Deep hole drilling was first developed for the manufacturing of firearms, hence the name gundrilling. Originally a time-consuming and expensive process, technological advances have made it a highly efficient manufacturing process utilized in all metal cutting industries, including automotive, aircraft, aerospace, construction, medical, tool and die, petro chemical, hydraulics, pneumatics and more. Gundrilling is an ideal solution for most deep hole and high precision drilling projects. This operation produces accurate, repeatable holes with excellent surface finishes.
Gundrills hold location to precise tolerances, are sized to exact specifications, produce burr-free holes and can be formed to produce specific shapes in blind holes and bottom forming with a minimum of machine adaptation. These systems can be easily integrated with CNC machining centers, lathes and milling machines for a relatively small investment, making it affordable for large or small shops with production requirements varying from one piece to hundreds of thousands.
- Straightness tolerances : 1/1000
- Concentricity tolerances : 1/1000
- Hole diameter tolerances : IT7
- Roughness : 4Ra
- Consistent reproduction from hole to hole
Gundrilling is a metal removal process involving a drilling machine, a high pressure coolant system and a high quality drill with a single or double flute along the shank. In operation, the drill is positioned and held in the spindle nose, then guided into the workpiece through a prestarted hole or guide bushing to prevent vibration and ensure accuracy. The drill tip's cutting edges produce thin curled chips that are carried back along the shank by the high pressure coolant and deposited in the chip box. The off-center design of the cutting edges creates pressure within the bore, which is carried by pads behind the drill tip. The coolant that flushes out the chips also lubricates these pads, which burnish the surface and develop the fine finish for which gundrilling is known.
The Carbide Head is either extruded in sticks or preformed from a specific manufacturer to a designated size usually larger than the finished diameter. Carbide selection is very critical, for example, materials that are abrasive require different carbide than exotic types of materials. The proper combination of cobalt content and grain size make noticeable differences while machining. The carbide is then precision ground to size allowing for predetermined backtaper, relief depths and contours.
Once the tubes are Electro-Polished, they are Black Oxide Coated. This will increase the surface tube finish and allow better chip evacuation and eliminate the possibility of tools rusting. This process is applied to both the inside and outside of the tube.
This process is administered to all of our tubes and brings the tubes' finishes in the flute area as low as 4Ra. This will allow the chips to evacuate faster and more efficiently. This process is also applied inside the tools' coolant channel and reduces the turbulence caused by uneven coolant passages.
Our new laser etching operation is used to permanently mark the tools to assure constant identification under any conditions.
Seamless Aircraft Grade Tubing:
This method is used because of its ability to be formed and heat treated without cracks and distortion. This material is formed into the standard Vee shape or two flutes allowing for the maximum amount of clearance in the ID for coolant to flow unobstructed. The chips are evacuated down the center of the flute.
Drivers are manufactured from various materials depending on the hardness desired by a particular application. The spindles or tool holders determine the locking mechanisms prescribed for individual applications. The most common and standard is a two degree tapered flat in an under-cut centered in the driver. There are many variations subsequent to machine stroke limitations, small diameter deep hole applications require longer drivers to enable shorter tip and tube lengths. This allows for maximum surface feet per minute without the whip factor. Many machine manufacturers dictate the drivers' OD and lengths depending on the builder's geographic location hence, metric or imperil.
Driver design is important because of the high speeds and pressures used in the gundrilling process. Maximizing the gundrill driver length improves rigidity and concentricity.