A drilling machine which is also known as a drill press is a cutting process that uses drill bits of various sizes to cut a hole of circular-section in solid materials like metal, plastic, wood, rocks, etc. The drill bit as the cutting tool rotates, is often multi-point. This drill which rotates from hundreds to thousands of revolutions per minute is pressed against the workpiece with force. The force applied causes the cutting edge to cut off chips from the workpiece.
Drilling is a common process in the manufacturing industry, which is why all mechanical engineers must know about it. In this reading, we’ll explore what a drilling machine is, its parts, diagram, types, specifications, and how it works. We’ll also explore the drilling machine tools, advantages and disadvantages.
Let’s get started!
What is Drilling Machine?
A drilling machine is a powerful tool used to create holes in a workpiece, often used in woodworking, metalworking, construction, and utility projects. It is equipped with a drill bit, either a drill or driver chuck, and is used to make cylindrical holes of a specified depth and diameter on a workpiece. The drill bit is held in the drill press by a chuck and fed into the work at variable speeds. The speed and feed should be set properly, and coolant is provided for the desired finished part.
Drilling operations are performed on wood and metal, making it one of the most important machine tools. The machine tool was first invented to make cylindrical holes on metals, but there are different machine tools in the workship capable of creating holes.
The first hand-held portable drilling machine was developed by Wilhelm and Carl Fein in 1895, and the first pistol-grip portable drill with a trigger switch was patented by Black & Decker in 1917. Today, drilling machines are widely used in various operations, including plane drilling, step drilling, core drilling, boring, counterboring, reaming, countersinking, spot facing, tapping, and trepanning.
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Drilling Machine Parts
The major components of a drilling machine are base, column, upper arm, worktable, drill head, feed mechanism, spindle, chuck, electric motor and pulley.
Base
These parts of a drilling machine carry the entire weight of the machine and transfer it to the ground. This base is generally made of cast iron or steel due to its strength. the top of the base contains some slots to support the big jobs and the radial column is situated at one side of it. Generally, the base is bolted to the ground, and in some cases, it is supported by two or four legs.
Column or Pillar
Just as mentioned earlier column or pillar is situated on one side of the base. The radial column is mostly used due to the fact that it features a movable arm, having the possibility to move clockwise and anti-clockwise direction.
The column is also made of cast iron or steel, as the strength operation is needed so as to carry the load of the arm as well as the drill head. A sliding head table is mounted on the column so that the table can have up and down motion as required.
Upper Arm
The drilling machine part carries the drill head and the housing containing the driving mechanism. This material is also made of the same material as the base, making it have a rigid structure. Some manufacturer of drilling machine provides a guideway so the drill head can slide over the upper arm.
Worktable
The worktable is mounted on the column, it is made of cast iron. A t-slot is provided at the top surface of the table and some table contains a vice, depending on the operation to be performed. The worktable is designed to move up and down also right and left according to the job and tool arrangement. The adjustment of the table can be done by hand as well as some electrical mechanisms.
Drill Head
A drill head consists of various driving mechanisms. The drill head is mounted to one side of the drill arm and a drill chuck is mounted over it. this drill head is designed to slide up and down depending on the requirement of the job. A V belt is used to transfer the power from the motor to the pulley and from the pulley, the mechanical power is transferred to the drill head. Different speed is generated by the cone pulley mechanism as well as a gear-train mechanism.
Feed Mechanism
This drilling machine component receives power from the electric motor to the V belt and pulley. The up and down movement of the drill head is automatically fed by an electrical motor as well as manual feeding, which is done by hand. Rack and pinion can also be used to convert the rotational movement from an electrical motor or by hand to the straight-line movement.
Spindle
The spindle is a circular taper shaft that is used to hold the drill chuck. It is made of high-carbon chromium steel or stainless steel or steel alloys. The rotary motion is transferred from the drill head to the drill jigs, a keyhole is provided on the spindle. This enables the drill chuck to be changed. The rack and pinion mechanism also helps the up and down movement of the spindle.
Chuck
These parts of the drilling machine are mounted on the lower end of the spindle, which holds the drill jig. A keyhole is also provided on this component allowing the drill jigs to be changed. Unlike a lathe, drill chucks are generally self-centering and a three-jaw chuck is used. They are made with special alloy steel.
Electric Motor
In a drilling machine, a single-phase ac motor is used, it can run at a rpm of 600 to 5000. More rpm is used for high-drilling machines. The electric motor supplies mechanical power from the pulley to the spindle and allows different speeds.
Pulley or Gears
These components are used to transmit power and also for generating different speeds. A bevel gear is used mostly in a drilling machine to transmit power at an angle of 90 degrees. Pulleys are made of cast iron.
Diagram of drilling Machine
Specifications of a Drilling Machine
The specifications of a drilling machine include power source, motor capacity, drill chuck size, spindle speed, drill depth capacity, feed rate, drill bit compactibility.
Power Source
Most drilling machine predominantly rely on electricity as their source of energy, which ensures a reliable and consistent performance. Modern portable drilling machine are equip with battery which ease the usage in remote locations, adding to its convenience and flexibility.
Also some advanced models incorporate hydraulic systems to enhance power and precision for specialized applications.
Motor Capacity
Different motor capacity are incorporated on drilling machines, which caters for wide range of workloads and applications. The motor capacity varies from compact units suitable for light operations to robust machines designed for heavy operations.
The drilling machine motor capacity is typically measured in horsepower (HP) or Kilowatts (kW). With this, there is clear indication of the machine’s power output.
Drill Chuck Size
The Chuck size of a drilling machine is used to detemine the maximum diameter of the drill bit that the machine tool can accomodate. Drill chuch sizes are 1/2 inch, 3/4 inch, and 1 inch, allowing for various drilling requirements. This give the machine flexibility to handle different varietyof projects with varying hole diameter.
Spindle Speed
The spindel speed is measured in revolution per minute (RPM), which indicates the rotational speed of the drill bit. Different spindle speed is required for specific applications to achieve great result.
This is why drlling machines are designed to have adjustable speed settings, which allows the operators to customize the speed to meet the need of different materials, operations, and sizes.
Drill Depth Capacity
The drill depth capacity is the maximum depth a machine drill bit can penetrate into a workpiece material. It is required to choose a drilling machine with an appropriate depth capacity which is important for precise and efficient drilling operations.
With this machine tool specification, the drilling machine can meet the specific requirements of different drilling projects.
Feed Rate
Feed rate in a drilling machine is the speed which the drill bit make into the material during the operations. Drilling machines with adjustable feed rates gives the operator flexibility to control the drilling speed according the requirement of the materialwhich can determine the outcome of the project.
Drill Bit Compatibility
Drilling machines are designed to be incoporated with different types and sizes of drill bits. Drill bit types are twist drills, spade drills, hole saws, and step drills. Chuck size and machine configurations are used to determine the compactibility of the drill bits with the drilling machine.
Types of Drilling Machine
The various types of drilling machine are portable drilling machine, sensitive drilling machine, upright drilling machine, radial drilling machine, gang driling machine, multiple spindle drilling machine, deep mole drilling machine.
Portable Drilling Machine
This drilling machine is also known as a hand drilling machine, it is the most common and widely used by manufacturing companies. Unlike other standard tools, this machine tool is used for drilling holes in rocks, wood, metal, etc.
As the name suggests, the machine is small in size and can be carried to any work location. It works with a universal type of motor and it can drill from about 12mm to 18mm in diameter. Portable drilling machines are quite efficient and can be operated at higher speeds
Sensitive Drilling Machine
The sensitive drilling machines are also called bench drilling machines, they are used for making small holes at a very high speed. It is mounted on a bench with bolts and nuts and can be installed by hand. It also comes with a base, table, spindle, spindle, drill head, and driving mechanism.
Upright Drilling Machine
The upright types of drilling machines are specially designed for handling small to medium-sized workpieces. However, it is a sensitive drilling machine, it is heavier than a normal drilling machine. The upright drilling machines come with a spindle feed and speed, making them suitable for different types of work.
Radial Drilling Machine
These types of drilling machines are designed for making a hole in large and heavy workspaces. it supports a radial arm in the column which allows the table to move up and down in order to drill workpieces of different heights. It is also used as a rock drilling component that construction companies can easily use.
The radial drilling machine driving mechanism is at separate feed and different speeds. The position of the machine is adjusted by sliding the drill head and the gateway of the arm.
Gang Drilling Machine
the gang drilling machine has a long common table and a base like the other machines. It also contains 4-6 drill heads placed side by side, the drill head has separate driving motors for their working.
Gang drilling machines are used for operations like drilling, reaming, counterboring, and tapping. It is done by simply moving the machine back and forth. Different spindle tools are used for different operations.
Multiple Spindle Drilling Machines
When listing some of the important types of drilling machines that cause multiple spindles must be mentioned. It is designed to drill a number of holes in a workpiece or drill identical pieces as it comes with several spindles. These spindles drill all fed at the same time and also alter the distance between the axles to manage the holes in the drill.
Deep Mole Drilling Machine
This is a special type of drilling machine, designed to drill deep holes in the connecting rods, and spindles as well to the barrels of the gun. They are perfect for creating deep holes, achieved with high cutting speed and less feed and coolant must be used during the process.
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How Does Drilling Works?
In the working of a drilling, the swarf is carried away from the tip of the drill bit by the fluting of the drill bit. The cutting tip produces more chips which continue the movement of the chips outwards from the hole. Cutting fluid or coolant is sometimes applied to prolong the tool’s life by cooling and lubricating the tip and chip flow.
When using a gun drill coolant may be introduced with the drill shank, it is used mostly while drilling aluminum. The cutting fluid help to ensure smooth and accurate cutting and prevent the metal from grabbing the drill bit while drilling the hole.
When cutting soft metals like brass that can cause grabbing of the drill bit and even causes chatter. 1-2 mm can be ground on the cutting edge to create an obtuse angle of 91 to 93 degrees. This prevents chatter and instead cuts the metal. The cutting tool edge pushes away the metal rather than grabbing the metal, creating high friction and hot swarf.
On heavy feeds and comparatively deep holes, oil-hole drills are used in the drill bit. It is designed with a lubricant pump to the drill head through a small hole in the bit and flowing out along the fluting. The arrangement of a conventional drill press can be used in oil-hole drilling. However, it is more common in automatic drilling machinery, because the workpiece rotates rather than the drill bit.
In computer numerical control (CNC) machine tools are also called peck drilling or interrupted cut drilling. It is used to keep swarf from detrimentally building up when deep holes.
This peck drilling involves plunging the drill partway through the material, which is more than five times the diameter of the drill. It then retracts it to the surface, which is repeated until the cutting is completed.
Hand-Feed and Power-Feed Drilling Machine
Hand-feed Drilling Machine
The hand-feed types of drilling machines are simple and common types used in most workshops today. It is portable and a light-duty machine that is hand-fed by man’s power, using the handle. The operator can feel the action of the cutting tool as it cuts through the workpiece.
These drilling machines are available as bench or floor-mounted, they are driven by electric motors. This electric motor turns the drive belt on a pulley that connects to the spindle pulley. A hand-feed drilling machine is essentially high-speed and is used on small workpieces.
The sizes of hole drill with these machines is ½ inch or smaller. The head can move up and down on the column by losing and locking the chuck. This allows the drilling machine to drill different types of heights of work.
Power-Feed Drilling Machine
The power feed drilling machine is used in a maintenance workshop for medium-duty work, or work that requires large drills. These machines are usually larger and heavier than the hand feed. They are designed with the ability to feed the cutting tool into the work automatically. The depth can also be set at a preset to cut per revolution of the spindle at thousandths of an inch per revolution.
The capability of power-feed drills is needed for drills or cutting tools that are over ½ inch in diameter. This is because they require more force to make the hole than the force provided by hand. Speed varies from about 50 rpm to about 1,800 rpm in power-feed drills. special operations like counterboring, countersinking, reaming, etc. are achieved with slower sleep.
The sizes of this type of machine range from 17-inch to 22-inch center drilling capacity. They are usually floor mounted and they can be up to 2 inches, which is mounted into tapered Morse sockets. T-bolts and clamps are used to clamp larger workpieces directly to the table or base. While smaller workpieces are held with a vise.
Power transmission in drilling machine used to transmit power for its work, this power is supplied from the electric motor. The transmission process happens with the help of a V belt and pulley stacks, which connects the motor and the spindle. adjustment in the mechanism also helps to generate different speeds for the spindle.
The Feed, Cutting Speed & Machining Time of a Drilling Machine
In the operation of a drilling machine, the feed, cutting speed, and machining time important to achieve the desired result. Operators are expected to know the equation of these terms.
Feed
The feed is the distance a drill bit travels into the workpice with each rotation. It is also called feed rate and is mostly measured in millimetres. The range of the feed is 0.05 to 0.35 mm. A drill bit can be maintained by employing the best feed rate, which to a lay man it is by not feed too hard ot too low.
Cutting Speed
The cutting speed is the rate at which the edge tool travel through rotation. Materials are highly imparted on the drill bit cutting speed, which is why cutting speed should be consider and recommended. The cutting speed typically range depending on the material from 10/ m/min to 90 m/min. This can have impact on how much meterial is removed.
Mathematically, v=πdN1000
Here,
v = Cutting speed, in m/min
d = Drill diameter, m
N = Number of rotations of cutting tool per min
Machining Time
The machining time is the total time taken by the drilling machine to achieve the desired hole on the workpiece. It can be calculated using:
T=LN×f
Here, f = feed in m.
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Maintenance and Safety in Drilling Machine
One of the major maintenance of a drilling machine is by lubricating in between the drill bit and workpiece while working. This helps to dissolve heat and friction generated by the moving parts. Some manufacturers offer manuals for proper lubricating methods and cleaning methods.
The drilling machine is expected to clean after use and clear the chips to avoid damage to the moving parts. Ensure spindles and sleeves are free from grit to avoid damaging the precision fit. To prevent rust on the machine parts, especially the bed, the oil should be lightly coated on their surfaces.
Drilling larger holes requires some special care to avoid injuries to the operator. The part should hold one vice or join with other metal parts that will stop the workpiece from moving. It should be operating at slow speeds to avoid rapid abrasive wear on the moving parts. Lubrication should also be added more often.
When the machine is in extremely cold conditions, the machine should work at a slow speed. Allow the parts and lubricants to warm up before increasing the speed.
Safety precaution to be taken in drilling operation as it involves power equipment. It must be considered to prevent damage to the equipment, operator, and people nearby. To avoid this, serious care must be taken in maintaining and setting up the work and proper working tools should be selected. The holding device should also be in good condition to avoid damage.
Advantages of Drilling Machine
Below are the benefits of drilling machine:
- Drilling machine are much faster than manual drills.
- They are designed to be precise and accurate with consistent size and depth.
- Modern drilling machines are automated, they are capable of making large holes of consistent side, shape, and depth.
- They are used to drill different materials like plastics, wood, metal, and composites, which is why they are used in various applications and industries.
- The machines are capable of drilling different sze of holes on different workpiece.
Disadvantages of Drilling Machine
Below are the limitations of drilling machine:
- Drilling machines can be so noisy and produce vibration.
- Drilling machines have limited depth of drilling
- Operator are exposed to injury if no careful
- Machine can be expensive to purchase and maintain
- Regular maintenance is required to prevent breakdown