What is the main shaft assy?

It is the single component that holds your cone crusher together—literally. The Main Shaft Assembly is the structural core of your crusher. It supports the mantle, drives the crushing motion, and absorbs the immense forces generated when breaking rock. Without it, your crusher is nothing more than a steel shell. While mantle and bowl liner handle the daily wear, the main shaft assembly determines whether your machine runs reliably for years or becomes a recurring source of unplanned downtime. It is the difference between a crusher that delivers consistent production and one that keeps your maintenance team busy. In this article, we’ll walk you through what the main shaft assembly is, its key components, and the manufacturing standards that ensure it performs as reliably as—or better than—any original equipment.

What Is the Main Shaft Assy?

The main shaft assembly is the central load-bearing and motion-transmitting component in a cone crusher. It serves two critical functions:

• Structural support: Carries the mantle and transmits crushing forces into the crusher frame
• Motion generation: Delivers the gyratory movement that creates the crushing action

Designed for a service life measured in years—not hours—the main shaft operates under extreme conditions: high cyclic loads exceeding several hundred tons, shock loading from tramp material, and continuous exposure to dust, vibration, and temperature fluctuations.A main shaft assembly is not a single piece. It is a precision assembly of multiple components that must work together with exacting tolerances. Any deviation in geometry, material integrity, or assembly procedure directly affects crushing efficiency and operational uptime.

Key Components of a Main Shaft Assembly

• HEAD: The main body that supports the mantle. Mounts to the main shaft via precision taper fit, providing the foundation for the crushing surface.
• MAIN SHAFT: The central structural member. Transmits eccentric motion to the head and supports all crushing loads. Forged from high-strength alloy steel with precision-ground bearing surfaces.
• PROTECTION BUSHING: Fits over the main shaft to provide the bearing interface between the shaft and eccentric bushing. Prevents direct metal-to-metal contact and maintains proper oil film clearance.
• SEAL: Prevents dust, water, and contaminants from entering the bearing surfaces and lubrication system. Essential for maintaining oil cleanliness and component life.
• LOCK WASHER: Prevents loosening of threaded connections under vibration. Provides a consistent clamping force and must be replaced after each disassembly.
• HEXAGON SOCKET HEAD CAP SCREW: Secures critical components such as the protection bushing and locking mechanisms. Requires precise torque application to withstand cyclic loading.

What are the parts included in the main shaft assy?

Eg: GP200 ONA-MM0310111

Materials and Manufacturing Process

We supply main shaft assemblies forged from high-strength alloy steel—the same material grade used in original equipment. Each unit is 100% dynamically balanced, ensuring smooth operation and minimizing vibration-related wear. Every assembly is shipped complete with main shaft, protection sleeve, key, seals, and mounting bolts, accompanied by full material and dimensional inspection reports. Backed by a 1-year warranty, our main shaft assemblies are built for reliable performance in the harshest operating conditions.

Why Choose Our Main Shaft Assemblies?

As a factory-based manufacturer, we deliver high-quality components at competitive prices by eliminating unnecessary markups. Our fast global delivery ensures you get the parts you need when you need them—minimizing costly downtime. With stocked inventory for popular models and custom orders available on short lead times, we offer flexibility that larger suppliers often cannot match. Every order is supported by direct communication with our engineering team, ensuring you get the right component for your specific application.

Our Available Main Shaft Assemblies

We manufacture main shaft assemblies to match original equipment specifications, ensuring seamless interchangeability with Metso and Sandvik cone crushers. 

The following is a list of the main shaft assemblies suitable for Metso and Sandvik cone crushers:

Reliability You Can Count On

The main shaft assembly is the foundation of your cone crusher—a precision assembly that must withstand millions of load cycles over its service life. As a factory-based manufacturer, we combine traceable materials, rigorous quality control, and precision machining to deliver components that perform reliably in the harshest operating conditions.

All names, marks, models, symbols and descriptions are used for reference purposes only and it is not impied that any of the parts/brands listed are the product of any company other than ONA. We are not agents or distributors for any of the above mentioned brands nor do we have any commercial relationship or association with them.