Application: Gun Drills on a Machining Center
Gun drills used to be performed on the gun drilling machines as secondary processing. When the workpieces move from the lathe/milling machine to the gun drilling machine, the following issues might be present:
Extra time spent on the removals and the re-clamping of the workpiece
Due to the variations in accuracy of machines and during clamping of a workpiece, hole accuracy is negatively affected.
Having difficulty in clamping special-shaped workpieces and having a greater chance of damaging the workpiece.
Nowadays with many machining centers equipped with coolant liquid delivery capability, the processing of deep hole drilling in diameter smaller than Dx50 could be performed directly on the lathe machine and milling machine.
Special notes on gundrilling on machining centers:
Unsupported length should be less than Dx25. A lengthy unsupported piece may cause the gun drill tube to twist and fracture.
Pilot hole is necessary. Diameter tolerance should meet ISO:F7 standard. Drilling depth is 1.5 times of the diameter.
When the gun drill enters the pilot hole, either do not rotate the gun drill, or rotate it slowly at RPM<50. After the gun drill enters the pilot hole, turn on the coolant liquid and wait for one second before rotating the gun drill.
After drilling is completed, turn off the coolant liquid and cease rotation of the gun drill, or rotate the gun drills at RPM<50. Withdraw the gun drill from the workpiece and the drilling is completed.