A jaw crusher is a machine that breaks large rocks, ore, or other hard materials into smaller pieces by squeezing them between two heavy metal plates. One plate stays fixed while the other swings back and forth, compressing material in the narrowing gap between them until it fractures and drops through. It’s one of the oldest and most widely used types of crushing equipment, typically serving as the first stage of size reduction in mining, construction, and recycling operations.
How a Jaw Crusher Works
The core mechanism is simple: pressure crushing. Material is fed into a wedge-shaped opening at the top of the machine, where it lands between a fixed jaw plate and a moving jaw plate. The moving jaw swings toward the fixed jaw in an elliptical motion driven by a rotating eccentric shaft, compressing whatever sits between them. When the moving jaw pulls back, broken fragments drop lower into the narrowing gap. This cycle repeats until pieces are small enough to fall out the bottom.
The output size depends on the gap at the bottom of the crushing chamber. Two settings control this. The closed side setting (CSS) is the smallest distance between the jaws during each cycle, while the open side setting (OSS) is the widest. The maximum size of any piece leaving the crusher is determined by the open side setting. Operators adjust these settings to control how fine or coarse the output will be.
A typical jaw crusher achieves a reduction ratio of about 6:1, meaning it reduces feed material to roughly one-sixth of its original size in a single pass. So a boulder entering at 600 mm would come out at around 100 mm or smaller.
Single Toggle vs. Double Toggle
There are two main mechanical designs, and the difference comes down to how the moving jaw gets its motion.
A single toggle jaw crusher has one eccentric shaft mounted at the top. The shaft’s rotation, combined with a single toggle plate, drives the moving jaw in a chewing motion that compresses material at both the intake and the discharge end of the chamber. This gives single toggle designs better throughput capacity for their size, which is why they dominate in modern quarrying and mining operations.
A double toggle crusher uses two shafts and two toggle plates. One shaft pivots at the top of the crusher while the other is an eccentric shaft that drives both toggle plates. This design produces a purely compressive motion with less of a rubbing action on the jaw plates. Double toggle crushers are better suited for extremely hard, abrasive materials because the jaw plates wear more evenly, but they process material more slowly than a single toggle crusher of comparable size.
Pivot Point Variations
Beyond the toggle distinction, jaw crushers are also classified by where the moving jaw pivots:
- Blake crusher: The swing jaw is fixed at the upper position, meaning the widest motion happens at the discharge end. This is the most common design for large-scale primary crushing.
- Dodge crusher: The swing jaw is fixed at the lower position, so the greatest movement occurs at the feed opening. This produces a more uniform output size but handles lower volumes.
- Universal crusher: The pivot point sits at an intermediate position, splitting the difference between the other two designs.
What Materials Jaw Crushers Handle
Jaw crushers are built for hard, tough materials. They’re commonly used to crush granite, basalt, limestone, quartz, and concrete. They also handle coal, various metal ores, and construction demolition waste. The general rule is that a jaw crusher works well on materials with a compressive strength below 320 MPa, which covers the vast majority of natural rock types and recycled construction materials.
The jaw plates themselves are often corrugated rather than smooth, especially when crushing hard, abrasive ores. The corrugation helps grip the material and improves fracture efficiency. Jaw crushers can also handle sticky feeds that might clog other types of crushers, making them a reliable first-stage option in varied conditions.
Industries that rely on jaw crushers include mining, cement manufacturing, road and railway construction, water infrastructure, chemical processing, and aggregate production. In nearly all of these, the jaw crusher serves as the primary crusher, taking raw blasted rock or large chunks and reducing them to a size that secondary crushers or screens can handle.
Key Parts and Wear Components
The main structural components of a jaw crusher include the frame (a heavy casting or welded steel body), the fixed jaw plate, the moving jaw mounted on a pitman (the swinging arm), the eccentric shaft, toggle plates, and flywheels that store rotational energy to smooth out the crushing cycle.
The jaw plates and cheek plates (side liners inside the crushing chamber) are the primary wear parts. They take the direct impact of every piece of material that passes through. For primary crushing of hard rock, these plates are typically made from Hadfield manganese steel containing 14 to 18 percent manganese. This material is exceptionally tough and work-hardens under impact, meaning it actually gets harder on the surface as it’s used.
For less demanding applications like secondary crushing or softer materials, operators may use alloyed steels or chrome-enhanced liners that balance wear resistance with cost. Some operations use rubber-backed liners in low-abrasion settings to reduce noise. Protection plates sit between the jaw dies and the crusher frame to shield structural surfaces from wear, particularly when processing very hard or tough material.
Liner quality has a direct impact on operating costs. Cheaper liners wear faster, leading to more frequent replacements and more downtime. Premium alloy liners cost more upfront but often last significantly longer, reducing the total cost per ton of material processed.
How Output Size Is Controlled
Operators control product size primarily by adjusting the closed side setting. A smaller CSS produces finer output but reduces throughput and increases wear on the jaw plates. A larger CSS lets more material through faster but produces coarser fragments.
The “throw” of the crusher, which is the difference between the open and closed side settings, also matters. A longer throw means the moving jaw travels farther with each cycle, which increases capacity but also increases the forces on the machine. The gape, or the distance between the jaws at the feed opening, determines the maximum size of material the crusher can accept. Feeding material that’s too large for the gape causes blockages and can damage the machine.
Because jaw crushers produce a range of particle sizes in a single pass rather than a perfectly uniform output, the crushed material typically goes to a vibrating screen afterward. Oversized pieces get recirculated back through the crusher, while correctly sized material moves on to the next processing stage.