Key components on gun drilling machine

Drill bushing – Primary function of drill bushing is momentary, but critical.

The gun drill bushing is made from thru-hardened tool steel (or carbide) and heat treated ti 61-65 RC. The ID, OD and  Face of bushing are ground concentric and square within .0002” (.005 mm) TIR.

The bushing must be in tight contact with the part. If the bushing is not “sealed” with the workpiece surface, the gun drill will start to “walk”, causing a bellmouth hole and potential tool breakage. The bushing is also perform a secondary function by supporting the gun drill shank to prevent it from whipping.

Gun drill bushings are very special tooling and play the most critical role in gun drilling machine. Standard off the shelf ones may not satisfy the process requirements. This is especially true in high volume auto parts productions with required CPK of 1.33 or higher.

Chip box - The chip box is a precision-machined component that maintains critical alignment between the gun drill bushing and drill spindle centerline.

As the chips are flushed out of the opening by the cutting fluid flow, a feature in the machine structure redirects the chips and fluid from the gundrilling operation, while containing it for a clean, mess-free gundrilling machine and surrounding area.

Chip deflector – Sometime it is called Seal disc It is molded from a specially formulated plastic material.

It was tightly fit onto gun drill shank inside the chip box to deflect chips and coolant into chute lead to machine bed for filtration. Sometimes the material is bonded to steel disc to increase resistance to chips and coolant.

Whip guide – the function of the whip guide is to stabilize the gun drill to minimize the whip.  

The whip guide is made from high strength nylon with a center hole with size equal to gun drill diameter. The number of whip guides used on the gun drilling machine varies depends on the application, typically is one for each 12 to 20 inches (300 to 500 mm) of gun drill length.

High pressure coolant System

The reliability and performance of the gundrilling process depends heavily on the machine coolant system. A logically designed reservoir system starts by holding coolant, and a high-volume pump groups works to delivery the cutting fluid to the gundrill tool. Once the coolant progresses through the metal cutting operation, it is enters the filtration system. Low-micron coolant filtration, and filter condition feedback prevent the accumulation of chips and small particles, leading to less down time, longer tool life, and improved surface finishes.

Coolant Temperature Control

The drilling headstock, the drilling process and coolant pumping system generate heat, which can have a negative impact on drilling factors such as tool life and accuracy, as well as the operating conditions around the machine. To manage the heat, either a heat exchanger or chiller is required to maintain cutting fluid at the proper temperature.

· The majority of precision gun drill drilling machines built by HTT today rotate both gun drill and part. With a properly designed machine and fixturing, it’s possible to precision-drill holes with depth-to-diameter ratios of 100:1, 200:1, and even 400:1.

HTT gun drilling machine offers many advantages, some of which are unattainable with any other machining technique. These advantages are:

○ Straightness, Drift, and Depth of Hole

○ Close Tolerance of Hole
○ Surface Finish
○ Productivity
○ Unique Capabilities