DRILLING MACHINE

The process of creating a cylindrical hole of the specified diameter and depth by removing metal with the rotating edges of a drill.

This machine is used to create a circular hole. In this, a tool is used to drill holes of varying sizes and other operations called a drill bit. Holes can be drilled on various surfaces from metal to wood. This machine is one of the most important machine tools.

Working Principle of Drilling Machines

The working principle of any drilling machine remains almost similar. When power is supplied to the motor, the spindle rotates, causing the attached stepped pulley to also rotate as shown in the image below.

On the opposite end, a stepped pulley is attached, which can be inverted to increase or decrease the rotational speed. A V-belt is installed between the stepped pulleys for maximum power transmission.

Now, the drill bit that was placed in the fixed workpiece is connected to the spindle. As it rotates through the rotation of pulleys, the drill bit rotates. The spindle is moved down to advance the drilling process with the help of a handwheel. After the hole is drilled, the handwheel is rotated to lift the spindle.

The final result creates a hole in the fixed workpiece.

Parts of Drilling Machine

We shall be discussing various types but each type contains the basic parts listed below. Refer to the image while studying the drilling machine parts.

Base

The whole machine is mounted and supported by the base. In the case of smaller machines, the base can either be secured to a workshop floor or mounted to a work table. Some bases have slots for holding larger workpieces that do not fit on the table.

Column

It is also called a pillar. The column is typically a hollow, cylindrical component the joins the base, table, and head. Moreover, the column functions as a linear slide on which the table is raised and lowered. It can be round or box-shaped.

Spindle

The spindle is a shaft assembly with bearings which joins the electric motor to the chuck. To guarantee that the holes that are drilled are concentric, spindles are made to have as minimal rotational eccentricity as feasible. It holds the chuck.

Stainless steel, high-carbon chromium steel, or steel alloys are used in the construction of spindles. They transmit the rotational motion of the drill head. With the aid of the rack and pinion system, it can move up and down.

Chuck

During drilling operations, the chuck is used to hold the tool tightly to prevent it from slipping. Typically, a drill chuck has three adjustable jaws to accommodate various drill bit diameters. These jaws, when adjusted, move radially inwards or outwards as they are self-centring.

Chuck is usually made of special alloy steel. It is present on the spindle's lower end.

Table

The table provides the workpiece with a stable surface. It can be lifted or lowered to alter the distance between the drill bit and the workpiece. Moreover, the table has T-slots or holes to allow workpiece clamping. They may be circular or rectangular.

Head

The spindle, the feed mechanism, and the drill chuck are all housed within the drill head. In most cases, an electric motor connected to a gearbox mounted on the head is used to drive the spindle.

Electric Motor

The electric motor can either directly drive the spindle through the use of a gearbox or indirectly through the use of a series of belts and pulleys. The electric motor can be attached to the machine in one of two locations: either the bottom of the base or the very top of the column.

Feed, Cutting Speed, and Machining Time of Drilling Machine

The operation of this machine is always followed by terms feed, speed, and machining time if the application is in an industry. These terms have specific equations associated with them. Let us learn more.

Feed

The distance the drill bit travels into the workpiece with each spin is known as the feed. Feed or feed rate is mostly measured in millimetres.

The range of the feed is 0.05 to 0.35 mm
For a given tool, the best tool life can be attained by employing the maximum feed rate.

Cutting Speed

The rate at which the edge of a tool travels is known as the cutting speed. Drilling materials have an impact on the recommended cutting speed. The typical range for the cutting speed is 10 m/min to 90 m/min. The cutting speed and feed have an impact on how much metal is removed.

Machining Time

The total time taken by a machine (lathe, drill, mill, etc) to change the dimensions of a workpiece without the direct involvement of an operator is called the machining time of that machine.

Operations on a Drilling Machine

Although drilling is the primary operation performed by this machine, a variety of similar operations are also done on holes using other tools. The following is a list of various drilling machine operations to create different types of holes.

Drilling

A cutting process that involves spinning a drill bit to create a circular hole in solid materials is known as drilling. The drill bit is typically a multi-point rotary cutting tool. The bit is pressed against the workpiece and rotated at speeds between several hundred and several thousand revolutions per minute.

This causes the cutting edge to press against the workpiece, removing chips as the hole is drilled which is shown in the schematic diagram below.

Reaming

A high-precision hole-finishing procedure carried out with a multi-edge tool is known as reaming. High penetration rates and shallow cuts involved in the reaming process enable close dimensional tolerance, excellent hole quality, and a high surface finish of the previously drilled hole in the workpiece.

Boring

A cutting process that entails enlarging an existing hole in a workpiece with a single-point cutting tool or boring head is known as boring. Sometimes, the process is done to correct the roundness of the previously drilled hole.

Counterboring

The process of enlarging a hole over a particular section in the workpiece for screw clearance using counterboring tools is known as counterboring. This creates a shallow and enlarged cylindrical cut in the upper end of the hole to make a place for the head of a screw.

Countersinking

The process of enlarging one end of the hole giving it a conical shape is called countersinking. Countersinking creates a V-shaped edge near the hole's surface. It is frequently employed for deburring drilled or tapped holes, and to ensure fasteners sit tightly in the holes.

Spot facing

A technique used to create a flat edge on a cylindrical workpiece is called spot facing. This operation involves smoothing and squaring the top surface of the hole for a nut or screw head seat. This is also possible with end-mill cutters.

Tapping

The process of creating internal threads using a tool known as the tap is referred to as tapping. This allows a cap screw or bolt to be threaded into the hole after it has been tapped.

Lapping

A type of machining in which two surfaces are rubbed against one another with an abrasive between them is Lapping. The lapping operation can be done on these machines where the main outcome of the lapping procedure is to produce truly flat and smooth surfaces.

Grinding

A machining operation that uses a grinding wheel to remove the material from a workpiece is grinding. To finish or improve the roundness of a hole that has been drilled, the machine can perform a grinding operation.

Trepanning

The process of creating a hole by removing metal using a hollow cutting tool is trepanning. This procedure is used to create big or larger diameter holes. While the hole is being created, fewer chips are removed and a large amount of material is conserved.

Drilling Machine Tools

All the operations discussed above can be done using specific tools. But the drilling machine alone has various types of drill bits for different types of holes to be created. Let’s learn more about drilling machine tools.

Flat or Spade Drill

When a twist drill is not available, a flat drill is used. It is often manufactured from a piece of circular tool steel that has been forged to shape. The cutting edge ranges from 90 to 120 , with relief at the front ranging from 3 to 8

Straight Fluted Drill Tool

When drilling brass, the twist drill frequently advances more quickly than the recommended feed, which causes the drill to pierce the metal. Using a straight-fluted drill doesn't pose this problem.

Straight-fluted drills have flutes or grooves that are perpendicular to the drill axis, mostly used to drill brass, copper, or other softer materials.

Twist Drill Tool

The twist drill is the most frequent type of drill used today. It was created by longitudinally twisting a flat piece of tool steel multiple times and then honing the surface. Modern twist drills are manufactured by machining two spiral flutes that run longitudinally around the body of the drill and are an end-cutting tool.

There are four major classifications of a twist drill: Parallel shank, parallel stub shank, parallel long shank, and taper shank.

Taper Shank Core Drill

These drills are made to enlarge holes that have already been punched, drilled, or cored. The cutting edges are machined well below the centre of the drill. Due to this, these drills cannot create a hole in a solid substance.

A chamfered edge at the tip of each flute removes the metal. Better-finished holes are produced by cored drills than by standard, two-fluted drills. Sometimes it is used to create a hole that is half the needed size, with three or four fluted drills being used to complete the rest.

Oil Tube Drill

The process where oil tubes are bored through the earth's surface using an earth drilling machine to form an oil well is called oil drilling. The tool used for this purpose is known as the oil tube drill.

Centre Drill

When drilling centre holes into the ends of a workpiece, these twist drills with a straight shank and two flutes are the tools that are employed. They are crafted in precise dimensions.

Types of Drilling Machines

We now have a fair bit of understanding of all the important terms and definitions involved in drilling operations. Let us now learn about the various types of machines available in the industry with an image of the drilling machine diagram.

Portable Drilling Machine

These are used in most workshops for making small holes.

It can be used by holding it in your hand.

Sensitive Drilling Machine

These are made for drilling small holes in low volumes.

The speed of these machines is controlled by hand by turning a wheel that moves the tool into the workpiece.

A skilled operator should be present to operate these machines, hence the name.

Upright Drilling Machine

Sensitive and upright machines are both made the same way but an upright machine is stronger.

It usually has a power feed that pushes the tool into the workpiece automatically.

Heavy-duty jobs are better done with these machines.

There are two types of this machine: Round and Box column type.

Radial Drilling Machine

The spindle of this machine is attached to an arm that can be turned around the column.

The drill head, spindle, and feed mechanism can also move along the arm in a radial direction.

Gang Drilling Machine

These machines have more than one independent column and are known as vertical drilling machines.

Each column has its drive and spindle but they are all attached to the same base as shown in the figure.

These machines can do drilling and tapping at the same time on the same base.

Multiple Spindle Drilling Machine

These machines are made to drill multiple holes into the same piece of work at the same time, using the same pattern of holes for each piece.

These machines are perfect for making a large number of identical parts.

Deep Hole Drilling Machine

These machines are used to make holes with the ratio of width to depth being 20:1.

They are usually set up horizontally so that larger workpieces can lay on their sides.

There are two types of this machine: Vertical and Horizontal type.

Automatic Drilling Machine

An automatic drilling machine is also known as CNC (Computer Numeric Control) machine.

It is controlled automatically by a computer that reads G-code, which is a set of instructions that a machine can understand.

CNC or automatic machines are more accurate and quicker

Advantages of Drilling Machines

There are numerous advantages of these machines as they are versatile, which are discussed below.

Drilling machines are designed to produce accurate and precise holes that are consistent in size and depth.
They can drill holes much faster than a manual drill.
As some of the machines are automated, they can produce a large number of holes that are consistent in size, shape, and depth.
They can be used to drill for a variety of materials, including metal, wood, plastics, and composites, making them versatile tools for a range of industries and applications.
These machines come in various sizes, which can allow them to drill larger holes or accommodate larger workpieces, increasing the range of applications they can handle.

Disadvantages of Drilling Machines

Although several advantages of these machines have led to extensive usage, there are a few disadvantages which are given below.

Most drilling machines have a limited depth of drilling, which may not be sufficient for some applications. This limitation can be due to the length of the drill bit or the size of the machine.
There is a risk of injury when using this machine, especially if the operator is not properly trained or if the machine is not used correctly. The drill bit can break or shatter, causing injuries to the operator or others nearby.
The machines can be noisy and produce vibrations.
Some machines can be expensive to purchase and maintain, based on the specifications of the drilling machine.
They require regular maintenance to ensure they are functioning correctly and to prevent breakdowns.

Applications of Drilling Machines

Due to their versatility, despite the disadvantages, these machines are used in a variety of applications across multiple industries as listed below.

In construction and engineering, these are used for drilling holes in materials such as wood, metal, and concrete.
They are used in mining to drill holes in the ground for blasting and drilling for extracting minerals from the earth.
In the oil and gas industry, machines are used to drill wells to extract oil and natural gas from underground reservoirs.
Cordless drill machines and magnetic drill machines are widely used in manufacturing for creating holes in a range of materials including metals, plastics, and wood.
These machines are also used in the medical industry for creating holes in bones during orthopaedic surgeries.
In the automotive industry, these machines are used to drill holes in metal sheets for creating chassis and other parts.

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