Mechanical Engineering

Milling Machine

Milling Machine

• Used to produce one or more machined surfaces accurately on work piece– One or more rotary milling cutters

• Work piece held on work table or holding device and brought into contact with cutter.

Vertical Milling Machine

Horizontal Milling Machine

Operation done

• Face milling• End milling• Keyway cutting• Dovetail cutting• T-slot and circular

slot cutting

• Gear cutting• Drilling• Boring• Jig boring

Factors in Determining Cutting Speed

• Type of work material• Cutter material• Diameter of cutter• Surface finish required• Depth of cut taken• Rigidity of machine and work setup

Factors in Feed Rate

1. Depth and width of cut2. Design or type of cutter3. Sharpness of cutter4. Workpiece material5. Strength and uniformity of workpiece6. Type of finish and accuracy required7. Power and rigidity of machine, holding

device and tooling setup

Direction of Feed/ milling process(up cut milling)

Up Cut Milling

Down Cut Milling

Conventional Milling (Up cut)• The width of the chip starts from zero and

increases as the cutter finishes slicing.• Upward forces are created that tend to lift the

workpiece during face milling.• More power is required to conventional mill

than climb mill.• Surface finish is worse because chips are

carried upward by teeth and dropped in front of cutter.

Conventional Milling( Up cut)

• Tools wear faster than with climb milling.• Conventional milling is preferred for rough

surfaces.

Climb milling (Down cut)

• The width of the chip starts at maximum and decreases.

• Chips are dropped behind the cutter--less recutting.

• Less wear, with tools lasting up to 50% longer.• Improved surface finish because of less

recutting.• Less power required.

Climb milling (Down Cut)

• Climb milling exerts a down force during face milling, which makes workholding and fixtures simpler.

• Climb milling reduces work hardening.

Cutting Tools

Slab Mill Side and Face Cutter Slitting Saw

End Mill Rough Cut End Mill Slot Drill

Milling operation

Method of holding work

• 1. Milling machine Vice• Small components are usually held in a

machine vice which is itself bolted to the machine table.

Swivel Base and Vise

Plain Milling Machine Vise

Universal Angle Milling Vise

Clamp to the milling machine table

• Large components such as castings are supported directly on the machine table. Care must be taken when tighten the clamps to avoid distorting the work piece. Jacks and wedges should be used to ensure adequate support unless a previously machined datum surface is available.

Dividing Head• This device is used when it is necessary to mill

slots round the periphery of a circular blank. For example: keyways, splines, gear teeth.

Simple indexing

• A method use when making series of cuts around the periphery of a component; for example when cutting gears.

Index plate

Calculation

• Simple indexing = 40/N• Where N= the number of divisions required

• Example : calculate the simple indexing to give 13 equally spaced divisions. The index plate has the following number of holes: 24, 25, 28, 30, 34, 37, 38, 39, 41, 42, 43.

Solution

• Simple indexing= 40/N• =40/13• = 3 1/13• Answer 3 whole turns and 3 holes in the 39-

hole circle.•

Question

• Using the same index plate as in the previous example, calculate the following division:

• A. 26• B. 39