2. INTRODUCTION
• Milling is a basic machining process by which a
surface is generated by progressive chip removal.
• The w/p is fed into a rotating cutting tool.
Sometimes the w/p remains stationary, and the
cutter is fed into the work.
• A multi-point cutting tool is used in milling
operation, which is known as milling cutter.
3. THE PROCESS
• The milling process:
▫ Typically uses a multi-tooth
cutter
▫ Work is fed into the
rotating cutter
▫ Capable of high MRR
▫ Well suited for mass
production applications
▫ Cutting tools for this
process are called milling
cutters
4. CLASSIFICATIONS
• Milling operations are classified into two major
categories:
▫ Peripheral (side)
Generally in a plane parallel to the axis of the cutter
Cross section of the milled surface corresponds to
the contour of the cutter
▫ Face
Generally at right angles to the axis of rotation of the
cutter
Milled surface is flat and has no relationship to the
contour of the cutter
Combined cutting action of the side and face of the
milling cutter
5. MILLING PROCESS
Some basic types of milling cutters and milling operations. (a) Peripheral milling.
(b) Face milling. (c) End milling. (d) Ball-end mill with indexable coated-carbide
inserts machining a cavity in a die block. (e) Milling a sculptured surface with an
end mill, using a five-axis numerical control machine.
6. RELATED OPERATIONS
▫ Side milling - machining a plane surface
perpendicular to the milling machine arbor with
an arbor mounted tool. This tool is called a side
mill.
▫ Straddle milling - milling two parallel surfaces
using two cutters spaced apart on an arbor.
▫ Gang milling - milling multiple surface
simultaneously using multiple cutters mounted on
an arbor.
9. MILLING MACHINES
• Two Major Classifications - Knee & Column and Bed
▫ Knee & Column (Bridgeport type)
Basic job shop type mill
Column mounted to the base which is the major support frame.
Construction provides controlled motion of the worktable in three
mutual perpendicular directions.
Knee moves vertically on the ways in the front of the machine
Table moves longitudinally on the ways on the saddle
Saddle moves transversely on the ways on the knee
Quill moves parallel in Z axis or, if head is rotated, X axis
Versatile general purpose machine
10. Column-and-Knee Type Milling Machines
Schematic illustration of (a) a horizontal-spindle column-and-knee type milling
machine and (b) vertical-spindle column-and-knee type milling machine.
11. MILLING MACHINES
▫ Bed
Used extensively in production milling operations
Rigid construction capable of heavy cuts
Table is mounted directly to the bed
Spindle head moves vertically to set depth of cut
Head locks into position for cut
Base of machine functions as a coolant reservoir
12. BED TYPE MILLING MACHINE
Fig : Schematic illustration of a bed-type milling machine. Note the single vertical-spindle cutter
and two horizontal-spindle cutters.
15. Five-Axis Profile Milling Machine
Schematic illustration of a five-axis profile milling machine. Note that there are
three principal linear and two angular movements of machine components.
18. MILLING CUTTERS
• Milling cutters can be classified according to the
way the cutter is mounted in the machine tool:
▫ Arbor cutters
▫ Shank cutters
• Another method of classification applies only to
face and end mill cutters and relates to the
direction of rotation:
▫ Right hand cutter
▫ Left hand cutter
24. Milling Operations
(a) Schematic illustration of conventional milling and climb milling. (b) slab-
milling operation showing depth-of-cut, d; feed per tooth, f; chip depth-of-cut, tc;
and workpiece speed, v. (c) Schematic illustration of cutter travel distance, lc, to
reach full depth-of-cut.
25. Face-Milling Operation
Face-milling operation showing (a) action of an insert in face milling; (b) climb
milling; (c) conventional milling; (d) dimensions in face milling. The width of cut,
w, is not necessarily the same as the cutter radius.
26. WORKHOLDING DEVICES
• Vise
• Chucks
• Rotating tables
• Angle plates
• Special fixtures
• Universal dividing head
• Modular fixturing systems
• Clamp work to table
29. STANDARD DIVIDING HEAD
• A dividing head is a tool that is used to divide a
circle into equal divisions.
30. STANDARD DIVIDING HEAD
• In a nut shell, a dividing head is simply a spindle mounted with a precision
worm wheel and provided with a crank attached to the worm shaft.
• The crank's handle is equipped with a spring loaded plunger that will drop
an indexing pin into equally spaced holes in a disk mounted behind the
crank.
• The spindle is provided with the means to mount a chuck or collet
attachment for holding a workpiece.
• It is also provided with a lock for clamping the spindle in position for
increased rigidity.
• These units are usually mounted such that the spindle's axis can be tilted
through 90 degrees, to provide an additional axis of adjustment.
• Most units are made with a 40:1 reduction in the worm, such that 40 turns
of the crank will rotate the spindle through one full turn.
31. • The indexing plate is a disk with concentric circles of equally spaced holes
situated behind the crank.
• It provides a handy positive index for positioning the crank at 1/n turns of the
crank, where n equals the number of holes in the disk.
• The plunger can be positioned along the arm of the crank to select which circle
of holes you wish the indexing pin to engage.
• These indexing plates are usually interchangeable to provide a wide variety of
choices for n, so that one turn of the spindle can be divided into a great variety of
equal parts.
• The crank is outfitted with a pair of sector arms which can be adjusted to
indicate the correct number of holes for any partial turn of the crank you must
make.
• This eliminates the need to count holes on every subsequent advance of the
spindle.
INDEXING PLATE
33. PROCEDURE
• Dividing a circle into 40 equal parts is pretty straight forward since the
worm wheel has 40 teeth - one full turn of the crank equals one fortieth
of a circle at the spindle.
• To divide a circle into 20 parts: two turns of the crank would equal two
40ths, or one 20th of a circle.
• One fourth of a crank turn (or 6 holes in a 24 hole index circle) would
equal one 160th of a circle at the spindle.
• Here is the formula:
crank turns = 40 / N
where N = the desired number of equal divisions at the spindle
• Reduce this fraction to its simplest form. Use any whole number to
represent complete turns, and use the denominator to determine the
index plate to use.
34. Generally two types of Index Plates are supplied:
1. Brown and Sharpe type, 3 plates of 6 circles, each drilled as follows:
Plate 1- 15, 16, 17, 18, 19, 20 holes.
Plate 2- 21, 23, 27, 29, 31, 33 holes.
Plate 3- 37, 39, 41, 43, 47, 49 holes.
2. Cincinnati type, one plate drilled on both sides with circles divided as
follows:
First side- 24, 25, 28, 30, 34, 37, 38, 39, 41, 42, 43 holes.
Second side- 46, 47, 49, 51,53, 54, 57, 58, 59, 62, 66 holes.
PROCEDURE
35. PROCEDURE
Example 1: T0 divide a circle in 6 equal parts:
• Using the rule given above, divide 40 by 6, which equals 6 2/3 turns, or six
full turns plus 2/3 of a turn on any circle whose number of holes is divisible
by 3.
• Therefore, six full turns of the crank plus 12 spaces on an 18-hole circle, or
six full turns plus 26 spaces on a 39-hole circle will produce the desired
rotation of the workpiece.
Example 2: To Cut a Gear of 42 Teeth:
• Using the rule again, divide 40 by 42 which equals 40/42 or 20/21 turns, 40
spaces on a 42-hole circle or 20 spaces on a 21-hole circle.
• To use the rule given, select a circle having a number of holes divisible by
the required fraction of a turn reduced to its lowest terms. The number of
spaces between the holes gives the desired fractional part of the whole
• Indexing
