Definition - What does Vise Dies mean?
Vise dies are inserted into the vise jaws on a horizontal directional drilling (HDD) machine to hold the drill string stationary. This ensures properly torquing of a new drill pipe when the HDD machine runs out of track. Vise dies are used to provide a custom fit to the drill pipe being used and to avoid wear on the vise jaw itself, which is substantially more expensive to replace.
Trenchlesspedia explains Vise Dies
The forward end of drill pipes are threaded pin ends (male threaded end) and the aft is a threaded box end (female threaded end). As the hole is lengthened through directional drilling, the machine will eventually run out of track and require more drill pipes to be added. To lengthen the drill, the operator secures the drill string with the vise jaws (and dies, which are inserted in the jaws) in order to provide the necessary torque to disconnect, or break-out, the drill string from the HDD machine driver. The new drill pipe is then placed into position and the operator threads the threaded pin end of the driver into the box end of the new drill pipe. The operator continues threading until the driver and new drill pipe are mated with the drill string and proper make-up torque is reached. The vise jaws then release and the drilling continues.