As a good practice, the diameter of surface set bits and reaming shells should be measured on a regular basis to ensure that hole size is maintained. As a general rule, all holes should be collared with a full gauge reaming shell. On deeper holes, two or more shells should be alternated in the hole to maintain the hole size. Boart Longyear recommends that reaming shells be gauged every trip out of the hole.
The practice of gauging bits is more common with surface set bits. Impregnated bits typically maintain their gauge until they are fully consumed.
