Milling Machine
Introduction:
Milling is the machining process in which the removal of metal takes place due to the cutting
action of a rotating milling cutter. In a milling machine, the cutter is rotating due to the
workpiece is fed against it. This machine can hold more than one tool at a time. The cutter
rotates at high speed, and because of the many cutting edges, it removes metal at a very fast
rate.
Universal Milling machine
The machine can also hold one or a number of cutters at a time. Thus, the milling machine is
one of the most important machines in the workshop. In this machine, all the operations can
perform with high accuracy.
The metal removal rate is high as compared to a lathe machine, planner machine, and shaper
machine. It has good accuracy and a better surface finish. This is why a milling machine finds
wide application in production work.
Working Principle of Milling Machine:
The working principle of the milling machine is applied in the metal-removing operation on a
milling machine. The work is rigidly clamped on the table of the machine and a revolving
multi-teeth cutter is mounted either on a spindle.
Working principle of Milling machine
The cutter revolves at a normal speed and the work fed slowly past the cutter. The work can
be fed in a longitudinal, vertical or cross direction. As the work progress further, the cutter
teeth remove the metal from the work surface to produce the desired shape.
Operations of Milling Machines:
Following are the different types of operations performed on milling machines:
1. Plain Milling Operation
2. Face Milling Operation
3. Side Milling Operation
4. Straddle Milling Operation
5. Angular Milling Operation
6. Gang Milling Operation
7. Form Milling Operation
8. Profile Milling Operation
9. End Milling Operation
10. Saw Milling Operation
11. Milling Keyways, Grooves, and Slot
Plain Milling:
✓ Plain milling is the most common type of milling machine operation.
✓ Plain milling is performed to produce a plain, flat, horizontal surface parallel to the
axis of rotation of a plain milling cutter.
✓ The operation is also known as slab milling.
✓ To perform the operation, the work and the cutter are secured properly on the
machine.
✓ The depth of cut is set by rotating the vertical feed screw of the table. And the
machine is started after selecting the right speed and feed.
Face Milling
✓ The face milling is the simplest milling machine operations.
✓ This operation is performed by a face milling cutter rotated about an axis
perpendicular to the work surface.
✓ The operation is carried in plain milling, and the cutter is mounted on a stub arbor to
design a flat surface.
✓ The depth of cut is adjusted by rotating the cross-feed screw of the table.
Side Milling
✓ The side milling is the operation of producing a flat vertical surface on the side of a
workpiece by using a side milling cutter.
✓ The depth of cut is set by rotating the vertical feed screw of the table.
Straddle Milling
✓ Straddle milling is the operation of producing a flat vertical surface on both
sides of a workpiece by using two side milling cutters mounted on the
same arbor.
✓ Distance between the two cutters is adjusted by using suitable spacing collars.
✓ The straddle milling is commonly used to design square or hexagonal surfaces.
Angular Milling
✓ Angular milling is the operation of producing an angular surface on a workpiece other
than at right angles of the axis of the milling machine spindle.
✓ The angular groove may be single or double angle and may be of varying included
angles according to the type and contour of the angular cutter used.
✓ One simple example of angular milling is the production of V-blocks.
Gang Milling
✓ Gang milling is the operation of machining several surfaces of a workpiece
simultaneously by feeding the table against a number of cutters having the same or
different diameters mounted on the arbor of the machine.
✓ The method saves much of machining time and is widely used in repetitive work.
✓ Cutting speed of a gang of cutters is calculated from the cutter of the largest diameter.
Form Milling
✓ Form milling is the operation of producing an irregular contour by using form cutters.
✓ The irregular shape may be convex, concave, or of any other shape. After machining,
the formed surface is inspected by a template gauge.
✓ Cutting rate for form milling is 20% to 30% less than that of plain milling.
Profile Milling
✓ Profile milling is the operation of reproduction of an outline of a template or complex
shape of a master dies on a workpiece.
✓ Different cutters are used for profile milling. An end mill is one of the widely used
milling cutters in profile milling work.
End Milling
✓ The end milling is the operation of producing a flat surface which may be vertical,
horizontal or at an angle in reference to the table surface.
✓ The cutter used is an end mill. The end milling cutters are also used for the production
of slots, grooves or keyways.
✓ A vertical milling machine is more suitable for end milling operation.
Saw Milling
✓ Saw-milling is the operation of producing narrow slots or grooves on a
workpiece by using a saw-milling cutter.
✓ The saw-milling also performed for complete parting-off operation.
✓ The cutter and the workpiece are set in a manner so that the cutter is directly
placed over one of the T-slots of the table.
Milling Keyways, Grooves, and Slots
✓ The operation of producing keyways, grooves, and slots of varying shapes and sizes
can be performed in a milling machine.
✓ It is done by using a plain milling cutter, a metal slitting saw, an end mill, or by a side
milling cutter.
✓ The open slots can be cut by a plain milling cutter, a metal slitting saw, or a side
milling cutter. The closed slots are produced by using endmills.
T-slot-operation
✓ A dovetail slot or T-slot is manufactured by using special types of cutters designed to
give the required shape on the workpiece.
✓ The second slot is cut at right angles to the first slot by feeding the work past the
cutter.
✓ A woodruff key is designed by using a woodruff key slot cutter.
✓ Standard keyways are cut on the shaft by using side milling cutters or end mills.
✓ The cutter is set exactly at the centre line of the workpiece and then the cut is taken.
Gear Cutting
✓ The gear cutting operation is performed in a milling machine by using a form-relieved
cutter. The cutter may be a cylindrical type or end mill type.
✓ The cutter profile fits exactly with the tooth space of the gear.
✓ Equally spaced gear teeth are cut on a gear blank by holding the work on a universal
diving head and then indexing it.
