< Drilling Jars
Hydraulic-Mechanical Jars
Hydraulic Jars


Jars are tools used to apply strong impacts to stuck drill strings from the top down or from the bottom up. Currently, jars are divided into fishing and drilling jars. For more than 80 years, jars have been widely used in the drilling industry as an affordable means to increase the service life of rigs and to protect drill strings and wellbores from damage if the string stucks. Advances in technology and a clearer understanding of the dynamics of successful jar operation have made it possible for Wenzel Downhole Tools to improve the design and to optimize the operation of their jars.

Jars are moved by the conversion of the pipe string power when it is stretched during the jar operation delay. The jar impact power depends on the following factors:

  • Jar stroke length 
  • Friction in the hole
  • Number of loading elements attached above the jar (lightweight drill pipes or drill collars)
  • drill string stretching
  • Load applied to the string before the jar operation 

Drilling Jars

Standard sizes:
  • 203 mm
  • 165 mm (168 mm)
  • 121 mm

Different standard sizes of hydraulic and hydro-mechanical drilling jars allow their use as part of a drill string during drilling and for the elimination of sticking in a wide range of impact loads.