Welding Worn Shanks

[MikePhua]

Overview of Shanks and Significance
In the context of heavy earth‑moving equipment, a shank refers to the protruding steel component on a bucket, ripper or blade attachment that holds a tooth or tip and transmits load forces into the tooth. Over time, the shank face and retainer area suffer wear from abrasion, impact and metal fatigue. When the shank becomes excessively worn, the tooth retention system (pins, clips, bolts) fails or the shank fails structurally, the question often arises: should one repair the shank by welding and rebuilding, or simply replace it ?
Causes of Shank Wear and Damage
Shank wear typically arises from a combination of:

• Abrasive soil and rock contact grinding against the shank face and retainer pocket.
  
• Impact loading when the tooth strikes rock or root stumps, inducing micro‑fractures or fatigue.
  
• Looseness of the tooth‑to‑shank fit causing movement and accelerated wear at the interface.
  
• Retainer pin failure due to bending stress, corrosion or repeated impact cycling.
  
• Neglected maintenance allowing the shank to wear back to the retainer hole or bore, compromising strength.
  

One anecdote: an operator of a 22‑ton excavator found that after 5000 hrs the shank on one bucket had worn to the point the tooth “rattled” in the holder, and once a retainer pin sheared while working a granite outcrop — the bucket tooth popped off mid‑job, causing downtime and loss of production.
When Welding Rebuild Makes Sense
Repair by welding or hardfacing can be worthwhile in cases where:

• The shank is not structurally cracked or broken and still retains ~70 % of its original material cross‑section.
  
• Replacement shanks are very high cost or lead‑time is long.
  
• The machine value and bucket usage justify investment in repair versus replacement.
  
• Skilled welder and proper procedures are available on‑site.
  

For example: on a dozer ripper shank serving in light ripping duty the cost of a new shank may run thousands of dollars; a rebuild by welding may cost a few hundred and provide acceptable life extension.
When Replacement is Better
Replacement is recommended when:

• Wear has reached or passed the retainer‐hole, bore or pin seating area to more than ~30 % section loss.
  
• The shank has cracked or fractured through the web or base.
  
• Tooth retention geometry is compromised such that weld rebuild cannot restore dimensional tolerances.
  
• The repair cost approaches or exceeds the replacement cost (considering labour, downtime, fit‑up).
  
• The machine is critical to high‑production operations where unplanned repair downtime is not acceptable.
  

One report found that on an excavator bucket the labour to arc‑air cut and weld new shank was about 4‑6 hours; when parts cost were similar to labour, replacement was often the better choice.
Welding and Hardfacing Techniques
Key steps and considerations in the welding rebuild process:

• Pre‑heating: For steel of 20–40 mm thickness, pre‑heat to ~150‑200 °C to avoid cracking.
  
• Scarfing and preparation: Remove worn or cracked material, clean the base metal, bevel edges for good weld penetration. An oxy/acetylene “scarfing tip” or air‑carbon‑arc removal may be used.
  
• Electrode/wire selection: Standard 7018 low‑hydrogen rod or equivalent is often used for build‑up. Hardfacing rods can be used for extreme wear zones, but caution: excessive hardface may result in brittleness and tooth break‑off.
  
• Build‑up layers: Deposit weld metal in layers, allow inter‑pass cooling, grind flats and shoulders to restore fit for tooth or tip.
  
• Heat treatment / slow cooling: After weld, wrap the piece in a weld blanket or inhibitor to cool slowly over several hours; in thick sections this prevents residual stress and cracking.
  
• Dimensional control: After build‑up, machine or grind to correct profile and ensure fit‑up of tooth and retainer pin/bore. Check that the tooth still fits snugly and that retainer pin alignment is maintained.
  
• Post‑repair inspection: Once welded, inspect for cracks with dye‑penetrant or magnetic particle, and test under load if possible before full production use.
  

Recommendations and Best Practices
Here are suggestions to maximize success when rebuilding shanks:

• Document original dimensions of shank face, pin bore and tooth fit‑seat before wear occurs; this facilitates accurate rebuild.
  
• Specify weld build‑up to restore original geometry (±1 mm where feasible) so that new or re‑used teeth fit properly.
  
• Consider switching to hardened or wear‑resistant steel teeth if operating in highly abrasive conditions; this reduces wear on the shank face.
  
• Maintain proper fit tolerances between shank and tooth; any looseness causes shock loading on welds or pins.
  
• Monitor rebuilds after 50–100 hours of high‑impact duty and again at 250–500 hours to catch early defects.
  

Case Story and Industry Outcome
In one example, a medium‑sized contractor refurbished a fleet of six excavator buckets by rebuilding worn shanks via hardfacing instead of ordering new components. The contractor estimated a cost of about 30 % of new shanks and achieved about 80 % of original service‑life before the next major overhaul was required. The trade‑off: increased inspection frequency and stricter weld control, but considerable savings and reduced downtime. A local dealer quoted a buy‑one‑get‑one‑free deal on shank/tooth sets which prompted some operators to replace outright; that’s a reminder that cost‑benefit must be evaluated at the time of decision.
Summary
Rebuilding worn shanks by welding and hardfacing is a viable maintenance strategy in many earth‑moving applications—provided the wear is manageable, the repair is executed with proper metallurgical and welding procedures, and the economics favour repair over replacement. Understanding when to weld and when to replace is critical to maintain productivity, safety and equipment life.