There is more than meets the eye when drilling a hole aimed to be used in the aerospace industry. Holes come namely in all sizes and shapes and the drilling equipment and techniques to get them right vary. Here is your guide to the more than you could imagine complex world of holes and how to make them just right.
Drilling a hole for an application in the aerospace manufacturing industry is not easy. Instead, it is a complicated undertaking where different materials, operational conditions and technical requirements come together to form a serious challenge. Because of this, holes come in all sizes defined by several parameters, including its diameter, length, and tolerance. The diameter of the hole refers to the width of the hole, while the length, defined by the thickness of the material, is the distance between the two sides of the material. The tolerance refers to the maximum and minimum acceptable deviations from the desired size of the hole.
Aside from the size, holes also come in all shapes and forms. Straight, taper, pilot, and temporary holes, all which are defined by their shape. Straight holes are cylindrical and have the same diameter throughout their length. Tapered holes, on the other hand, have a larger diameter at one end and a smaller diameter at the other. Pilot holes are holes with a small diameter that are drilled before drilling the final hole to guide the drill bit. And finally, there are the temporary holes that are intended to be filled or plugged after use.
Drilling processes to get it just right
Choosing the appropriate drilling process is crucial to achieve the desired and correct hole. The most common drilling process involves a drill bit entering the workpiece axially to cut a blind or through hole with a diameter equal to that of the tool. Twist drill bits are the most commonly used for drilling holes, but other types of drill bits, such as step drill bits and hole saws, can be used for larger or irregularly shaped holes.
Reaming is a process used to enlarge an existing hole to the diameter of the tool and obtain a smoother finish. It removes only a small amount of material and is typically performed after drilling to achieve a more accurate diameter and a smoother internal finish. Tapping is the process where internal threads are cut into an existing hole. The existing hole is usually drilled by the required tap drill size that will accommodate the desired tap.
Counterboring and countersinking are processes used to enlarge the top portion of an existing hole. Counterboring is performed after drilling to provide space for the head of a bolt or a screw to sit flush with the workpiece surface, whereas countersinking is used for screws and allows the screw to sit flush with the workpiece surface without protruding.
Some final advice
With so many variable parameters to meet, it is not surprising that it can be difficult to get a hole completely perfect the first time. Actually, it is not uncommon that it requires several sequential drilling processes one after the other to achieve the final and perfectly accurate hole. By understanding the different drilling processes and their specific application areas and matching them with the right tools for the job, you are well underway to creating the perfect hole. On the very first try.
Aerospace Drilling Pocket Guide
To get the whole story behind the art of drilling holes in the aerospace manufacturing industry check this pocket guide
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