Figure 29-12. A bit showing normal wear from soft formation. 



amount of undergage hole drilled will have to be reamed by the next bit. There 

 is not enough of the cutting structure left on this bit to be of use in selecting 

 of the next bit type. 



The bit shown in Figure 29-12 is considered to be in a desirable dull condi- 

 tion for a soft-formation type, except that there appears to be considerable life 

 still remaining in it. It will be noted that there is no tooth breakage and very 

 little tooth chippage. The hardfacing has very effectively protected the tooth 

 flanks from wear. Also, the pattern of hard facing has been effective in causing 

 the teeth to wear so that they have remained relatively sharp, even though an 

 appreciable amount of tooth height has been worn away. This condition repre- 

 sents a good selection of bit type and operating conditions for the formation 

 being drilled. 



652 



