Drilling Machine

Presenter: G. Tulloch

Drilling machine

A power operated machine tool which holds the drill in its spindle rotating at high speeds and when actuated move linearly against the work piece produces a hole.

Safety Precautions 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 breaks inside the work

piece.

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

What is Drilling

Drilling is the process of cutting holes in metals by using a drilling machine and a drill

Drilling

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.

The most common drill used is the twist drill.

Belt drive system

Motor spindle

Belt

Quill

Spindle

Rack & Pinnion

Feed lever

Types of drilling machine.

Portable drilling machine Sensitive drilling machine Radial drilling machine Pillar drilling machine

Portable drilling machine

Sensitive Drilling Machine Drill holes

from 1.5 to 15mm

Operator senses the cutting action so sensitive drilling machine

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.

Holes of diameter 1 mm to 15 mm.

Pillar Drilling Machine

Drill holes upto 50mm

Table can move vertically and radially

Radial Drilling Machine

It the largest and most versatile used fro drilling medium to large and heavy work pieces.

Radial drilling machine

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.

Hand Drill

Pistol-grip (corded) drill

A drill in the shape of a pistol.

Commonly called electric hand drill.

Cordless drills

A cordless drill is a type of electric drill which uses rechargeable batteries.

parts

Vertical main column Base Moving drill head Work table Electric motor Variable speed gear

box and spindle feed mechanism.

parts

Heavy base Vertical column Horizontal arm Drilling head

The twist drill

or drill bit

Drill MaterialsThe two most common types are

1. HSS drill- Low cost

2. Carbide- tipped drills - high production and in CNC

Drill Bit

A drill bit is a multi-point tool and typically has a pointed end. A twist drill is the most common type used

Drill Bit

Flutes are incorporated to carry away the chips of metal.

Shank- provide the drive. Can be tapered or parallel

Body- tapers slightly in diameter from tip to shank to provide clearance

Twist drill

Twist drills are available with parallel shanks up to 16mm diameter and with taper shanks up to 100mm diameter and are made from high-speed steel.

Different helix angles are available for drilling a range of materials

Tool Nomenclature

Drill Bit

Fit in chuck

Fit direct into spindle

Drill Bit Features

The point of the drill is ground to an angle of 118 degrees

The nomenclature of the twist drill is shown

Twist drills - Helix Types

The helix angle of the twist drill is the equivalent of the rake angle on other cutting tools and is established during manufacture.

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

Helix types

Standard quick helixslow

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

Drill Bit

Wood bits

masonry

steel

Centre drills Combination drills known as centre drills

combine a number of operations in a single tool; for example …

drill and ream, drill two diameters, drill and chamfer, drill and countersink,

Centre drill

Types of cuttersReamers :-

Multi tooth cutting toolAccurate way of sizing and finishing the pre-existing hole.

Boring Tool:-Single point cutting tool.Boring tool is held in the boring bar which has the shank.

Types of cuttersCountersinks :-

Special angled cone shaped enlargement at the end of the holeCutting edges at the end of conical surface.Cone angles of 60°, 82°, 90°, 100°, 110°, 120°

Counter Bore Tool:-Special cutters uses a pilot to guide the cutting action .Accommodates the heads of bolts.

Types of cutters

TapFor cutting internal thread

Multi cutting edge tool.

Tapping is performed either by hand or by machine.

Drilling Processes

Drilling operations… Operations that can be performed in a

drilling machine are

Drilling Reaming Boring Counter boring Countersinking Tapping

Typical Drilling Processes

Reaming A reamer enters the workpiece

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

Countersinking

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 workpiece surface.

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

Counter sinking

This is an operation of making the end of a hole into a conical shape.

Cutting speed = half of the cutting speed of drilling for same hole.

Countersinking Bits

Countersinking Common included angles for a countersink

include …

Counterboring A counterbore tool enlarges

the top portion of an existing hole to the diameter of the tool.

Counterboring is often performed after drilling to provide space for the head of a fastener, such as a bolt, to sit flush with the workpiece surface.

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

Counter boring

This process involves increasing the size of a hole at only one end.

Cutting tool will have a small cylindrical portion called pilot.

Cutting speed = two-thirds of the drilling speed for the same hole.

Counterboring Bit

Spotfacing Spotfacing provides a seat or flat surface at the

entrance and surrounding area of a hole. This flat surface allows the bottom of a screw or

bolt to seat squarely with the material. Spotfacing is commonly done on castings where

irregular surfaces are found. Spotfacing may be performed on a drill press

with a counterbore of suitable size for the operation.

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

Spot facing

It is a finishing operation to produce flat round surface usually around a drilled hole, for proper seating of bolt head or nut.

It is done using a special spot facing tool.

Spotfacing

spotface

Making a sloped surface flat

To seat a nut

Back spotface

Spotting

Where holes in two parts are required to line up with each other, a technique known as ‘spotting’ is carried out. The top part is marked out and drilled.

The two parts are then carefully positioned and clamped together.

The holes in the bottom part are transferred by ‘spotting’ through from the top part.

Drilling of the bottom part can then proceed in the knowledge that both sets of holes are identical, which may not be the case if both parts are marked out and drilled individually.

Spotting

Operations in drilling machine

Operations in drilling machine

Counter bore and spot facing

Boring

It is process carried on a drilling machine to increase the size of an already drilled hole.

Initially a hole is drilled to the nearest size and using a boring tool the size of the hole is increased.

Tapping

Process of cutting internal threads with a thread tool called tap.

Tool Holding

Tool Holding devices

The different methods used for holding drill in a drill spindle are

By directly fitting in the spindle hole.By using drill sleeveBy using drill chuck

Tool Holding parallel shank drill

Drills and similar tools with parallel shanks are held in a drill chuck.

By rotating the outer sleeve, the jaws can be opened and closed.

To ensure maximum grip, the chuck should be tightened using the correct size of chuck key. This prevents the drill from spinning during use and chewing up the drill shank.

Drill bit is only gripped by the shank

The Drill Chuck

Chuck Morse Taper

Chuck Key

KeylessChuck

Drill fixed to the spindle

Tool HoldingHolding taper shank drills

Tool Holding Where a cutting tool or chuck has a Morse taper

smaller than that of the spindle, the difference is made up by using a sleeve.

Morse Taper Sleeve

For example, a drill with a No. 1 Morse-taper shank to be fitted in a spindle with a No. 2 Morse taper would require a 1—2 sleeve.

Morse Taper Sleeve

Drill Drift To remove a shank from the spindle, a taper key known as a

drift is used.

Using the drill drift The drift is inserted through a slot in the spindle

Strike here to remove

Most modern machines have a built-in drift

Workholding

Step Blocks Clamps V-Blocks Angles Jigs T- Slots Bolt

Work Holding Devices

NEVER HOLD WORK BY HAND

Drilling Machine Vice The Machine Vice

has slots in the side of the base of the vice which enable the user to screw the Machine Vice to the Drilling Machine table.

Direct Clamping

Clamping set

Vee Blocks & Clamps

used when drilling round bar

Hand Vice

used on drilling machine to clamp sheet metal

An angle plate is a work holding device used as a fixture in metalworking.

The angle plate is made from high quality material that has been stabilized to prevent further movement or distortion. Slotted holes or T bolt slots are machined into the surfaces to enable the secure attachment or clamping of workpieces to the plate, and also of the plate to the worktable.

Pilot Drilling

Pilot hole is a smaller hole drill before a large one.

Drilling holes to depth

Holes can be drilled to a particular depth by setting the depth stop on the machine

e.g. 15mm

Drilling Thin Material

Support acts as thicker material so drill point is guided through work

Cutting speed

Cutting speed for drilling is the rate at which

the tool passes over the surface of the metal.

i.e how fast the cutting tool is spinning . It is

commonly expressed in metres per minute.

Cutting speeds depend on: The material being cut Condition and strength of the tool and

machine Depth of cut Rate of feed Material of which the tool is made Availability of cutting fluid Size of the bit being used

Cutting speed selection The softer the work material, the faster the

recommended cutting speed

The hardness of the cutting tool material has a great deal to do with the recommended cutting speed. The harder the cutting tool material, the faster the cutting speed. The softer the cutting tool material, the slower the recommended cutting speed

47-91

Calculating cutting speed

Given in metres per minute spindle speed of machine (N) and

diameter of work must be known

S (m/min)= πDN/1000 Where π= 22/7 or 3.142 D= diameter of material N= Spindle speed(rev/min)

Spindle Speed

The rate at which the spindle rotates. It is commonly expressed in revolution per minute.

Calculating Spindle speed (rev/min)

D xS1000 rev/min

S (m/min)= cutting speedWhere π= 22/7 or 3.142 D= diameter of material N= Spindle speed(rev/min

Examples

Calculate rev/min required to drill a hole 15mm diameter in a piece of machine steel (CS 90)

Find the cutting speed of a 10mm diameter drill with a spindle of 178 rev/min.

5. Find the cutting speed for: Diameter 9mm. Spindle speed 180rev/min Diameter 6mm. spindle speed 20rev/min Diameter 5mm. spindle speed 160rev/min spindle speed 120 rev/min. Diameter 10mm.

6. Find the spindle speed for: Diameter 16mm. Surface speed 20 m/min Diameter 14mm. Surface speed 30 m/min Diameter 15mm. Surface speed 15 m/min.