Gun drilling is the process used to produce deep and straight holes in a number of hard materials. The main difference between a gun drill and a conventional twist drill lies in the unique head geometry; a standard gun drill is characterized by a single effective cutting edge. The gun uses guide pads to burnish the hole while drilling which gives a perfectly straight hole. The result is usually a round hole with a precision diameter.
The name “gun drilling” actually comes from the initial intention; these guns were originally designed to help in drilling gun barrels. In fact, to this day, gun drills are still used extensively in the armament industry. However, these guns are now widely used in other industries such as in oil, gas, and energy exploration. They are similarly used by; engine manufacturers, plastic injection molds, and diesel fuel components.
In the oil and gas industry, particularly in Thailand, Singapore, and Malaysia, the drills are used to bore thin straight holes. Holes deeper than 20:1 often require dedicated drilling to ensure process reliability and the highest productivity. Gun drills have proved very effective at this task.
There is also a clear difference between gun drilling and BTA drilling. Gun drills, just like BTA drills introduce a coolant and also remove chips. However, the ways these processes are accomplished differ slightly. Typically, a gun drill will introduce a coolant through a small hole within the tool. Chip removal is accomplished using a groove located outside the tool. BTA drilling, on the other hand, has fluid enter the tool through a mechanism around the tool. Chips are usually removed through the drill itself. However, a time comes when BTA drilling would be preferred over gun drilling. For example, when drilling around a 50mm hole diameter, a BTA drill would be preferable.
Gun Drilling Specifications
Any gun drilling process must meet certain specifications. Without following these specifications, it might be very difficult to maintain straightness and precisions when drilling extremely deep holes. For larger holes, the BTA drill should be used.
• For 1-3mm diameters, the gun drill can be used. However, proper equipment is necessary.
• For 3mm to 25mm diameters and even 25mm to 50mm diameters, the gun drill will work perfectly.
• For 50mm to 70mm diameters, the BTA drill would do a better job compared to a gun drill.
In terms of depth, 5:1 holes should be drilled using common twist drills. 10:1 holes require high performance twist drills with through-tool coolants. The same applies for 20:1 holes. For 100:1 and 200:1 holes, gun drilling tools on dedicated and high performance gun drilling machines are required respectively. Lastly, 400:1 holes require extreme drilling range.