The conventional stand alone Gundrill Machine requires a pilot bushing held against the part to guide the tool while it enters a material. This is due to the point location not being on center. Once in the material, the Gundrill is a self-piloting tool, which floats on a thin film of lubrication supplied to the O.D. While maintaining the correct feeds, speeds, and coolant pressure, the Gundrill produces a precision hole without the need for additional qualifying operations.

High Pressure coolant systems coupled with through the spindle coolant capabilities have made it possible for Gundrilling applications to be introduced in a wide variety of Machine Tools. The most adaptable being the CNC Machining center. The pilot bushing is substituted with a pilot hole used to support the tool as it enters the material. The tolerance for this hole is .0005" larger than the tool in diameter and 1-2 times diameter in depth. A flat bottom configuration is desired for optimum entry conditions. The tool is then guided into the pilot hole while turning at 50-RPM counter clockwise to offset any misalignment between the tool, holder or part stack-up tolerances. The tool is stopped about .100" from the bottom and the coolant and RPM are turned on. The tool should be turning clockwise at this point. The feed is started with a steady consistent feed without a pecking cycle. The high-pressure coolant will evacuate the chips through the straight flute and with the correct Geometry and bearing pad combination the precision hole is obtained. When the desired depth is reached the tool is retracted to its original starting position inside the pilot hole. The RPM and Coolant are then shut off and the tool can be removed from the part.

If there is a blind hole, which requires a bottom configuration with a radius or flat bottom, this can be achieved with one single pass as well as multiple diameters.

On some applications standard three-piece construction Gundrills have been replaced with Solid Carbide Gundrills as small as .055", this yields greater rigidity, faster SFM, and increased penetration rates as much a 3 - 4 times. Coolant concentration levels should be maintained at 10% - 12%. It is recommended to consult your coolant supplier to insure that your coolant is Gundrill compatible.