Keyless locking assemblies (shrink discs) are essential for high-torque shaft-to-hub connections in modern industrial machinery. Unlike traditional keyways, they provide zero backlash, no shaft weakening, overload protection, and easy installation – making them the preferred choice for demanding applications.

The MLAT/AL-F series from Apex Coupling offers a double taper short-type keyless locking assembly with exceptional torque capacity up to 6400 N·m. This guide explains how keyless locking assemblies work, their key advantages, and how to select the right model for your application.

1. What Is a Keyless Locking Assembly (Shrink Disc)?

A keyless locking assembly (also called a shrink disc) is a friction-based mechanical device that connects a hub to a shaft without using keys or keyways. It consists of tapered inner and outer rings with high-strength clamping screws. When tightened, the rings are forced together, creating high radial pressure that locks the hub securely onto the shaft.

Key characteristics include:

• Zero backlash – No rotational clearance

• Keyless connection – No keyways, no shaft weakening

• Overload protection – Slips to protect equipment

• Reusable – Multiple installation cycles

• Easy installation & removal – No special tools required

2. MLAT/AL-F Series – Double Taper Short-Type Design

The MLAT/AL-F series features a double taper short-type design that offers several advantages:

✅ The double taper short-type design provides higher torque capacity in a shorter axial length compared to standard designs – making it ideal for space-constrained applications.

3. Shrink Disc vs Keyway – Quick Comparison

4. Why Keyless Locking Outperforms Keyways

Reason 1: Zero Backlash
The shrink disc 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 shrink disc applies uniform radial pressure around the entire circumference – no shaft weakening.

Reason 3: Overload Protection
Under extreme overload, the shrink disc 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 positioned and locked at any point or angle on the shaft – ideal for precise positioning.

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

Reason 7: Sealing Function
The contact surfaces of the shrink disc seal against corrosion and contamination – protecting the shaft-hub connection.

5. Direct Misumi MLAT Replacement

The MLAT/AL-F series is fully interchangeable with Misumi MLAT series:

• Same dimensions – drop-in replacement

• Same performance – meets or exceeds OEM specifications

• Better value – factory-direct pricing

✅ Upgrade without design changes – direct replacement for Misumi MLAT keyless bushings.

6. Applications Where Shrink Discs Excel

7. Real‑World Example – CNC Machine Upgrade

A CNC machine manufacturer was experiencing positioning errors and shaft damage due to keyway stress concentrations on their high-speed spindles. The keyways were causing backlash and requiring frequent shaft replacement.

They switched to Apex Coupling MLAT shrink discs (S45C, double taper, zero backlash). Results:

• Positioning accuracy improved – backlash eliminated

• Shaft damage eliminated – no keyway stress concentrations

• Installation simplified – no keyway fitting required

• Maintenance reduced – reusable design

• Cost savings – no more keyway machining

8. Installation & Maintenance Tips

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

2. Pre-center the assembly – MLAT/AL-F is not self-centering

3. Slide shrink disc into position – Position at desired axial location

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

5. Check concentricity – Verify alignment after tightening

6. For removal – Use the pre-drilled removal thread holes – no pullers required

7. Reusable – Can be reinstalled multiple times

💡 Important: Always use a torque wrench to ensure screws are tightened to the specified torque – under-tightening reduces torque capacity, over-tightening can damage the assembly.

9. Selection Checklist

• Series: MLAT or AL-F – double taper short-type high torque

• Material: S45C forged steel – high strength and durability

• Finish: Standard, black oxide, electroless nickel, zinc, or phosphating

• Bore: 30–65mm – match your shaft diameter

• Torque: Up to 6400 N·m – select based on your requirement

• Axial load: Up to 197 kN – select based on your requirement

• Overload protection: Yes – slips to protect equipment

• Reusability: Yes – multiple installation cycles

• Misumi MLAT replacement: Direct drop-in replacement

• Application: CNC, heavy machinery, packaging, textile, printing, wind power, automation

10. Conclusion

The MLAT/AL-F high torque shrink disc from Apex Coupling offers superior performance compared to traditional keyways – with zero backlash, no shaft weakening, overload protection, easy installation, reusability, and direct Misumi MLAT interchangeability. With S45C forged steel construction, double taper short-type design, 6400 N·m torque capacity, and multiple finish options, it is the ideal solution for CNC machine tools, heavy machinery, packaging equipment, and demanding industrial applications.

👉 Need a keyless locking assembly for your application? Contact us with your bore size, torque, and application requirements.