Definition
Bumper Sub — A bumper sub is a telescoping BHA or fishing tool that provides axial stroke, allowing the driller to deliver controlled downward jarring blows and to maintain constant weight while working a fish or drilling from a floating rig.
Also known as: bumper sub, bumper jar
What a bumper sub does
A bumper sub is a slip-jointed tool that can stroke open and closed along its axis while still transmitting rotation and torque. That free travel lets the operator deliver a downward jarring blow — complementing the upward blow of a drilling jar — and it lets weight be applied smoothly to a fish during fishing operations. On a floating rig it absorbs heave so constant weight can be held on a tool despite vessel motion.
Role in fishing strings
In a fishing assembly the bumper sub is run below the jar and accelerator, above the overshot or other catching tool. Its stroke gives the operator the freedom to jar down to release a catch, to work the fish loose, and to space out the string so the jar and accelerator can be cocked and fired effectively.
Why it matters for rentals
Bumper subs are specialized, occasional-use tools best matched to a specific fishing or heave situation.
Find rental bumper subs among our fishing tools, or contact us to build a complete fishing string for your recovery job.