Removing a Seized Blade Center Pin from a TD20G Dozer

[MikePhua]

Understanding the Blade Center Pin Assembly
On crawler dozers like the International TD20G, the blade center pin plays a critical role in connecting the blade to the C-frame, allowing tilt and angle adjustments. When switching between blade types—such as a piling blade and a tilt blade—the center pin must be removed and reinstalled. However, due to wear, misalignment, or deformation, the pin can become seized, making extraction a serious challenge.
Terminology Note

• Center Pin: A cylindrical steel shaft that secures the blade to the C-frame, allowing pivoting.
  
• C-Frame: The structural arm that supports the blade and connects it to the dozer chassis.
  
• Swaged: A condition where metal has been deformed under pressure, expanding and locking in place.
  
• Exothermic Torch: A high-temperature cutting tool that uses oxygen and a consumable electrode to burn through metal.
  

Common Causes of Pin Seizure

• Misaligned Bores: If the upper bore is worn or egg-shaped, the pin may bend during operation, locking it in place.
  
• Improper Fitment: A stepped pin machined to accommodate wear may bind if the bore geometry shifts under load.
  
• Burred Edges: Damage from previous blade configurations can leave sharp edges that cut into the pin.
  
• Corrosion and Debris: Rust and compacted dirt can create friction and prevent movement.
  
• Swaging from Force: Hydraulic or mechanical force applied during operation may deform the pin, especially if the blade frame is not properly aligned.
  

Mechanical Extraction Techniques
Several methods can be attempted before resorting to destructive removal:

• Hydraulic Jacking: Apply upward or downward force using a 30-ton bottle jack while manipulating the blade with the dozer or excavator.
  
• Slide Hammer Setup: Weld a nut or bolt to the top of the pin and use a slide hammer to apply repeated pulling force.
  
• Puller Assembly: Fabricate a puller using pipe, plate washers, and an impact wrench to draw the pin out gradually.
  
• Shock Loading: Maintain pressure on the pin while jiggling the blade through normal operation to break the bond.
  
• Heating and Cooling: Use a rosebud torch to heat the surrounding bore, then allow the pin to cool and contract for easier removal.
  

Destructive Removal Options
If mechanical methods fail, destructive techniques may be necessary:

• Drilling: Bore a pilot hole through the pin and enlarge it to reduce mass and allow contraction.
  
• Exothermic Torch: Use a lance to burn through the pin, especially effective if the pin is case-hardened.
  
• Air Arc Gouging: Suitable for cutting welds or flat surfaces, but less effective in deep bores due to pooling.
  
• Annealing: Heat the pin to reduce hardness before drilling or cutting.
  

In British Columbia, an operator fabricated a stepped pin from an 80mm excavator shaft. After months of use, the pin became immovable. Despite using a 30-ton jack and excavator force, the pin remained locked. Welding a bolt and rigging a puller setup allowed partial rotation, but full extraction was deferred due to time constraints.
Preventive Measures for Future Installations

• Recondition Bores: Machine or sleeve worn holes before installing a new pin.
  
• Use Anti-Seize Compound: Apply to the pin surface to reduce friction and corrosion.
  
• Avoid Over-Tightening: Excessive force during installation can deform the pin.
  
• Inspect Alignment: Ensure all bores are concentric and free of burrs.
  
• Log Pin Material and Hardness: Case-hardened pins may require special removal tools.
  

Conclusion
Removing a seized blade center pin from a TD20G dozer demands a combination of mechanical ingenuity and patience. Misalignment, wear, and deformation can lock the pin in place, requiring custom pullers, heat, and even destructive methods. With proper preparation and bore conditioning, future installations can avoid similar complications—ensuring smoother blade swaps and reduced downtime.