A6: Pump Open Force is a hydraulic force that results from the difference between the annular and drill string pressures. The Pump Open Force acts to open the jar and is calculated as follows: POF = Washpipe Area * Pressure Drop across the bit — (for DJ4, and DJ6 with a ported Piston Sub) POF= Piston Area*Pressure Drop across the bit — (for ST-5, and DJ6 with a non ported Piston Sub) Q7: Why should I use a shock tool? Top A7: When drilling with a tri-cone bit, it is very likely that the bottom of the hole will not be perfectly flat. Any indentation from the bit in the bottom of the hole will cause axial vibrations. This is similar to driving over a pothole with your car. When your car’s wheel rolls over the pothole, it drops vertically into the hole and then bounces back up vertically when it leaves the pothole. As a drilling bit is spinning on the bottom of the hole, if it encounters an indentation, it will drop into the indentation and bounce back out of it. This repeated movement in
