Drilling machine By Polayya ( Asst Prof, Mech Dept) Lendi Institute of Engineering &Tech
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Drilling machineBy
Polayya ( Asst Prof, Mech Dept)Lendi Institute of Engineering &Tech
Introduction Drilling is a metal cutting process carried
out by a rotating cutting tool to make circular holes in solid materials.
Tool which makes hole is called as drill bit or twist drill.
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.
Types of drilling machine. Portable drilling machine Bench drilling machine Radial drilling machine Upright Drilling machine Gang drilling machine Multiple drilling machine
Portable 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.
Bench drilling machine
parts Vertical main column Base Moving drill head Work table Electric motor Variable speed gear
box and spindle feed mechanism.
working Work piece with the exact location marked
on it with the centre punch is clamped rigidly on the work table.
spindle axis and center punch indentation are in same line.
Machine is started and drill bit is lowered by rotating feed handle.
Drill bit touches the work and starts removing material.
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.
parts Heavy base Vertical column Horizontal arm Drilling head
working Work piece is marked for exact location and
mounted on the work table. Drill bit is then located by moving the radial
arm and drill to the marked location. By starting drill spindle motor holes are
drilled.
Up-Right Drilling Machine Drill
holes upto 50mm
Table can move vertically and radially
Drilling And Drills
Types of drills– Twist drill: most
common drill– Step drill:
produces holes of two or more different diameters
– Core drill: used to make an existing hole bigger
Drill MaterialsThe two most common types are
1. HSS drill- Low cost
2. Carbide- tipped drills - high production and in CNC
machinesOther types areSolid Carbide drill, TiN coated drills, carbide coated masonry drills, parabolic drills, split point drill
Tool Nomenclature
Drilling machine operations Reaming Boring Counter boring Counter sinking Spot facing Tapping
Reaming It is a process of smoothing the surface of
drilled holes with a tool. Tool is called as reamer. Initially a hole is drilled slightly smaller in
size. Drill is replaced by reamer. Speed is reduced to half that of the drilling.
Reaming
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.
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.
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.
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.
Tapping Process of cutting
internal threads with a thread tool called as tap.
Tap is a fluted threaded tool used for cutting internal thread
Cutting speed is very slow.
Types of cuttersReamers :-
Multi tooth cutting toolAccurate way of sizing and finishing the pre-existing hole. Accuracy of 0.005mm can be achieved
Boring Tool:-Single point cutting tool.Boring tool is held in the boring bar which has the shank.Accuracy of 0.005mm can be achieved.
Countersinks :-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.
Step Blocks Clamps V-Blocks Angles Jigs T- Slots Bolt
Work Holding Devices
Definitions Cutting Speed (v):-
It’s the peripheral speed of the drillv = *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 axis
d = 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
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 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.
Thank you
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