Xuanwa Group
Blog
25
2026
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08
Bullet Teeth Wear Analysis: When to Replace Rotary Digging Teeth
Author：
The Hidden Cost of Waiting Too Long
Every piling contractor knows teeth wear out. What most underestimate is the compounding cost of running worn teeth: slower penetration, higher fuel burn per meter, extra torque load on the rig, and heat damage to tooth holders. A worn tooth doesn't just stop cutting — it makes the whole drilling system pay for it.
Field data from GCC projects shows penetration rates dropping 30–40% when carbide tips lose more than half their protrusion. On a 500-pile job, that is days of rig time.
Read the Wear Pattern
Uniform flank wear — normal life
Even wear across the carbide tip and body means the tooth matched the formation and ran at correct rotation speed. Replace when the carbide protrusion is roughly 8–10 mm or less, or when the tip radius has rounded off noticeably.
One-sided wear — rotation failure
If teeth wear on one flank only, the tooth is not rotating in its holder. Causes: seized holders packed with clay, worn holder sleeves, or a broken tooth pin. Fix the holder, not just the tooth — otherwise every new tooth wears the same way within days.
Carbide tip loss / spalling — formation mismatch
Whole or partial carbide loss means the tooth is taking impacts it was never designed for: boulders, hard limestone bands, or unblasted rock. Switching to a tougher grade (like our 42CrMo body + YG8 carbide rotary digging teeth) or moving to a core barrel for that interval is usually cheaper than replacing spalled teeth every shift.
Body erosion behind the tip — abrasive sand
When the steel body behind the carbide wears away faster than the tip itself, the tooth "loses support" and the carbide snaps off. This is the classic Gulf coastal sand signature. Rotation management and harder-facing on the body extend life.
Holder pocket wear — the silent killer
Check the holder seats at every tooth change. An oval, loose pocket lets the tooth wobble, which cracks carbide and accelerates everything above. Holders are cheap relative to the teeth they protect — replace on schedule, not on failure.
Setting the Right Replacement Interval
Use meterage, not calendar days:
Formation Type | Typical Tooth Life (per set) | Inspection Interval |
Loose–medium sand | 400–800 m of drilling | Daily |
Dense sand / gravel | 150–400 m | Every shift |
Weathered limestone | 60–150 m | Every 4–6 piles |
Rock / core barrel work | 40–100 m | Every pile |
(Ranges assume standard bullet teeth on a 20–30 tonne class rotary rig; adjust for rig torque and formation UCS.)
The economic rule: replace a tooth when the cost of lost penetration per hour exceeds the cost of the tooth per hour. In practice, most GCC contractors land on replacing at every shift-end inspection for rock work, and every 2–3 days in sand.
Stock Strategy for GCC Contractors
Because wear intervals swing with formation, the worst position is having rigs idle waiting for teeth. Our Abu Dhabi KIZAD warehouse keeps rotary digging teeth in stock for same-day collection or dispatch — covering XCMG, Sany, Zoomlion and Bauer tool configurations.
Free Wear Audit
Send us photos of your worn teeth (a phone shot of the tip, flank and holder is enough) and our engineers will tell you what the pattern means and what to change — formation, grade, or holder. Get in touch.
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