IADC CODE 3-1-1
Non-sealed ball and roller bearing
FORMATION
Hard, semi-strength and abrasive(hard sands, cherty limestone, dolomite, cherts).
CUTTING STRUCTURE
The TO31 has slightly short, closely spaced teeth for maximum strength. No deletions or interruption on the heel teeth rows. No hard metal is applied on the inner row teeth to minimize tooth breakage because of embrittlement of welding.