2. ⚫ Drilling is the operation of producing circular hole in the
work-piece by using a rotating cutter.
⚫ The machine used for drilling is called drilling machine
⚫ It is the simplest and accurate machine used in production
shop.
⚫ The work piece is held stationary i.e Clamped in position
and the drill rotates to make a hole
⚫ A Drilling machine is also referred to as Drill Press
Introduction
5. Radial Drilling Machine
⚫ Used for medium and
heavy duty operations /
applications
⚫ Heavy circular column
mounted on a very strong
base.
⚫ Radial arm mounted on
column can be raised and
lowered and also swung
around
6. Radial Drilling Machine
⚫ Drill head with drive and feed
mechanism is fitted on the radial
arm
⚫ Drill head can be moved
horizontally along the slide on
the radial arm and locked at
desired position
⚫ Rigid Rectangular table can
accommodate small to large
sized heavy work pieces
7. ⚫ Based on arm and drill head
movements RDM is classifies as :
Plain RDM
Universal RDM
Radial Drilling Machine
8. ⚫ Plain radial Drilling machine has : Vertical Movement of
arm + Radial swing of arm + Horizontal movement of
Drill head
⚫ Universal Drilling machine has : Vertical Movement of
arm + Radial swing of arm + Horizontal movement of
Drill head + Drill head tilt on two horizontal axis
Radial Drilling Machine
9. Types of Drill Bits
• According to material :
✔ High speed steel – most common
✔ Cemented carbides
- Without or with coating
- In the form of brazed, clamped or solid
• According to size
✔ Large twist drills of diameter around 40 mm
✔ Micro drills of diameter 25 to 500 μm
✔ Medium range (most widely used) diameter
ranges between 3 mm to 25mm.
10. Types of Drill Bits
• According to number of flutes
✔ Two fluted – most common
✔ Single flute – e.g., gun drill (robust)
✔ Three or four flutes – called slot drill
11. • According to helix angle of the flutes
✔ Usual – 200
to 350
– most common
✔ Large helix : 450
to 600
suitable for deep holes and
softer work materials
✔ Small helix : for harder / stronger materials
✔ Zero helix : spade drills for high production drilling,
micro-drilling and hard work materials.
• According to length – to – diameter ratio
✔ Deep hole drill; e.g. crank shaft drill, gun drill etc.
✔ General type : L/φ ≅ 6 to 10
✔ Small length : e.g. Centre drill
Types of Drill Bits
12. • According to shank
✔ Straight shank – small size drill being held in drill
chuck
✔ Taper shank – medium to large size drills being fitted
into the spindle nose directly or through taper
sockets
Types of Drill Bits
13. • According to specific applications
✔ Centre drills : for small axial hole with 600
taper end
to accommodate lathe centre for support
✔ Step drill and Subland drill : for small holes with two
or three steps
✔ Half round drill, gun drill and crank shaft drill.
✔ Oil hole drills: Oil holes running inside the body or
grooved on the body clearance of the drill.
✔ Trepanning tool : for large holes in soft materials
Types of Drill Bits
18. Twist drill is defined as an end cutting tool having one or
more cutting teeth with cutting lips formed by the
corresponding number of helical chip removal flutes. In
the past drill tools was manufactured by twisting hence,
the name Twist Drill.
Twist Drill Nomenclature
19. Straight-shank drills:
• Held in drill chuck
• Up to ½ in. in diameter
Tapered-shank drills
• Fit into internal taper of drill press spindle
• Tang provided on end to prevent drill from
slipping
Twist Drill Nomenclature
20. Body:
• Portion of drill between shank and
point
• Consists of number of parts for
cutting
Flutes:
• Two or more helical grooves cut
around body of drill.
• Form cutting edges, admit cutting
fluid, allow chips to escape hole
Twist Drill Nomenclature
21. Margin:
• Narrow, raised section on body of
drill
• Next to flutes and extends entire
length of flutes
• Provides full size to drill body and
cutting edges
Body Clearance:
• Undercut portion of body between
margin and flutes
Twist Drill Nomenclature
22. Web:
• Thin partition in center of drill, extends full length of
flutes (metal column that separates the drill from the
flutes)
• Forms chisel edge at cutting end of drill
23. Cutting Unit: The unit that cuts away the material while
drilling holes.
Cutting unit of the drill consist of 2 or more cutting edges.
It consist of
• Point of a drill: Cone shaped surface at the cutting end.
• Heel: Edge formed by the intersection of flute and the
body clearance
• Lip (cutting edge): Edges formed by the intersection of
flanks and faces.
• Lip clearance: Is the relief ground on point of drill
extending from cutting lips back to the heel
25. Tang:
• Flattened end of the
tapered shank which fits
into the socket or the drill
holder.
26. Machining Time for Drilling
Amount of material removed during drilling operation is a
function of cutting speed and feed. Cutting speed (CS)
measured as the peripheral speed of the drill.
Drill feeds are expressed in mm per revolution. Feed of the
drill is the distance moved by the drill into the work in 1
revolution.
