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Reciprocating saw blades are consumables, but on metal they shouldn’t be single-use. If you’re burning through a fresh blade every few cuts in steel, conduit, or angle iron, it’s not just the blade — it’s speed, pressure, tooth count, and heat management. Fix those and a $3 bimetal blade will outlast a whole pack used poorly.
Why Metal Kills Blades Fast
On wood, a recip blade fails by dulling slowly. On metal, it fails catastrophically. The three main failure modes are tooth stripping, heat softening, and fatigue cracking.
Tooth stripping is the most common. It happens when too few teeth are in contact with the work. The blade grabs, a tooth bends or breaks, and the next tooth takes even more load until the whole edge is wiped. Heat softening is second. Metal-on-metal friction can push the cutting edge past 600°F in seconds, especially with stainless or hardened steel. Bimetal teeth lose hardness and then round over immediately. You’ll see straw or blue discoloration on the blade as a tell. Fatigue cracking is what snaps blades at the shank or in the middle — too much bending, too much orbital action, or a blade that’s too long and flexes.
If your blades are coming out with missing or flattened teeth in one section, it’s stripping. If the teeth look smooth and rounded and the blade is discolored, it’s heat. If the blade bends and breaks, it’s technique or length.
Match the Blade to the Metal
Tooth count (TPI) is more important than brand. The rule is simple: at least 3 teeth should be in contact with the material thickness at all times. Fewer than that and teeth straddle the edge and rip off.
For thin sheet metal, auto body panels, or EMT conduit under 1/16″ wall, you want 18-24 TPI. For 1/8″ to 1/4″ mild steel like angle iron, strut, or flat bar, 14-18 TPI is the sweet spot. For thick steel over 1/4″, pipe with wall thickness over 3/16″, or demolition where you hit wood with nails, 10-14 TPI cuts faster without clogging.
Material matters just as much. Don’t overthink it for mild steel, but pick based on what you’re cutting most:
| Blade Type | Best For | Life on Mild Steel | Cost Trade-off |
|---|---|---|---|
| Bi-Metal (HSS teeth on spring steel back) | Mild steel, angle iron, conduit, nail-embedded wood, general demolition | Baseline (1x) – 10-30 cuts in 1/8″ steel per blade with good technique | $2-$4 per blade. Best value for most users. |
| Bi-Metal with Cobalt (M42) | Harder steels, stainless exhaust, hardened bolts | 1.5x to 2x longer than standard bi-metal on hard metals | $4-$7 per blade. Worth it for stainless or frequent metal work. |
| Carbide-Tipped / Carbide Grit | Cast iron, stainless, high-strength steel, prolonged production cuts | 5x to 10x longer than bi-metal, especially in abrasive metals | $9-$15 per blade. Expensive upfront, cheapest per cut if you do a lot of metal. |
| Diamond Grit | Cast iron, tile, fiberglass – not for steel | Poor on steel, teeth don’t cut it | Don’t buy for metal jobs. |
For 90% of DIY and maintenance work in mild steel, a standard bimetal reciprocating saw blades 14 TPI pack is all you need. Step up to cobalt or carbide only when you’re cutting stainless, cast iron, or doing 20+ metal cuts a day. A 6-inch blade will run cooler and break less than a 9-inch or 12-inch on thin metal. Use the shortest blade that will get through the material plus 1/2″ clearance.
Speed, Pressure, and Stroke Settings
This is where most blades die early. A reciprocating saw is not a wood saw when it’s on metal — you have to slow down.
First, turn off orbital action. Orbital mode swings the blade in an ellipse to clear wood chips faster. On metal it just hammers the teeth, increases vibration, and causes bouncing that strips teeth. Use straight, 0-orbit reciprocation for all metal.
Second, run at low to medium speed, not full trigger. For steel, 40-60% of max strokes per minute is ideal. On a variable-speed saw that’s roughly speed setting 2-3 out of 5, or about 1,500-2,000 SPM on a saw that tops out at 3,000 SPM. Let the teeth cut. If you see sparks showering and hear a high-pitched scream, you’re too fast and too hot.
Third, ease up on pressure. You should not be leaning your body weight into the saw. Apply 5-10 lbs of steady forward force and let the shoe stay firmly planted against the work. The saw’s weight plus light pressure is enough. Heavy pressure bends the blade, stalls the teeth, and creates heat instead of chips. Good cutting makes small, distinct curled chips. Dust or blue-black powder means you’re rubbing, not cutting.
If your saw has a pendulum or adjustable shoe, extend the shoe so only 1/4″ to 3/8″ of blade is exposed past the material on the backstroke. Less overhang means less flex and longer life.
Heat Is the Real Killer
Heat dulls a blade permanently. Once the edge is blued, it’s done — no amount of cooling will re-harden it. Prevention is the only option.
For any cut longer than 15-20 seconds in steel, use lubrication. A few drops of cutting oil for metal drilling and sawing applied directly to the cut line drops friction and temperature by a third. Paste wax or even WD-40 is better than nothing for thin sheet metal, but sulfur-based cutting oil is best for thick steel and stainless. Apply before you start and again every 30 seconds on long cuts. You want the chips to look wet, not dry.
Don’t use water. It cools but doesn’t lubricate and it will rust the workpiece and your blade.
Take breaks on long cuts. On 1/4″ plate or 2″ solid round, cut for 20-30 seconds, back off for 10 seconds while the blade spins in air to shed heat, then re-enter. The blade should never be too hot to touch for a second near the shank. If it is, you are cutting too fast or with too much pressure.
Clamping also helps with heat. Vibration creates friction. If the metal can flex or rattle, the blade rubs. Clamp within 2-3 inches of the cut on both sides if possible, and sandwich thin sheet metal between plywood scraps to dampen it.
Technique That Saves Teeth
A few habits add 2x to 3x life regardless of blade price.
Start the cut correctly. Don’t plunge the tip into the metal. Tilt the saw so the shoe is anchored and the blade just kisses the edge at a shallow angle, start slowly, and then rock upright once a kerf is established. This prevents the initial grab that snaps teeth.
Keep the shoe tight. The shoe is not optional on metal. It should be pressed firmly against the work the entire cut. It reduces vibration, keeps the blade from bending, and gives you control. If you are cutting freehand with the blade flexing in mid-air, expect short life and a bent blade.
Avoid twisting. Let the blade cut straight. If you need a curve in sheet metal, make relief cuts instead of forcing the blade to turn while under load.
Replace before total failure. A blade that is starting to cut slowly is generating more heat. Swap it and save it for rough demolition work. Pushing a dull blade on metal just overheats your saw and work-hardens the steel, making the next blade’s job harder.
For heavy users, carbide reciprocating saw blades for metal are worth stocking for the nasty jobs — cast iron soil pipe, stainless, or hardened all-thread — where bimetal dies in one cut. Don’t use them for everything, though. Their carbide teeth are brittle; they will chip if you bend or twist them, and at $12 a blade, that’s an expensive mistake. Use bimetal for general steel and save carbide for when bimetal fails too fast.
When to Stop Trying to Save the Blade
A reciprocating saw is a demolition tool, not a precision metal saw. If you are making more than 10 clean cuts in 1/8″ or thicker steel in a day, a reciprocating saw is the wrong tool and no blade will fix it. A portable bandsaw will cut faster, straighter, and a $15 bandsaw blade will last for hundreds of cuts. An angle grinder with a thin cutoff wheel is faster for flush cuts and rebar.
Use the recip for what it does best: awkward positions, overhead cuts, pipe in place, and demolition where you need reach. For bench work, clamp the metal and use the bandsaw. You’ll spend less on blades in a month than you will in a week forcing the recip to do it all.