For decades, keyways have been the standard method for connecting shafts and hubs. But keyless locking assemblies (shrink discs / power locks) offer significant advantages in torque capacity, precision, maintenance, and equipment protection.

The Z22 series from Apex Coupling is a high-precision keyless power lock assembly that eliminates the need for keyways while providing superior performance. This guide compares keyless locking assemblies with traditional keyways and explains why the Z22 is the smarter choice for modern industrial applications.

1. Quick Comparison: Keyless Locking Assembly vs Keyway

2. What Is a Keyless Locking Assembly?

A keyless locking assembly (also called a shrink disc, power lock, or clamping element) is a mechanical device that creates a friction-lock connection between a shaft and a hub. It consists of:

• Tapered inner and outer rings

• High-strength clamping screws (12.9 grade)

When the screws are tightened, the tapered rings are forced together, creating high radial pressure that locks the hub onto the shaft. No keys, keyways, or threads are required.

3. The Z22 Advantage – Why It Outperforms Keyways

Reason 1: Zero Backlash
The Z22 friction-lock connection has no rotational clearance – ensuring precise positioning for servo motors, CNC machines, and automation equipment.

Reason 2: No Shaft Weakening
Keyways create stress concentrations that reduce shaft strength. The Z22 applies uniform radial pressure around the entire circumference – no shaft weakening.

Reason 3: Overload Protection
Under extreme overload, the Z22 will slip, protecting connected equipment from damage – a feature impossible with keyways.

Reason 4: Easy Installation & Removal
No heating, cooling, or special tools – simply tighten screws to install, loosen screws to remove.

Reason 5: Adjustability
The hub can be adjusted axially and radially during installation – ideal for precise positioning.

Reason 6: Reusability
The Z22 can be disassembled and reinstalled multiple times without damage – reducing long-term costs.

4. 12.9 Grade Screws – The Key to Reliable Clamping

The Z22 series features 12.9 grade high-strength screws:

• High tensile strength – Withstands high clamping forces

• Superior fatigue resistance – Reliable under cyclic loads

• Precise torque control – Consistent clamping pressure

✅ 12.9 grade is the highest strength class for metric screws – ensuring maximum clamping force and reliability.

5. Material Options – 45# Steel vs GCr15 Bearing Steel

6. Surface Finishes – Black Oxide vs Nickel Plating

7. Applications Where Keyless Locking Excels

8. Real‑World Example – Conveyor Drive Upgrade

A manufacturing plant was experiencing frequent downtime due to keyway failure on conveyor drive shafts. The keyways would wear over time, causing backlash and misalignment.

They switched to Apex Coupling Z22 keyless locking assemblies (45# steel, 12.9 grade screws, black oxide finish). Results:

• Keyway failures eliminated – friction-lock connection

• Backlash eliminated – zero rotational clearance

• Maintenance reduced – easy installation and removal

• Equipment protected – overload slip prevented damage

• Cost savings – reusable design reduced spare parts

9. Installation & Maintenance Tips

1. Clean shaft and hub bore – Remove oil, grease, and debris

2. Check dimensions – Ensure shaft and bore are within tolerance

3. Apply light oil to screws – Ensures accurate torque application

4. Tighten screws evenly – Use a torque wrench in a star pattern

5. No lubrication on tapered surfaces – Dry for maximum friction

6. For removal – Loosen screws evenly – no pullers required

7. Reusable – Can be reinstalled multiple times

10. Selection Checklist

• Shaft diameter: 15–100 mm – select the correct Z22 model

• Torque requirement: Up to 5000 N·m – ensure it exceeds your application torque

• Material: 45# steel (standard) or GCr15 bearing steel (heavy-duty)

• Surface finish: Black oxide (standard) or nickel plating (corrosion resistance)

• Application: Manufacturing, packaging, textile, mining, CNC, automation

11. Conclusion

The Z22 keyless power lock assembly from Apex Coupling offers superior performance compared to traditional keyways – with zero backlash, no shaft weakening, overload protection, easy installation, and reusability. With 45# steel or GCr15 construction, 12.9 grade screws, and black oxide or nickel finishes, it is the ideal solution for manufacturing plants, farms, construction, mining, and general industrial power transmission.

👉 Need a keyless locking assembly for your application? Contact us with your shaft diameter, torque, and finish requirements.