1. n. [Drilling]
A weak spot in the drillstring. Such a weak spot sometimes is intentionally put into the drillstring so that if tension in the drillstring exceeds a predetermined amount, the safety joint will part and the rest of the drillstring will be salvageable. A safety joint is commonly included in fishing strings and drillstem testing equipment, where the fish may be successfully caught by the fishing assembly, but tension to free the fish may prove insurmountable. By having the safety joint in the hole, the fishing company representative knows where the fishing string will part and what will be needed to latch onto the top of this additional fish.