Why They Happen & How to Fix Them

You scheduled a jaw plate change for next month. But the plates gave out this week — again.

Jaw plates wear out faster than expected. They crack. They break. One side wears down while the other looks brand new. Output drops, but nobody can explain why.

Here’s the truth: most jaw plate failures are not caused by bad jaw plates.

They’re caused by the wrong material selection, wrong operation, or wrong feeding practices — and these are problems you can fix.

In this guide, we’ll cover:

• ✅ The top 7 jaw plate problemsoperators face
• ✅ The real reasonseach one happens
• ✅ Practical fixesyou can apply immediately

Let’s get into it.

Why Jaw Plate Selection Matters More Than You Think

Before we dive into the problems, it’s worth understanding what jaw plates actually do under load.

Manganese steel jaw plates work through a process called work hardening. When rock impacts the surface, when rock impacts the surface, the outer layer work-hardens progressively — while the core stays tough and impact-resistant. This balance between surface hardness and core toughness is what makes manganese steel the industry standard. (EvoQuip Wear Parts Guide)

But this only works when:

• The right manganese gradeis selected for the rock type
• The tooth profilematches the feed material and application
• Operating parameters(CSS, feed size, feed distribution) are correctly set

Get any of these wrong, and even the best jaw plates will fail early.

Problem 1: Jaw Plates Wear Out Too Fast

Short service life is the #1 complaint from jaw crusher operators worldwide.

Why It Happens

• Wrong alloy for hard rock.Standard 14% manganese steel simply isn’t hard enough for highly abrasive materials like granite, quartzite, or basalt. Granite and quartzite typically fall in the “Abrasive” to “Very Abrasive” range, with Abrasion Index values of 0.6–0.8+, which dramatically accelerates jaw plate wear. (Source: EvoQuip/Terex Crusher Wear Parts Reference Guide, 2018)
• Too many fines in the feed.Fine particles (below CSS size) act like grinding media inside the crushing chamber. Instead of being crushed, they grind against the jaw plate surface and accelerate abrasive wear.
• No pre-screening.Without a vibrating grizzly feeder or scalping screen, fines go directly into the crusher — the EvoQuip wear guide specifically recommends that screen aperture size should not exceed the crusher’s CSS setting to minimize this effect.
• CSS set too tight.A closed side setting that’s too small increases the contact time between rock and jaw plate, wearing both faster.

How to Fix It

Pro tip: Metso’s MX jaw plates can potentially double — and in some applications even triple — the wear life of standard manganese jaws, depending on rock type and operating conditions. (Source: Metso Nordberg C Series Jaw Crusher Wear Parts Application Guide, 2023)

Problem 2: Jaw Plates Crack, Break, or Chip

A jaw plate that shatters on the job is more than a cost problem — it’s a safety hazard.

Why It Happens

• Oversized feed entering the chamber.The maximum feed size for any jaw crusher should be approximately 80% of the feed opening — for example, a Sandvik CJ612 with a 1,200 × 1,100 mm opening has a maximum feed of 990 mm. For irregularly shaped material, the effective maximum feed size may be even lower — always consult your crusher’s instruction manual for the specific model. (Source: Sandvik CJ Series Technical Specification Sheet, Sandvik Mining and Rock Technology)
• Uncrushable material in the feed.Rebar, steel bolts, wire, and other tramp iron cause catastrophic jaw plate fractures. This is common in demolition recycling, quarries near old infrastructure, and cement plant processing.
• Wrong alloy — too brittle.High-chrome iron or counterfeit “high-manganese” jaw plates with insufficient manganese and no proper heat treatment are brittle. They do not work-harden — they fracture.
• No solution heat treatment (water toughening).Genuine manganese steel must undergo water toughening (solution annealing at ~1,050°C followed by water quench) to relieve internal stresses. Without it, the casting is brittle and prone to cracking. (ESCO Jaw Plate Alloy Guide)

How to Fix It

• Primary crushing always requires high-toughness jaw plates.For primary crushing, there’s really only one rule: always use high-toughness 18% Mn jaw plates. Impact resistance matters more than abrasion resistance at this stage.
• Install a magnetic separator (overbelt or drum-type)before the crusher to remove tramp iron. This single step prevents the majority of catastrophic jaw plate breaks.
• Verify your supplier’s material certification— request mill certificates showing manganese %, carbon %, and confirmation of water toughening process. (Source: ESCO Crusher Wear Parts and Accessories Catalog)
• Never use high-chrome or brittle white iron jaw plates in primary crushing stages.

Problem 3: Uneven Jaw Plate Wear

One side wears down twice as fast. The bottom wears out before the top. Sound familiar?

Why It Happens

• Off-center feeding.Material consistently hitting one side of the crushing chamber concentrates wear on that side. This is one of the most common — and most overlooked — causes of uneven jaw plate life.
• Excessive fines at the bottom.Fine material packs into the lower section of the chamber and grinds the bottom of the jaw plate without actually being crushed.
• Wrong tooth profile.Some tooth profiles trap material rather than allowing it to flow through, creating localized wear zones.
• Crusher not level.Even a few degrees of tilt changes how material distributes inside the chamber.
• Incorrect jaw-to-jaw clearance.If the gap between fixed and swing jaw is uneven across the width, one side always works harder.

How to Fix It

• Center your feed belt or chute.Feed material should enter the crushing chamber centrally and evenly. Install a deflector plate if your feed arrangement is off-axis.
• Switch to a coarse corrugated or wide-tooth profile(e.g., Sandvik Wide Teeth “WT” profile) — these profiles improve material flow and reduce bottom packing. (Source: Sandvik CJ Series Technical Specification Sheet, Sandvik Mining and Rock Technology)
• Don’t overlook the mechanical basics either:
  • Check crusher frame levelness with a precision level tool — correct any deviation.
  • Inspect jaw die installation: ensure both sides are properly seated and wedge-locked at equal torque.
• Rotate or flip jaw plateswhen top half shows less wear than bottom — this redistributes wear and extends total service life.

Problem 4: Jaw Plates Slip — Can’t Grip Material, Low Output

The crusher is running, rocks are bouncing around, but very little is actually getting crushed.

Why It Happens

• Smooth or slippery feed material.River pebbles, weathered limestone, and rounded gravel are notoriously difficult for jaw plates to grip. Flat tooth profiles have minimal bite angle on smooth surfaces.
• Teeth worn flat.Once jaw plate teeth wear below 90% of their original profile height, gripping ability drops significantly. (Source: EvoQuip/Terex Crusher Wear Parts Reference Guide, 2018) EvoQuip’s wear guide further states that a minimum 10 mm difference between tooth peak and valley must be maintained — below this, the plate must be replaced immediately. A simple go/no-go check: if you can’t feel a clear ridge-and-valley texture when running your gloved hand across the jaw face, it’s time to replace. (Source: EvoQuip/Terex Crusher Wear Parts Reference Guide, 2018) > Note: Specific wear thresholds may vary by crusher model — always refer to your OEM’s instruction manual for model-specific limits.
• Incorrect nip angle.For most single-toggle jaw crushers (e.g., Sandvik CJ series), the optimal nip angle is 16–23 degrees. Outside this range, material slips upward instead of being drawn down into the chamber. (Source: Sandvik CJ Series Technical Specification Sheet, Sandvik Mining and Rock Technology)
• Feed size too large for the opening.Oversized material rests on the jaw faces without being engaged properly.

How to Fix It

Note: Metso’s “Super Grip” jaw plate profile is specifically engineered for gravel and smooth natural rock, using aggressive tooth geometry to increase contact surface area and draw material down. (Source: Metso Nordberg C Series Jaw Crusher Wear Parts Application Guide, 2023)

Problem 5: Bottom Wear-Through — Root of Jaw Plate Wears First

The top of the jaw plate still looks fine, but there’s a hole at the bottom.

Why It Happens

• Too many fines in the feed.Without large rocks to force the fines through, fine particles sit at the bottom and are ground repeatedly instead of being discharged.
• Jaw plate bottom is too thin.Some standard jaw plates have insufficient wear metal at the lower section — this is a design limitation, not a material failure.
• Feed is all fines, no coarse fraction.Without larger rocks creating the impact-and-push cycle, fine material grinds the bottom continuously.

How to Fix It

• Use a Quarry Thick jaw plate(e.g., Metso Quarry Thick XT710) — the fixed jaw is 40 mm thicker than the standard Quarry profile, providing significantly more wear metal at the bottom. (Source: Metso Nordberg C Series Jaw Crusher Wear Parts Application Guide, 2023)
• Switch to a wide-tooth or coarse corrugated profileto improve fines passage — wider gullets (valleys between teeth) allow fine material to discharge faster instead of packing at the bottom.
• Add pre-screening Remove fines before they enter the crusher — a vibrating grizzly feeder is the most effective solution here.

Problem 6: Loose Jaw Plates — Knocking, Rattling, Vibration

A banging sound from the crushing chamber during operation is never a good sign.

Why It Happens

• Worn or damaged wedge blocks.Wedge blocks (lock wedges) are what hold jaw plates firmly against the jaw die seat. Once they wear or deform, the jaw plate can shift slightly during operation, creating impact and noise.
• Improper installation.Jaw plates that aren’t fully seated or aren’t installed with correct torque on fasteners will loosen under load.
• Wrong-size replacement jaw plates.Non-OEM or low-quality aftermarket jaw plates may have slightly different dimensions — even 1–2 mm difference in thickness causes improper seating.
• Fastener loosening over time.Bolts and wedges vibrate loose during normal operation if not checked regularly.

How to Fix It

• Inspect and replace worn wedge blocksat every jaw plate change — this is a low-cost part that prevents expensive jaw plate and crusher frame damage.
• Follow the OEM torque specification during installation. Use a calibrated torque wrench.
• Powerscreen’s own field testing shows that their HD jaw plates deliver over 30% longer wear lifecompared to their standard liner equivalent — a gap that widens further when non-OEM parts with incorrect dimensions are used. (Source: Powerscreen HD Fixed Jaw Plates Product Sheet)
• Implement a weekly bolt-check routineas part of preventive maintenance. Loose jaw plates can damage the jaw die seat and the main frame if left unaddressed.

Problem 7: Too Many Flaky or Slabby Products — Poor Shape

Your downstream process needs cubical product, but you’re getting flat slabs and elongated pieces.

Why It Happens

• Flat tooth profile produces flat product.A smooth or low-relief jaw plate surface applies force over a large area, which tends to compress and flatten rather than break material along natural fracture lines.
• Incorrect nip angle.An overly wide jaw angle reduces the amount of crushing action per stroke.
• Feed material is inherently flaky.Shale, slate, and some limestone formations naturally break into slabs — jaw plate design alone can’t fully compensate.

How to Fix It

• Switch to an Anti-Slab jaw plate(e.g., Metso Anti-Slab XT710 or ESCO Slab Breaker) — these feature non-uniform, alternating tooth heights that force material to rotate and break along multiple fracture planes, producing more cubical product. (Source: Metso Nordberg C Series Jaw Crusher Wear Parts Application Guide, 2023)
• Review nip angle: a tighter, more aggressive jaw angle creates more compressive force per stroke.
• For naturally flaky feed, consider adding a secondary impact crusherin the circuit — jaw crushers are compression machines and have inherent limitations with flat material.

Quick Reference: Jaw Plate Problem Diagnosis Chart

How to Choose the Right Jaw Plate for Your Application

Not sure which jaw plate type fits your site? Use this selection logic:

Step 1 — Know your rock:

• Hard, abrasive (granite, quartzite): 22% Mn or TiC composite
• Medium abrasion (limestone, basalt): 18% Mn standard or high-grade
• Soft, low-abrasion: 14% Mn (reduces cost, sufficient wear resistance)

Step 2 — Know your feed:

• Blasted rock with coarse fraction: Standard, Quarry, or Superteeth
• Smooth river gravel or rounded rock: Super Grip or Sharp Teeth
• Fines-heavy feed: Wide Teeth (WT) or Coarse Corrugated
• Slabby or flat feed: Anti-Slab or Slab Breaker

Step 3 — Know your primary goal:

• Maximum life: Quarry Thick + 22% Mn
• Maximum toughness: 18% Mn high-impact
• Best product shape: Anti-Slab profile
• Maximum grip: Super Grip or Sharp Teeth

The Bottom Line

Most jaw plate problems can be avoided with three fundamentals:

Choose the right material for your rock type — manganese grade, alloy, and heat treatment all matter.

Use the right tooth profile for your feed — one profile does not fit all applications.

Control your feed and maintain correctly — even the best jaw plate will fail quickly with wrong feeding or improper maintenance.

The jaw plate is the #1 wear item on any jaw crusher. Getting it right means more uptime, lower cost per ton, and better product quality — whether you’re running a quarry, a mine, or a cement plant.

Jaw Plate Problems? Tell Us Three Things.

Our engineering team has worked with operations running Metso C series, Sandvik CJ, Powerscreen Premiertrak, and other major crusher models — across granite quarries, limestone mines, and cement plant applications.

Tell us three things:

• What rock you’re crushing(granite, limestone, river gravel, slag, etc.)
• Which crusher you’re running(brand + model if possible)
• What’s going wrong(fast wear, cracking, uneven wear, low output, etc.)

That’s all we need. We’ll respond with a specific recommendation within 24 hours — at no cost, no obligation.

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Data references: Metso Nordberg C Series Wear Parts Guide; Sandvik CJ Series Technical Documentation; ESCO Jaw Plate Alloy & Selection Guide; EvoQuip/Terex Wear Parts Reference Guide; Powerscreen HD Fixed Jaw Liner Technical Sheet.