Both bits connect with the casing pipes, just the different of thread & ID. The casing shoe bits' ID size can thru core barrel, the casing bits ID is small and can't thru the core barrel.

Casing bits can drilling and then coring. The casing shoe bits alongwith the casing pipes to drill together, the coring rock stay in the casing pipes, after the casing pipes drilling, then to drill use the core barrel which inside in the casings.

Use casing bits drilling, when core barrel coring must extract the casings & casing bits to change to casing shoe bits, and then put the core barrel.

Use casing bits drilling can't put the core barrel, however because of use the casing bits to coring, the integrity and core recovery will be better, so the coring will be choose to use casing pipes & casing bits in the soft formation and shallow hole, and change to core barrel after in the hard formation, the casing pipes must be in the hard formation.

Notes:

Imp. - Impregnated Diamond Type

S.S. - Surface set Diamond Type

T.C. - Tungsten Carbide Type

E.P. - Electroplated Diamond Type