Milling Machine Operations

A large variety of components can be machined on a milling machine which involves various types of operations. These operations are broadly classified as follows.

Plain or slab milling,

Face milling,
Angular milling,
Straddle milling,
Slot and groove milling,
Slitting or saw milling,
End milling,
Gear milling,
Form milling,
Gang milling,
Keyway milling,
Side milling,
Profile milling,
Thread milling

1. Plain or slab milling

Plain milling is used for machining a flat, plain, horizontal surface, parallel to the axis of cutter with the help of plain or slab milling cutter. For machining of very wide surface, interlocking teeth plain milling cutters are used instead of simple plain milling cutters. During the operation, the work piece and cutter ate secured properly on the machine and by rotating the vertical feed screw of the table and machine, the depth of cut is adjusted.

Plain or slab milling

2. Face milling

Face milling is employed for machining a flat surface which is at right angle, to the axis of revolving cutter. The cutter used in the process is face milling type which is rotated about an axis Perpendicular to the work piece. The operation is performed on plain milling machine and depth of cut is adjusted by rotating the cross feed screw of the table. Face mills under 150 mm are called as shell mills and are held on a short arbor.

Face milling

3. Angular milling

Angular milling is used for machining a flat surface at an angle, other than right angle, to the axis of milling machine spindle. For example, V-blocks. According to the type of surface (single or two mutually inclined), the single or double angle cutters may be used.

Angular milling

4. Form milling

Form milling is the operation of machining irregular contours by means of form milling cutter. The irregular contour may be concave, convex or of any other shape. The cutting speed of form milling process is 20 - 30 % less than that of the plain milling.

Form milling

5. Straddle milling

Straddle milling is the operation of flat vertical surfaces on both the sides of a work piece simultaneously. For this purpose two side milling cutters are mounted on the same arbor. By using suitable spacing collars, the distance between the two cutters can be adjusted. This process is mainly used for production of square and hexagonal surfaces.

Straddle milling

6. Gang milling

Gang milling is the operation of machining several surfaces of the work piece simultaneously. For this, table is fed against the number of cutters having same or different diameters mounted on a common arbor. This method saves machining time and is widely used in repetitive work.

Gang milling

7. Slot and groove milling

slot milling is the operation of producing slots in solid work pieces.These slots can be of different shapes such as plain slots, T-slots, dovetail slots etc. Plain slot can be milled by using plain milling cutter and end milling cutter. Groove milling is the operation of producing grooves of various shapes like plain grooves, curved grooves, v grooves, etc. According to the shape of slot or groove, the cutter is selected. These operations are carried out in two or three stages. In first stage, open slot is milled by using suitable cutter (plain milling cutter) and then the slot is milled by using special cutters like T-slot milling cutter.

Milling a plain slot by end milling cutter

8. Keyway milling

Keyway milling

Keyway milling is a common operationwhich is performed on milling machine In this a groove is milled on shafts and spindles, which is known as key seat. Fig. shows different types of key seats. awoodruff key seat which is milled with woodruff key seat cutter. Sunk key seat which is milled with end milling cutter.

9. Slitting or saw milling

Saw milling is the operation of production of narrow slots or grooves on a work piece by using a saw or slitting milling cutter. It is also used for complete parting-off operation. The cutter and work piece are set in such a way that, the cutter is directly placed over one of the T-slots of the table.

Slitting or saw milling

10. Side milling

In this operation a side milling cutter is used for machining a flat vertical surface on one side of the work piece. When two parallel vertical flat surfaces are required to be machined, then two side milling cutters in pairs are used. By using spacer, the space between two cutters can be adjusted. Hence, this operation is similar to straddle milling.

side milling

11. End milling

This operation is used to machine and produce a flat surface or a pair of flat surfaces by using an end milling cutter. Fig. shows the end milling operation in which flat surface is produced withthe help of an end milling cutter. The surfaces produced may be horizontal, vertical or inclined with respect to the top of the machine table.

End milling

12. Profile milling

In profile milling, the profile of a template or cavity shape of a master-die is duplicated on the work piece surface. The cutter movement is guided by a tracer control unit which carries a contact finger. This finger runs in contact with the outline to be duplicated and the tracer mechanism guides the tool accordingly.

profile milling

13. Gear milling

Spur gears are easily produced on plain and universal milling machines for cutting helical, worm and bevel gears dividing heads are required. (Discussed later in this chapter). Fig shows that, the cutter is mounted on arbor with its axis at right angle to the work piece. Cutter is properly adjusted so that its central line is radial with the blank. The knee is raised to adjust the required depth of teeth. In a single pass, one tooth is finished and table is returned to its starting position.

Gear milling

14. Thread milling

Thread milling is a method of cutting screw threads with the help of form-milling cutters. Both internal and external threads can be milled. Thread milling is associated with single or multiple cutters. A single form cutter has a single row of annular teeth which are lying in one plane. While cutting, a cutter is tilted through a helix angle of the thread to avoid interference during cutting. During the process, the cutter is fed radially inward up to the required depth of thread and work piece remains stationary. The work piece is held between centers of the machine. Now, the job is rotated slowly and cutter while rotating is also traversed longitudinally parallel to the work piece axis with the help of lead screw. Thread milling is used for cutting coarse threads as shown in Fig.. Thread milling with multiple teeth cutter (hob) is as shown in Fig. The process is almost similar to milling with single cutter. But, the width of the cutter is slightly more than length of thread produced on the work piece.

Thread milling