
Common Causes of Failure
Striking Bars
Chipped rod end; damaged coupling
Off-line drilling
Too much rotation when pulling rods out of hole
Worn chuck; heavy rotation loads
Worn chuck-driver bushing
Sever overfeeding
Fatigue from water seal recess
Couplings
Scalding/bluing
Improper chamfering of drill steel
Steels not seating together in coupling
Operating machine with coupling
Touching centralizer
Off-line drilling
Drilling with rod not firmly screwed into coupling.
“off-line drilling”
Section 3
Page 3-12
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