DRILLING OPERATIONpresented by group B

Drilling.

Drilling is a machining operation for producing round holes in metallic and nonmetallic Materials.

The machine used for drilling is called drilling machine as shown in figure.

Tool which makes hole is called as drill bit. Drill bit are the tools used to cut away fine

shavings material of work piece in a rotational motion.

The most common drill used is the twist drill.

Twist drills

The drilling operation can also be accomplished in lathe, in which the drill is held in tailstock and the work is held by the chuck.

CUTTING CONDITIONS IN DRILLING

Cutting Speed (v):-It’s the peripheral speed of the drill

v = *D*N whereD = dia. of the drill in mN = Speed of rotation in rpm

Feed Rate (f):-It’s the movement of drill along the axis

(rpm)

Depth of Cut (d):-The distance from the machined surface to

the drill axisd = D / 2

Material Removal Rate:-It’s the volume of material removed by the drill per unit time

MRR = ( D2 / 4) * f * N mm3 / min

Machining Time (T) :-It depends upon the length (l) of the hole to be drilled , to the Speed (N) and feed (f) of the drill

t = L / f N min

TYPES OF DRILL MACHINE

1. Portable drill machine.2. Cordless drilling machine.3. Hand drill machine.4. Bench drilling machine or upright sensitive

drill machine5. Radial drilling machine6. Gang drilling machine7. Multiple drilling machine

Special purpose

PORTABLE DRILL MACHINE

It is used in domestic work. Its shape like a gun. Holes of diameter is approx.3to12.7mm.

A cordless drill is an electric drill which uses recharable batries.These drills are available with similar features to an AC mains-powered drill. They are available in the hammer drill configuration and most have a clutch, which aids in driving screws into various substrates while not damaging them

Cordless drills

Hand Drill

HOW TO USE A HAND DRILL

Bench drilling machine These are light duty machines used in small

workshops. Also called Sensitive drilling machines

because of its accurate and well balanced spindle. And bit is feed by hand.

Holes of diameter 1 mm to 15 mm. Its spindle Rpm is approximately 800 to 1000. The adjustment of the rpm is used by the help

of step pulley’s

BELT DRIVE SYSTEM

Parts of drilling machine Vertical main

column Base Moving drill

head Work table Electric motor Variable speed

gear box and spindle feed mechanism.

Radial drilling machine

These are heavy duty and versatile drilling machine used to perform drilling operate on large and heavy work piece.

Holes up to 7.5 cm. The range of speed of spindle 50 to 2800 rpm.

Parts of radial drilling machine

Heavy base Vertical column Horizontal arm Drilling head

GANG DRILLING MACHINE

The gang style drilling machine or gang drill press has several work heads positioned over a single table. This type of drill press is used when successive operations are to be done. For instance, the first head may be used to make hole. The second head may be used to boring . The third head may be used, along with a tapping head, to tap the hole. The fourth head may be used to reaming.

GANG DRILLING MACHINE

MULTIPLE SPINDLE DRILLING M/C

The multiple spindle drilling machine is commonly referred to as a multi spindle drill press. This special purpose drill press has many spindles connected to one main work head . All of the spindles are fed into the  work piece at the same time. This type of drilling machine is especially useful when you have a large number of parts with many holes located close together.

MULTIPLE DRILLING MACHINE

Typical Drilling Processes

CENTREING Also called center drilling, this operation drills

a starting hole to accurately establish its location for subsequent drilling. The tool is called a center drill.

REAMING OPERATION A reamer enters the work piece axially and

enlarges an existing hole to the diameter of the tool.

A reamer is a multi-point tool that has many flutes, which may be straight or in a helix.

Reaming removes a minimal amount of material and is often performed after drilling to obtain both a more accurate diameter and a smoother internal finish.

Reaming operation

COUTERSINKING OPERATION

A countersink tool enlarges the top portion of an existing hole to a cone-shaped opening.

Countersinking is performed after drilling to provide space for the head of a fastener, such as a screw, to sit flush with the work piece surface.

Common included angles for a countersink include 60, 82, 90, 100, 118, and 120 degrees.

COUNTERSINKING OPERATION

COUNTERBORING OPERATION

A counter bore tool enlarges the top portion of an existing hole to the diameter of the tool.

Counter boring is often performed after drilling to provide space for the head of a fastener, such as a bolt, to sit flush with the work piece surface.

The counter boring tool has a pilot on the end to guide it straight into the existing hole

COUNTERBORING OPERATION

SPOT FACING OPERATION

• Spot facing is similar to milling. It is used to provide a flat machined

• surface on the workpart in a localized area.

• Spot facing is commonly done on castings where irregular surfaces are found.

• Spot facing may be performed on a drill press with a counter bore of suitable size for the operation.

A proper size pilot must be used whenever this is done on the drill press.

TAPING OPERATION

This operation is performed by a tap and is used to provide internal screw threads on an existing hole.

Drill Bit

The twist drill or drill bit is made from High Speed Steel, tempered to give maximum hardness throughout the parallel cutting portion

Different helix angles are available for drilling a range of materials.

Drill Bit

Fit in chuck

Fit direct into spindle

Drill Bit Features

• SHANK

The shank is the end of a drill bit grasped by the chuck of a drill. The cutting edges of the drill bit contact the work piece, and are connected via the shaft with the shank, which fits into the chuck or sleeve.• FLUTE

Flute is a groove on drill bit start from the shank to the end point

• TangTang is flat surface on the upper side of drill bit used to release drill bit from the socket or sleeve

• Recess or neck

It is in between body and shank it is also called stamp portion from industry where the drill bit made and also mention drill bit size

• BodyThe body consist of flute,margin,body clearance and web

• Point Point is cone shaped end of drill bit which lip clearance heel and dead center

• WebWeb is most important part of drill bit it is the thickness of drill bit b/w flute.

Drill Bit Features The point of the drill

is ground to an angle of 118 degrees

each side is ground back to give " relief " of about 12 degrees to each cutting edge as shown

The nomenclature of the twist drill is shown

Twist drills Helix types

Standard quick helixslow

The helix angle of the twist drill is established during manufacture.

Helix types Drills with a helix angle of 20° — known

as slow-helix drills — are available with a point angle of 118° for cutting brass and bronze and with a point angle of 90° for cutting plastics materials.

Quick-helix drills, with a helix angle of 40° and a point angle of 100°, are suitable for drilling the softer materials such as aluminium alloys and copper

The standard helix angle is 30 degrees, which, together with a point angle of 118°, is suitable for drilling steel and cast iron.

Types of drill bits

Wood bits

masonry

steel

Precautions for Drilling machine

Lubrication is important to remove heat and friction.

Machines should be cleaned after use Chips should be removed using brush. T-slots, grooves, spindles sleeves, belts, pulley

should be cleaned. Machines should be lightly oiled to prevent

from rusting

Safety precaution Do not support the work piece by hand – use

work holding device. Use brush to clean the chip No adjustments while the machine is

operating Ensure for the cutting tools running straight

before starting the operation. Never place tools on the drilling table Avoid loose clothing and protect the eyes. Ease the feed if drill bit breaks inside the work

piece.

REFERENCES Fundamental of modern

manufacturing material processes and system by mikell p.groover

Wikipedia searches. Slides from different universties. Work-shop practice MT-236 by

MOHAMMAD GYAAS.