Drilling Machine
Drilling
Drilling is the operation of producing circular hole in the work-piece by using a rotating cutter called DRILL. The machine used for drilling is called drilling machine.
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.
Drilling Machine
It is the simplest and accurate machine used in production shop. The work piece is held stationary ie. Clamped in position and the drill rotates to make a hole.
Types :a) Based on construction: Portable, Sensitive,Radial, up-right, Gang, Multi-spindle b)Based on Feed: Hand and Power driven
Sensitive Drilling Machine
Drill holes from 1.5 to 15mm
Operator senses the cutting action so sensitive drilling machine
Up-Right 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.
Drill Materials
The two most common types are 1. HSS drill - Low cost 2. Carbide- tipped drills - high production and in CNC machines Other types are Solid Carbide drill, TiN coated drills, carbide coated masonry drills, parabolic drills, split point
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 fixed to the spindle
Drilling operations
Drilling
Centre Hole
Drilling
Deep Holes
Drilling Thin
Material
Drilling
Pilot Hole
Tool Nomenclature
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 sleeve By using drill socket By using drill chuck
Work Holding Devices
Drilling operations
Operations that can be performed in a drillin g machine are Drilling Reaming Boring Counter boring Countersinking Tapping
Operations in drilling machine
Operations in drilling machine
Reamers :Multi tooth cutting tool Accurate way of sizing and finishing the preexisting 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.
Types of cutters
Types of cutters Countersinks :Special angled cone shaped enlargement at the end of the hole Cutting 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.
Counter bore and spot facing
Types of cutters
Combined Countersinks and central drill :Special drilling tool to start the hole accurately. At the end it makes countersinks in the work piece. Gun drill :Machining of lengthy holes with less feed rates.
To overcome the heating and short life of the normal drill tool
Types of cutters
Tapping:-
For cutting internal thread
Multi cutting edge tool. Tapping is performed either by hand or by machine. Minor dia of the thread is drilled and then tapping is done.
Work Holding Devices
1. Machine Table Vice
Work Holding Devices
Step Blocks Clamps V-Blocks Angles Jigs T- Slots Bolt
Cutting Speed (v):-
Definitions
Its the peripheral speed of the drill v = *D*N where D = dia of the drill in m N = Speed of rotation in rpm
Feed Rate (f):Its 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:Its 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.
