Drilling is a cutting technique that makes a circular cross-sectional hole in solid materials using a drill bit when pressed against the workpiece. The drill bit—typically a rotating tool rotates at hundreds to thousands of revolutions per minute. By removing chips from the hole, the procedure ensures successful drilling. When drilling a hole in a rock, the drill bit is usually hammered into the hole with swift strokes.
Chips are removed from the workpiece by the cutting edge due to the force applied. Since drilling is frequently used in manufacturing, all mechanical engineers must to be familiar with it. Well, in this reading, we’ll explore what drilling is, its applications, operations, and how it works. we’ll also look at its safety preclusions
Let’s get started!
What is Drilling?
The process of drilling involves creating cylindrical holes on a workpiece with a predetermined diameter and depth. It is accomplished by using a drill’s rotating edges to remove metal. A drilling machine is the piece of equipment that makes the circular hole.
The holes are drilled using a specialized tool called a drill bit. Drilling holes of various sizes and operations is accomplished with these tools. Drilling is one of the most significant machine tools since it is frequently used on workpiece materials like metal and wood.
This procedure removes chips from the hole. When drilling rock, a drill bit is hammered into the hole with short strokes. Drills used for horizontal drilling are called drifter drills. Rarely, properly constructed drill bits can be used to create holes with non-circular cross-sections, such as square ones.
The machine tool was first invented to make cylindrical holes in metals, although there are different machine tools in the workshop that are capable of creating holes. Wilhem and Carl Fein of Stuttgart, Germany, in 1895 developed the first hand-held portable drilling machine. In 1917, Black & Decker patented the first pistol-grip portable drill with a trigger switch, which is still highly in use today.
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Applications of Drilling
Drilling machines are available in different shapes and sizes, varying from small hand-held power drills to bench-mounted and finally floor-mounted versions. They are used to carry out operations such as countersinking, counterboring, reaming, spot facing, as well as tapping large and small holes. Due to the fact that drilling machines can perform the operations, principles, and drill bits achieving them totally varies.
Applications of drilling machines with the use of drill bits with sharp cutting edges are used to achieve various hole sizes on operations mentioned above. The operator must know how to set up the work, set speed and feed, as well as coolant to obtain a quality hole.
However, drilling machines are used in various industries such as:
Construction and engineering to drill holes in materials such as concrete, wood or metals. They are used in mining industry to make holes in the ground for blasting and extration of minerals form the ground.
In the oil and gas sector, drilling is done to drill wells and draw natural gas and oil from underground reservoirs. Additionally, magnetic drill presses and cordless drills are often used in the manufacturing sector to drill holes in materials including wood, plastic, and metal.
Drilling machines are used in the medical field to drill holes in bones during orthopedic surgeries. Lastly, machine tools are widely used in the automotive sector to drill holes for a variety of parts, including chassis.
How Does Drilling Works?
Drilling through metal is a common task for DIYers, and the tools and methods used are similar to wood drilling. The best drill bits are the same standard bits that work for wood, and following basic safety tips and using the right techniques is crucial.
Drill bits for metal drilling can be found in various materials, including wood and plastic. High-speed steel (HSS) is the least expensive twist bit, suitable for most metal-drilling tasks. To create a center punch, measure and mark the desired hole, then use a center punch and hammer to create a small dimple. Lubricated bits last longer, as they reduce friction and heat buildup, making drilling easier and extending the lifespan of the bits.
To start with a small hole, drill successively larger holes with your drill bit for metal until you reach the desired size. Most twist bits are available in sizes up to 1 in. in diameter, but starting with a 1/4 in. hole will yield the best results. After drilling a hole in metal, it’s important to remove any sharp edges or burrs left behind. You can buy fancy deburring tools to smooth sharp edges, but a simple trick involves gently hand-twisting a slightly larger twist bit over the top of the hole to smooth out the edge and grind away any burrs.
Drilling through metal requires a variety of tools and techniques, including using drill bits, creating a center punch, and deburring the hole. By following these guidelines, you can ensure a successful and efficient drilling process for any metal material.
How to Drill a Hole?
To use a drill bit for drilling holes, follow these steps:
1. Determine the location of screws and ensure straight lines are level. Mark each hole with a pencil using a tiny X or dot.
2. Power up the drill and adjust the torque to suit the material you’re drilling. Find the Xs or dots to mark the hole, and ensure the drill is at the correct level. Stabilize the drill vertically and pull the trigger to start drilling at a low speed.
3. Once the hole is drilled as far as needed, put the drill in reverse and pull the trigger and back out the drill bit.
4. Use a drill for inserting a screw into a pilot hole. Power up the drill, adjust the torque, and fit the screw into the slot on the drill bit. Line up the screw with the hole, ensure the drill is vertical, and pull the trigger on the drill to press gently into the screw.
5. Stop drilling when the screw is completely inserted, and if you’re concerned about over-screwing, stop before the screw is completely inserted. Finish with a screwdriver to ensure a smooth and efficient drilling process.
Drilling Operations
The types of drilling operations are drilling, core drilling, step drilling, boring, reaming, counter boring, counter sinking, spot facing, tapping, and trepanning.
Drilling Operation
This is the most common operation done with a drilling machine. It is applied when a circular hole of any size is needed in a workpiece. Although one can use a lathe machine for drilling.
Core Drilling
Cores are used when sand casting is made to displace the metal where metal is desired. The molten metal flows around the core and after it solidifies the casting is removed from the mold and the holes are created on the core spaces. The hole here is quite rough and will require a heavy body drill to clean the holes.
Step Drilling
In this drilling operation, more than one diameter can be ground on the drill body, which serves as an extra operation
Boring
Boring is done to enlarge the diameter of an existing hole of a part. The tool used in this operation is generally a single-point cutting tool.
Reaming
This is the finishing of a drilled hole in order to obtain the specific size, and fine surface, and make the diameter the same size from end to end. A sufficiently smooth hole is desired and called will be called a precision hole as greater accuracy is required.
Counter Boring
Counter boring is when another drill bit of a larger size than the first will be used to open a wider hole. It is said to be used as a counterbore when the operation is done on a drilling machine. The small diameter on the end of the tool known as the pilot keeps the counterbore concentric with the original hole. This pilot is interchangeable with other different sizes to fit the various sizes of holes.
Counter Sinking
The drilling machine performs this operation to produce an angular surface at the end of a hole. It is made of different angles and diameters sizes. The angle size depends on the countersinking purposes. Countersink for a flathead screw requires an 82-included angle, keeping the center hole at an angle of 60. Different rivet head types included angles from 90 to 145-degree
Spot Facing
Spot facing is done in order to create space for a bolt head, washer, or nut. It is usually performed on casting, machining a flat or circular surface around the workpiece. However, counterbore may be used for the operation.
Tapping
This drilling machine operation is done by creating a tapped (threaded) hole on a workpiece. It is achieved by producing a non-tapped hole in the material, using a specified size drill bit. A tapping attachment will then be used to create the threading using a standard drilling machine. This tapping attachment is held in the spindle of the drill press, which accurately centers on the drilled hole.
Trepanning
Trepanning is a hole-making operation, producing an annular groove making the center a solid cylindrical core. In this operation, a cutter consisting of one or more cutting edges is placed along the circumference of a circle in order to achieve the annular groove. Trepanning is said to be feasible if the hole has a diameter of more than 50mm.
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The Difference Between Drilling, Boring and Reaming
Drilling, boring, and reaming are three distinct processes performed by manufacturing companies to create and modify holes in a workpiece. Drilling is a cutting process where a drill bit is used to cut a circular-shaped hole in a material, using a rotary metallic material called a “drill bit” with a sharp tip that aids the cutting. This drill bit scrapes away material when the drilling machine is pressed against the workpiece, ensuring drilling can be done on harder materials as long as the drill bit is hard enough to enter the workpiece.
Boring is a different operation that involves the use of a single-point cutting tool or boring head to enlarge an existing hole in a material. It is typically performed on a lathe, milling machine, or a horizontal boring mill. The difference between drilling and boring is that drilling is performed to create an initial hole in a workpiece, while boring is done to increase the diameter of an existing hole in a workpiece.
Reaming is another cutting process that uses a rotary cutting tool to create smooth interior walls in an existing hole in a workpiece. The primary purpose of reaming is to create smooth walls in an existing hole, and most manufacturing companies perform this operation mostly on a milling machine or drill press.
The major difference between drilling, boring, and reaming is quite simple: drilling creates a new hole, boring increases the diameter of an existing hole, and reaming cuts a fine interior wall on an existing hole. These processes are essential for creating holes for bolts, screws, dowels, alignment, fitment, or assembly purposes, as well as precision fitting and achieving exact tolerance requirements.
Safety Precaution While Drilling Shop
Proper eye protection is crucial when drilling metal, as it only takes one tiny metal fragment to cause a serious eye injury. To protect your eyes, choose safety glasses that wrap around the sides of your face. Lubrication is essential for drilling holes in steel that’s 1/8 in. or thicker, as it reduces friction and heat buildup, making drilling easier and longer-lasting.
Choose the right drill bit for metal, with most general-purpose twist bits being made of high-speed steel (HSS). Black oxide or cobalt steel drill bits are recommended for hard, abrasive metals like stainless steel or cast iron, as they bore more holes before becoming dull. Some bits also have a special coating called titanium nitride (TIN), which helps resist heat and friction better, making them last up to six times longer than standard high-speed steel bits.
Use clamps or vise to securely hold down your workpiece, never holding a piece of metal in one hand while trying to drill through it with the other. Start with a small hole and drill successively larger holes with your drill bit for metal until you reach the size you want. Deburr the hole after drilling a hole in metal by using a twist bit slightly larger in diameter than the hole you just drilled, gently hand-twisting it over the top of the hole.
Drill at a slow speed, as the faster a bit spins, the hotter it gets, and heat dulls bits quickly. For hard metals like steel and larger drill bits, 350 to 1,000 rpm is recommended.
For clean, precise holes in thin sheet metal, make a wood sandwich by sandwiching the sheet metal between two pieces of wood and clamping everything down on a table or workbench. The wooden “bread” layers of the sandwich keep the sheet metal flat and prevent the drill bit from wandering as it bores through the sheet metal.
Step drill bits are designed to drill holes in sheet metal and other thin materials, making them perfect for creating perfectly sized, clean holes in steel junction boxes, electrical service panels, or stainless-steel sinks. However, step bits are more expensive than regular bits.