TEI TE260, Service And Maintenance Manual

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Common Causes of Failure
Surface damage caused by
hammering or careless use of drill
steels
Corrosion originating in bore,
Accelerated by high stress conditions
Off-line drilling
Fatigue from surface irregularity,
Caused by excessive heat and
welding action between coupling
and steel
Button Bits
Outer gage wear:
Pinching of bit in hole.
Over rotation, reduce down feed re-
sharpen immediately
Fractured/Cracked button:
Improper sharpening
Skirt split/fracture:
Off-line drilling
Worn threads
(Often caused when finishing for bit)
(Check thread on steels and bits)
Flattened carbide top:
Normal wear, re-sharpen
immediately
Loose or lost button:
Loose chucking/rattling the string
Body deterioration:
Not enough air/water pressure
For proper flushing of bit face
Ring off or broken skirt:
Improper steel chamfer
Off-line drilling
Section 3 Page 3-11
Drill Steel