usual wear should provide clues as to what features need additional strength. 

 Bit selection should be based on these observations. 



EXAMPLES OF BIT WEAR The following illustrations are representative 



of a few typical worn bits. Figure 29-3 shows 

 a bit that has undergone excessive wear and rounding of the gage surface. It 

 is a medium-soft formation type having interruptions of the gage teeth. These 

 interruptions reduce the amount of hardfacing available for resisting gage wear. 

 This bit has a small amount of offset and consequently is more vulnerable to 

 this type of wear because offset produces a wiping action at the gage. Such wear 

 indicates that the formation was too abrasive for this particular bit, or that the 



Figure 29-4. A bit showing extreme gage wear. 



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