DRILLING MACHINE WORKING AND TYPES

DRILLING MACHINE AND ITS CONSTRUCTION AND WORKING AND TYPES

                       It is a machine which is used to drill the holes on the components or work piece with the help of drill bits. The drill bits are also called as Multi-point cutting tools which can have their rapid impact on the Material Removal Rate (MRR) i.e. a single point cutting tool(like the one used in a lathe machine) can removes the material slowly whereas, a multi-point cutting tool removes the material at a faster rate and thereby increases MRR. Drilling machine is one of the most important machine tools in a workshop. It was designed to produce a cylindrical hole of required diameter and depth on metal work pieces. Though holes can be made by different machine tools in a shop, drilling machine is designed specifically to perform the operation of drilling and similar operations. Drilling can be done easily at a low cost in a shorter period of time in a drilling machine. Drilling can be called as the operation of producing a cylindrical hole of required diameter and depth by removing metal by the rotating edges of a drill. The cutting tool known as drill is fitted
into the spindle of the drilling machine. A mark of indentation is made at the required location with a center punch. The rotating drill is pressed at the location and is fed into the work. The hole can be made up to a required depth.

Drilling machine operations
Though drilling is the primary operation performed in a drilling machine, a number of similar operations are also performed on holes using different tools. The different operations that can be performed in a drilling machine are:
1. Drilling
2. Reaming
3. Boring
4. Counter boring
5. Countersinking
6. Spot facing
7. Tapping
8. Trepanning

Construction of a drilling machine
The basic parts of a drilling machine are a base, column, drill head and spindle. The base made of cast iron may rest on a bench, pedestal or floor depending upon the design. Larger and heavy duty machines are grounded on the floor. The column is mounted vertically upon the base. It is accurately machined and the table can be moved up and down on it. The drill spindle, an electric motor and the mechanism meant for driving the spindle at different speeds are mounted on the top of the column. Power is transmitted from the electric motor to the spindle through a flat belt or a ‘V’ belt.

The parts are as follows.

1.Base(Bed):

The base is made up of Cast Iron which has the capability of high compressive strength, good wear resistance and good absorbing capability(i.e. absorb the vibrations induced during working condition) and for these reasons, it acts as a base to the drilling machine.

2.Column: It is exactly placed at the center of the base which can act as a support for rotating the Swivel table and holding the power transmission system.

3.Swivel Table: It is attached to the column which can hold the machine vice in the grips and thereby, the work piece is fixed in the machine vice to carry out the drilling operation.

The Swivel table can move up and down by means of rotational motion and can be locked to the column by means of locking nut.

4.Power Transmission system:

It consists of motor, stepped pulley, V-belt and the Spindle. The power transmission is explained in the working of the drilling machine.

5.Hand wheel:

By the rotation of hand-wheel, the spindle moves up and down in the vertical direction in order to give the necessary amount of feed to the work.

Here, the rotational motion is converted into linear motion by means of a Rack and Pinion mechanism which was explained below.

6.Chuck: It is used to hold the drill bit.

Types of drilling machines
Drilling machines are manufactured in different types and sizes according to the type of operation, amount of feed, depth of cut, spindle speeds, method of spindle movement and the required accuracy.

The different types of drilling machines are:

1. Portable drilling machine (or) Hand drilling machine
2. Sensitive drilling machine (or) Bench drilling machine
3. Upright drilling machine
4. Radial drilling machine
5. Gang drilling machine
6. Multiple spindle drilling machine
7. Deep hole drilling machine

1.Portable drilling machine
Portable drilling machine can be carried and used anywhere in the workshop. These types of a drilling machine are commonly used in all the workshops. The entire drilling mechanism is compact and small in size and so can be carried anywhere. This type of machine is widely adapted for automobile built-up work. The motor is generally universal type.These machines can accommodate drills from 12 mm to 18 mm diameter. Portable drilling machines are operated at higher speeds.Used to drill small sized holes. It is operated by holding in a hand. The work piece where the hole is to be drilled is held in a vice.

 

2. Sensitive Drilling Machine

This types of drilling machine used to drill small holes at high speeds in lighter jobs or work pieces. The machine may be mounted on the bench or floor & the drilling work is started with the drill fed into the work piece by purely hand control.

Hand-feed permits the operator to sense the progress of the drill into the work piece, so that if there is any drill worn out or jams it may be released immediately to prevent the drill bit from breaking.

Since the operator senses the cutting action at any instant it is called as the sensitive drilling machine. These machines are capable of drilling small holes of diameter as small as 0.35 mm to 15 mm. These machines run at a higher speed as high as 2000 rpm

Upright Drilling Machine

It is larger in size and stronger than sensitive drilling machine. It is used for drilling medium and large-sized holes. Based on the type of column used it is classified as a round column and box column upright drilling machines.

Radial drilling machine
The radial drilling machine is intended for drilling on medium to large and heavy work pieces. It has a heavy round column mounted on a large base. The column supports a radial arm, which can be raised or lowered to enable the table to accommodate work pieces of different heights. The arm, which has the drill head on it, can be swung around to any position. The drill head can be made to slide on the radial arm. The machine is named so because of this reason. It consists of parts like
base, column, radial arm, drill head and driving mechanism.

Construction of Radial Drilling Machine:

The setup essentially consists of

1. Base
2. Column
3. Radial Arm
4. Motor for elevating the arm
5. Elevating screw
6. Guide ways
7. Motor for driving drill spindle
8. Drill head
9. Drill spindle
10. Table

• Base: It is made up of Cast Iron which possesses high compressive strength and good wear resistance. The base is used to support the assembly of parts on it and also absorbs the vibrations induced by the machine parts.
• Column: It is exactly placed at one end of a bed which can act as a support for rotating the radial arm in 360 degrees.
• Radial Arm: It is the arm which is connected to Column. The Drill head is slided from one end to another end by the guide ways.
• Motor: It is placed on the drill head for driving the work unit(Spindle of the Drill bit)
• Table: The machine vice is connected to a swivel table which can hold the workpiece for further operation.
• Flywheel or Hand wheel: It is connected to the spindle arrangement which is used to move up and down w.r.t. the work piece.
• Drive Head: It generally consists of two levers which by varying can increase or decrease the speed of chuck.
• Chuck: One end of the chuck is connected to the spindle arrangement and another end is connected to the drill bit(tool).
• Tool-Drill bit: The drill bit is used to drill the holes on the specimens.
• Work piece: It has to be fixed in the machine vice provided on the table.

Gang drilling machine
Gang drilling machine has a long common table and a base. Four to six drill heads are placed side by side. The drill heads have separate driving motors. This machine is used for production work. A series of operations like drilling, reaming, counter boring and tapping may be performed on the work by simply shifting the work from one position to the other on the work table. Each spindle is set with different tools for different operations.

Tools used in a drilling machine
Different tools are used for performing different types of operations. The most commonly used
tools in a drilling machine are
1. Drill
2. Reamer
3. Counter bore
4. Countersink
5. Tap
1. Drill
A drill is a tool used to originate a hole in a solid material. A helical groove known as ‘flute’ is cut
along the length of the drill.
Different types of drills are
1. Flat Drill
2. Straight fluted drill
3. Twist drill
4. Center drill

Twist drills are the type generally used in shop work. They are made of High speed steel (HSS) or High carbon steel. There are two types of twist drills namely (i) Straight shank twist drill and (ii) Taper shank twist drill. The diameter of the straight shank drill ranges from 2 to 16 mm. Taper shanks is provided on drills of larger diameter.

Reamer
The tool used for enlarging and finishing a previously drilled hole is known as a reamer. It is a multi tooth cutter and removes smaller amount of material. It gives a better finish and accurate dimension.

Counter bore
A Counter bore is a multi tooth cutting tool used for enlarging the top of the previously machined hole. It has three or four cutting teeth. The flutes on them may be straight or helical. Straight fluted tools are used for machining softer materials like brass and aluminium and for short depth of cut. Helical fluted counter bores are used for longer holes

Countersink
A countersink has cutting edges on its conical surfaces. It has a similar construction of a counter bore except for the angle of the cutting edges. The angle of countersinks will generally be 60°, 82° or 90°. It is used for enlarging the top of the holes conically.

Tap
A tap has threads like a bolt. It has three to four flutes cut across the threads. It can cut threads on the inside of a hole. The flutes on the threads form the cutting edges. It is a multi point cutting tool. It will dig into the walls of the hole as the lower part of the tap is slightly tapered. The shank of the tap is square shaped to enable it to be held by a tap wrench.

Applications of Drill Machines

The basic function of drill machine is to construct hole of different size in solid materials. Different drills are used for industry particular applications. Drill rigs are used to drill water wells and oil wells. Hand drills are used for screwing and fastening. Electrical pistol grip drill is used in general masonry workings by builders, electricians and plumbers. Hammer drill is particularly used by carpenters to drill and fix the wooden parts.

Cordless drills are useful where electrical provide is not feasible to get for drilling. Pillar drill machine (also referred as drill press) is used in marketable applications where it required bulk manufacture of drilled materials in a selection of size and shape like metal sheets, plastic, wood, glass and physical construction applications. The orientation based power supply is easily controlled in drill press to increase or decrease the drilling speed and capacity.

The capability of drill press differs with pillar diameter, spindle nose, spindle travel, spindle speed and electronic motor used in the machine. These are extensively used in automobile, printing and engineering field to increase the constancy and tensile power of the machine with efficient moving out to the resistive materials with quality performance. Milling cum drilling machine is broadly adopted in the industries where required mixing and grinding of solid and liquid substances.

Maintenance :

Test lubricant frequently– Lubrication reduces friction around moving parts. Scheduling regular lubrication extends the drilling machine productive life. It is also important to check that you use the right lubrication.

Check for wear and tear– Vibration, friction, high temperature and shock contribute greatly to the breakdown of drilling machines. Checking for wear and tear allows you to detect and replace faulty parts as soon as they are noticed. 

Clean the machine– Drilling machines have many seals and filters. Regular inspection ensures they are in working condition. Filters should also be changed regularly, and breathers kept clean to prevent creation of a vacuum which might suck contamination into the cab. Workers using the machine should also ensure all the holes in the machine are cleaned.

Sharpen the drilling components– Drilling machinery that has sharp, cutting, and slicing components must be sharpened. Dull cutting components compromise production and reduce efficiency. 

The sharpness of a machine part also affects the shape and accuracy of the materials that are cut. Ensure all drill bits, end bills, precision cutters, and lathe tools are kept sharp. 

Check alignment specifications– Drilling machines often have multiple components. Losing alignment can greatly affect the quality of work. You can check alignment by performing a test job and subsequently measuring the resulting parts. If the specifications are inaccurate, you will need to realign the machine.

Good records of maintenance and repair schedules– Some parts such as fluids, electrical systems and tracks have to be checked frequently for preventive measures. Keeping proper records allows you to have the tools and spare parts necessary on hand to avoid extended downtime. 

Maintenance records are also important for your employees’ safety. Preventive maintenance schedules diminish the machine downtime significantly.

Safety Precautions:

• Always wear an eye protection when using your drill.
• Make sure that cutting tools are running smoothly before starting the operation
• Never place tools or even equipment on the drill table
• Keep your guard while operating
• Adjusting the machine while using it can be dangerous, make sure to adjust it while the machine is not running.
• Use a brush to clean away the chips

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