GUNDRILLS USER GUIDE When using a gundrill on a lathe machine, a Drill Penetration Instructions short solid carbide centering drill should be used prior to the gundrill. Once the gundrill 1 Rotate the drill counterclockwise prior enters the pre-drilled hole, it is self-guided. to and during hole penetration 1 Drilling a pre-hole (drill diameter +0.02 mm) 2 Stop the drill rotation and start the coolant Never try to penetrate the workpiece by using a gundrill 3 Rotate the drill clockwise prior to drilling operation 2 Gundrill penetration through the pre-hole The influence of a Tool vs. Workpiece rotation A shallow pre-hole can’t lead the unbalanced gundrill Rotating tool Rotatingworkpiece Rotating tool& workpiece 2 x D min Worst Medium Best The maximum misalignment between the drill bushing and the workpiece center line should not exceed 0.02 mm (.0008”). Rotating Workpiece Bushing Stationary Drill Max. 0.02 mm .0008" 298 ISCAR