Gundrill Machines
Gundrill Machines are designed to provide optimum conditions for gundrill operation; the gundrilling machine’s high pressure pump delivers lubricant to the rear of the drill. The drill can be driven by the spindle or be held stationary if the work piece is rotated. During drilling, the work piece can be advanced or the drill can advance. The gundrill is supported by anti-whip devices along the shank and at the rear of the chip box. The chip box contains chip deflectors and a front end bushing, which guides the drill into the work piece. The chip box also contains escaping chips and lubricant, which are separated and filtered.
Gundrilling on CNC Machining Centers, Mills, Screw Machines, Lathes
or virtually any machine with through the spindle high pressure coolant capabilities can adapt the gundrilling process. The tool selection and operation sequence is the same as the conventional gundrill machine with the exception that a pilot hole is needed to replace the starter bushing. The general rule of thumb is one to two times diameter in depth and .0005″ larger in diameter. It is preferred that a flat bottom form is produced to eliminate the chance of deflection at the point of entry. If this cannot be obtained the pilot angle must match the outside angle of the gundrill. The truer the pilot hole, the straighter the hole. When possible, the tool should approach the pilot hole rotating backwards at about 25 RPM to compensate for any misalignment between the spindle, tool holder, or tool alignment. Once inside the pilot hole the tool will stop at about .100″ from the bottom and the coolant is turned on and RPM is started. The tool will now drill at the predetermined feeds and speeds (without pecking). At the bottom of the hole “either blind or through” the tool is immediately retracted (no dwell) to the original starting position. The coolant and RPM is shut-off and the tool may be retracted fully out of the part.