Chapter4 - MILLING PROCESS

FIG. 1 Typical parts and shapes produced by various cutting processes

Fig. 2 Schematic illustration of milling machines

Fig. 3 Milling machines

Fig 4 Nomenclature of a common milling cutter

Left hand spiral right hand spiral

Left hand cutter right hand cutter

Fig. 5 Left and right hand cutters.

Helical Plain

Fig. 6 Milling Cutters. a ) Helical b ) Plain

Slab mill Course tooth millHelical mill

Staggered tooth mill Side mill Interloching mill Metal slitting saw

Fig. 7 Various types of milling cutters

Helical mill (arbor type)

Fig. 8 Various types of end mills

Woodruff Keyslot end millDouble-end end mill

Two-lip end mill

Shell end millT-slot end mill

Fig. 9 Angle, concave, convex, corner and gear cutters

Corner rounding cutter Covex formed cutter Gear tooth cutter

Single angle cutter Double angle cutter Concave formed cutter

Fig. 10 Effect of milling cutter diameter on workpiece travel

Large diameter cutter

Amount of travel using large diameter cutter

Direction of cut

Material being removed

workpieceSmall diameter cutter

Amount of travel using small diameter cutter

Fig.11 Tapers used for Milling machine arborrs

Fig. 12The standard milling machine arbor

Arbor

Intermediate arbor support Arbor support

Spindle

Draw in boltMilling cutter Journal bearing Arbor nut

Fig. 13 Arbor installation

Fig. 14 Typical milling arbors

Fig. 15 Typical Collet types

Milling machine adapters Chuck adapter

Fig. 16 Adapters

Fig. 17 Quick change adapter and tool holder.

Fig. 18 examples of various vises

swivel viseStandard machine table vise

The universal vise

Fig. 19 The index head and footstock

Fig. 20 Rotary table

Fig. 21 Offset boring head

Angle plate V-Block and clamp V-clamp C- clamp

Step block Bent tail machine clamp Finger machine clamp Strap clamp C- clamp

Fig.22 Various mounting tools

Not correct CorrectWorkpiece

Parallel ParallelSelection of Parallels

Vise

Workpiece Workpiece

Centering of workpiece in vise

Locating the workpiece at end of vise

Fig. 24 correct mounting of workpiece in a vise

Strap block

WorkpieceWorkpiece

Vise

Vise

Fig. 23 locating keys or tongues on the underside of the vise bases should be located correctly in relation to the T-slots on the milling machine table vise.

Fig. 25 using hold down straps

Fig. 26 The indexing plate

Brown and Sharpe type Plate I - 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

Cincinnati type 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

a) Slab milling b) Face milling c) End milling

Arbor

Arbor

Cutter

Spindle

Spindle

Shank End mill

Fig. 27 Examples of Milling Cutters and Operations

d) e)

Fig. 28 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.

Fig. 29 (a) Slab milling operation, showing depth of cut, d, feed per tooth, f, chip depth of cut, tc, and workpiece speed, v. (b) Schematic illustration of cutter travel distance lc to reach full depth of cut.

f v

v

(a) (b)

TABLE 1 Typical capacities and maximum workpiece dimensions for milling machines

Machine tool Maximum dimension

m (ft)

Power (kW)

Maximum speed

Milling machines (table travel)

Knee-and-column

1.4 (4.6) 20 4000 rpm

Bed 4.3 (14)

Numerical control

5 (16.5)

Note: Larger capacities are available for special applications.

TABLE 1 Parameters and formulae of the milling process

N= Rotational speed of the milling cutter, rpm

f = Feed, mm/tooth or in./tooth

D = Cutter diameter, mm or in.

n = Number of teeth on cutter

v=

Linear speed of the workpiece or feed rate, mm/min or in./min

V = Surface speed of cutter, m/min or ft/min

=D N

f = Feed per tooth, mm/tooth or in/tooth

=v /N n

l = Length of cut, mm or in.

t = Cutting time, s or min

=( l+lc ) v , where lc =extent of the cutter’s first contact with

workpiece

MRR = mm3/min or in.3/min

=w d v , where w is the width of cut

Torque = N-m or lb-ft

( Fc ) (D/2)

Power = kW or hp

= (Torque) ( ), where = 2 N radians/min

Note: The units given are those that are commonly used; however, appropriate units must be used in the formulas.

Fig. 31 A typical setup for plain milling

Fig. 32 is a typical example of angular milling.

Fig. 33 Straddel milling of a hexagon

Fig. 34 Face milling

Fig. 35 Face milling of angular surfaces

Fig. 36 Gange milling. Fig. 37 Form milling

Fig. 38 Fly cutting tools

Fig. 39 The Woodruff key slot milling cutter

Key is milled to required length

Cutter centered over the shaft

Fig. 40 Milling rounded end key slot waysKey is milled to required length

Fig. 41 T-slot milling cutter

Fig. 42 Parting of a solid stock

Fig. 43 The splines are cut by straddle milling