinder’s diamond wheel, life is in the same ballpark for similar footage, but you get the reciprocating saw’s control and reach advantages.

Heat, dust, and noise

• Heat: Keep orbital off, moderate the SPM, and avoid leaning in. The blade runs cooler and cuts faster when you don’t force it.
• Dust: Much less spark and plume than a grinder, but still wear a respirator—especially on CMU. A helper on a vac at the cut line makes a big difference.
• Noise: Noticeably quieter than a grinder. That matters indoors.

I don’t recommend wetting the cut with a reciprocating saw. Water and electricity don’t mix, and the debris management of this blade is good enough dry with vacuum assistance.

Where this blade fits in the kit

This isn’t a general-purpose metal blade. It’s a specialist that handles the ugly, abrasive jobs cleanly:
- Replacing sections of cast iron soil pipe in tight basements and crawlspaces
- Trimming cast-iron tubs or radiators where grinder sparks are a problem
- Adjusting block openings near combustible framing or finished areas
- Making controlled flush cuts where a grinder can’t physically fit

If you already own a chain-style soil pipe cutter and have room to use it, that tool is typically faster and dust-free for straight pipe cuts. But real-world constraints often rule that out, and this blade is the next best thing with less mess and risk than a grinder.

Limitations

• Not for general steel or stainless: A carbide-tooth metal blade will be faster on mild steel and EMT.
• Thick reinforced concrete is beyond its lane: the blade will cut block and cast iron, but aggregate and rebar in poured concrete can stall progress.
• Cost per blade is higher than bi-metal; it pays off only if you’re actually cutting abrasive materials.

Tips for best results

• Turn orbital action off and use moderate speed.
• Start with a light scoring pass to establish a track.
• Support the work to prevent pinching the blade—strap pipe, prop tub sections, or wedge block.
• Let the abrasive do the work. Too much pressure slows the cut and glazes the edge.
• Keep a vacuum at the cut line and wear eye/respiratory protection.
• If performance fades, make a few light passes in CMU to expose fresh diamond.

Value

Buying as a single blade makes sense if you’re approaching a one-off repair or a small batch of cuts. You’ll likely finish the task on a single edge, and the control and reduced spark/dust profile can save time on setup and cleanup. For trade users doing frequent cast iron or CMU adjustments, keeping one or two of these on hand rounds out the cutting kit—grinders for speed, reciprocating diamond for access and control.

Recommendation

I recommend this Bosch diamond-grit blade for anyone who needs a controllable, low-spark option for cutting cast iron and making small adjustments in concrete block. It trades some speed for precision and safety in tight spaces, and the 50-grit edge holds up well on the materials it’s designed for. If your work is mostly mild steel or you have ample room to use a chain cutter or grinder, you may not reach for it often. But for renovation scenarios where access, control, and reduced mess matter, it’s a reliable, confidence-building choice that earns its spot in the case.