Contents
• Milling Machines: types of machines,
horizontal, universal, vertical, Cutters and
their applications, Operation on milling
machines, Use of dividing head and circular
table. Direct, simple, compound, differential
and angular indexing and helical milling
operation. Table feed in milling. Work holding
devices.
What is Milling Machine?
• A milling machine is a machine tool that removes metal as the work is fed against a rotating multipoint cutter.
• The milling cutter rotates at high speed and it removes metal at a very fast rate with the help of multiple cutting edges.
• One or more number of cutters can be mounted simultaneously on the arbor of milling machine. This is the reason that a milling machine finds wide application in production work.
• Milling machine is used for machining flat surfaces, contoured surfaces, surfaces of revolution, external and internal threads, and helical surfaces of various cross-sections.
• In many applications, due to its higher production rate and accuracy, milling machine has even replaced shapers and slotters.
Principle of Milling operation
• In milling machine, the metal is cut by means of a rotating cutter having multiple cutting edges. For cutting operation, the workpiece is fed against the rotary cutter.
• As the workpiece moves against the cutting edges of milling cutter, metal is removed in form chips of trochoid shape. • Machined surface is formed in one or more passes of the
work.
• The work to be machined is held in a vice, a rotary table, a three jaw chuck, an index head, between centers, in a special fixture or bolted to machine table.
• The rotary speed of the cutting tool and the feed rate of the workpiece depend upon the type of material being machined.
(1) Plain milling cutters,
(2) Side milling cutters,
(3) Face milling cutter,
(4) Angle milling cutters,
(5) End milling cutter,
(7) T-slot milling cutter,
(8) Formed cutters,
(9) Metal slitting saw,
TYPES OF MILLING CUTTERS
TYPES OF MILLING CUTTERS
TYPES OF MILLING CUTTERS
Face milling cutter with inserted teeth Side milling cutter Plain metal-slitting saw cutter
TYPES OF MILLING CUTTERS
Angle milling cutter T-slot cutter
Up – Milling Method
Plain Milling Machining Parameters
Types of Milling Machines
The milling machines are available in different shapes and sizes. These machines may be classified as follows:
(1) Column and knee type milling machines (a) Horizontal milling machines
(b) Vertical milling machines (c) Ram type milling machines (2) Bed type milling machines
(a) Manufacturing or fixed bed type milling machines (b) Horizontal bed type milling machines
(c) Vertical bed type milling machines (3) Planer type milling machines
Plain horizontal milling machine.
Universal milling machine.
• The construction of a universal milling
machine is similar to that of the plain milling
machine, except that it is more accurate and
has a sturdier frame and its table can be
swiveled with an angle up to 50°.
• Universal milling machines are usually
equipped with an index or dividing head that
allows for the cutting of gears and cams.
Actual Universal milling machine.
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Bed Type Milling Machines
• Bed type milling machines are comparatively heavier
and rigid than column and knee type milling machines.
• In these machines, the table is mounted over a fixed
bed in the place of a knee.
• The spindle head imparts the cross or vertical motion
instead of a table. Depending on the number of spindle
heads provided in these machines, they can be ‘named
as simplex, duplex and triplex milling machines.
• Their types may be classified as horizontal or vertical,
based on the orientation of the spindle axis.
Schematic of Bed Type Milling Machines
Machining center
• A machining center is comprised of a multipurpose
CNC machine that is capable of performing a number
of different machining processes.
• A machining center has a tool magazine in which many
tools are held. Tool changes are automatically carried
out, and so are functions such as coolant turn-on/off.
• Machining centers are, therefore, highly versatile and
can perform a number of machining operations on a
workpiece with a single setup.
Universal dividing head
• The universal dividing head is an attachment mounted
on the worktable of a universal milling machine that is
employed for cutting gears.
• The function of the dividing head is to index the gear
blank through the desired angle each time the metal
between two successive teeth is removed.
• Therefore, this attachment is sometimes known as an
index head.
• A universal dividing head, which consists of the body,
the swivel block, the work spindle and its center, the
index plate, and the index crank with a latch pin.
Universal dividing head (contd..)
• The workpiece (with one of its ends supported by the
center of the work spindle) is rotated through the desired angle by rotating the index crank through an angle that is dependent upon the desired angle.
• The index crank is fixed to a shaft thatis, in turn, attached to a worm-gear reducer with a ratio of 40 to 1 .
• Consequently, 40 turns of the index crank result in only one full turn of the workpiece.
• This index plate has six concentric circles of equally spaced holes to assist in measuring and controlling any fraction of revolution in order to crank the correct angle.
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Operations performed on milling
machine
Operations performed on milling
machine (contd..)
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Operations performed on milling
machine (contd..)
Operations performed on milling
machine (contd..)
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