Bumper Sub Applications, Types & Operations
The bumper sub (Drilling Subs) is usually installed in the drill string just above the fishing tool (overshot) or safety joint.  Its presence in the string enables the operator to release the fishing tool in the event that it is needed in the fishing operations.  It will deliver the sharp downward blow that is required to release from the fish.

Splines built into the drilling jar (Mechanical
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