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.
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