Milling Machine: Attachments and Accessories | Industrial Engineering

In this article we will discuss about:- 1. Attachments for Milling Machine 2. Special Accessories for the Universal Milling and Boring Machine.

Attachments for Milling Machine:

The various attachments are described below and also how they increase the versatility of the milling machine.

1. Vertical Milling Attachment or Swivel Attachment:

This attachment is desirable on horizontal milling machines for substituting the horizontal spindle by a vertical spindle motion. The attachment is a right-angle gear box having bevel gear set in ratio of 1 : 1 and the axis of the vertical spindle could also be swivelled by 45°, thus allowing the machining of bevels and slanted surfaces.

With the help of this attachment, the operation of milling horizontal surfaces and making grooves and slots with shank type end mills etc. can also be carried out on horizontal milling machine. The attachment is fitted to the column of the machine with four bolts.

2. High-Speed Milling Attachment:

With the help of this attachment the speed of the spindle can be increased three to four times so that the operation with small cutters could be carried out efficiently. The attachment is mounted on the column with four bolts and can be swivelled also at any angle.

3. Slotting Attachment:

With the help of this attachment, square holes, slots and a variety of jobs can be made on milling machine which a rotary tool can’t do. This unit is mounted on the column face and converts rotary motion into reciprocating motion. The usual range of linear movement is 0-10 cm with an adjustment for 360 degrees swivel. This attachment allows the machining of keyways, slots and certain grooves.

4. Universal Dividing Head (Index Head):

This attachment is very essential for a milling machine. It is used for cutting gear teeth, slots or grooves on the periphery of the work. With its help the job can be rotated by exact degrees and by various methods of indexing (direct, simple or compound), nearly any number of exact slots or teeth can be cut.

The indexing may be done by hand or automatically. For automatic rotation of job, the correlation of rotation with feed table is worked out, and gearing arrangement is provided at the end of index head which may be connected to the table driving mechanism. Thus continuous motion for indexing of the work can be obtained.

This power drive is very useful for milling such work-pieces as twist-drill flutes, helical gears, spiral milling cutters and many other pieces having a helix or similar geometric form.

5. Circular Milling Attachment:

This is a sort of rotary table provided with T-slots. Its circumference is divided into degrees and may be hand-indexed for spacing or locating slots, grooves, or holes. For the purpose of milling a circular arc or groove on the job, an arrangement can be used to make it power-operated to provide continuous motion.

Index plates can also be fitted to this attachment for obtaining exact rotation of the job by any fraction of a circle. With the help of this attachment, may profiles can be produced, such as straight or curved slots, grooves, cams and rounded ends on workpiece.

6. Rack Milling Attachment:

It is used for milling straight or inclined racks or cross-slotted pieces of large lengths on horizontal or universal milling machine. It consists of a milling unit, a fixture and a rack indexing unit. The milling unit is mounted on the column face and is supported at the front by an overarm. It has a spindle having its horizontal axis at right angles to that of the machine.

7. Vise:

This is also a very essential attachment and is bolted to the top of the table. It can be fastened to the table in any position by fastening the T-bolt on the ears at the end of the vise. It is generally used as dead centre to support the job.

It holds the work-pieces securely and helps in orienting it accurately. Work-piece is held between two hardened and ground jaws. Vises are of three types viz., (a) plain (b) swivel (Refer Fig. 16.23) tool-maker universal (Refer Fig. 16.24).

Milling machine vises are usually specified according to the jaw lengths. The standard metric sizes are 125, 160, 200 and 250 mm.

The plain vise can be bolted to the table either parallel or perpendicular to the machine spindle. The swivel vise can be swivelled in a horizontal plane and can be used for holding work to be cut at angle.

The universal vise can be swivelled in a horizontal plane and can also be hinged up away from the plane of the table for an angle of 0 to 90 degrees, thus making it possible to adjust the job in any way Compound angled surfaces can be milled with this type of arrangement. However, the size of the work that can be held by the vise is limited.

Various positioning devices shown in Fig. 16.25 can be adopted to most machine tools.

8. Arbors:

Arbors are used to hold milling cutter on milling machines. All peripheral milling cutters, shell end mills, etc., are mounted on arbors and held in the spindle through a draw bolt arrangement (Refer Fig. 16.26). The cutter is driven through a key fitted on the arbor. One or more arbor supports may be provided to ensure added rigidity.

Arbors can be either long or stub. Small shell end mills and face mills and side and face cutters are mounted on the front end of stub arbors. The stub arbor is held in the spindle through a draw bolt arrangement, but the arbor being short is not supported at its free end.

It is possible to mount a milling cutter directly on the spindle or on arbors, adaptors or collets held in the spindle nose. Large shell end mills and face mills are directly mounted on spindle spigots centered on the outside and clamped on the spindle face.

Other attachments include universal head milling attachment, rack milling attachment, thread milling attachment, precision measuring instruments and micrometer stops.

Special Accessories for the Universal Milling and Boring Machine (Fig. 16.27):

i. Hydraulic Clamping Vice (Fig. 16.27 (a)):

Accurate, and easily adjustable vice. Simple and rapid operation by hydraulic action. The clamping pressure can be adjusted and controlled. Mechanical coarse adjustment and hydraulic clamping operation.

ii. Mechanically Operated High Pressure Clamping Vice (Fig. 16.27 (b)):

Robust and strong design. Head and clamping slide can be shifted and positioned on the lower slide section by means of adjustable pins. Basic slides of different lengths can be used and combined to give a double acting vice.

iii. Universal Precision Vice (Fig. 16.27 (c)):

Special, fine grained, gray cast iron.

Swivelling of the vice on its cradle through 360^o.

Swivelling of the cradle on the base plate through 360^o.

Inclination of the vice surface: 90^o in one direction, 30^o in the other direction.

iv. Semi-Universal Indexing Device (Fig. 16.27 (d)):

Semi-universal indexing device for direct or indirect indexing as well as indexing by degrees on a scale. The workpiece can be clamped between centres, collets or three jaw chucks. Completely enclosed design.

v. Helical Milling Device (Fig. 16.27 (e)):

This device combined with the vertical milling head and the spindle slide permits the manufacture of pieces with helical gashes (limited conical form). It is mounted on the fixed table and consists of a universal indexing device which enables direct, indirect and differential indexing. The tailstock of the indexing device can be adjusted in its height and angularity.

vi. Vertical Indexing Device (Fig. 16.27 (f)):

With overarm and swivel angle plate to be directly fixed in the vertical position on the vertical table slide of the milling machine. It is used for direct or indirect indexing and indexing by degrees on a scale. The workpiece can be clamped between centres, three- jaw chucks, face plates or collets.

vii. Punch Milling Attachment (Fig. 16.27 (g)):

An important economic attachment for tool manufacture. It enables a considerably simpler, quicker and more accurate work like, manufacture of blanking punches, extended range of application with broaching device (keyways, conic milling device, etc.).

viii. Rotary Table (Fig. 16.27 (h)):

For indexing by degrees on a scale and indirect indexing. Fast change-over from one system to the other (3 indexing disks) by tightening or releasing a ring nut. High accuracy. (Indexing accuracy 30 seconds).

ix. Centering Microscope (Fig. 16.27 (i)):

With built-in illumination, magnification 20 x, with case. Eyepiece angle 70°. Focal length approx. 30 mm. Built-in graticule, with cross wires and 12 concentric circles, with fine adjustment from all sides. Shock and tamper proof eyepiece.

x. Precision High Speed Spindle (Fig. 16.27 (j)):

Built of special steel hardened and ground, mounted on ball bearings, quiet and free from vibrations, increases the speed range.

xi. Adjustable Multi-Angle Milling Head (Fig. 16.27 (k)):

The adjustable multi-angle milling head is especially suitable for the accurate machining of internal angles and inner edges of workpiece parts which are not easily accessible.

The milling head is adjustable from 0° to 90°. It can be swivelled through 360^o inside its axial fitting housing according to a graduated scale and axially shifted by 60 mm. This adjustability permits facing, chamfer milling, notching and grooving of any angle within 0° and 90^o.

Thus several operations can be carried out in one set-up only, by means of which considerable saving of idle and operating times are achieved. All the parts subject to heavy loading e.g. spindles and bevel gears are hardened and ground.

xii. Right-Angle Milling Head (Fig. 16.27 (l)):

This head can be swivelled through 360° inside its axial fitting housing according to the same graduated scale and shifted by 60 mm. The right angle milling head is specially suited for producing keyways, oil grooves and internal pockets.

This accessory eliminates expensive set-up times and alignment problems as multiple operations are carried out in one set-up only. All the parts subject to heavy loading e.g. spindles and bevel gears are hardened and ground.

xiii. Measuring and Centering Instrument (Fig. 16.27 (m)):

Indispensable for the centering of workpiece angles and bores as well as for the checking of concentricity and parallelism. Dial indicator can pivot through 360^o for accurate reading with the instrument in any position (internal, external and plane).

xiv. Universal Cross-Slide Milling Head (Fig. 16.27 (n)):

This head was developed as an auxiliary attachment for milling machines. The design presents a most versatile range of possible applications.

Economic production of complicated parts is made possible by the cross slide and rotary motion features of this milling head.

The rotary motion is actuated either manually or mechanically by worm gear drives.

The milling head can be fitted rapidly on the quill of the machine spindle by means of an adapter flange.

xv. Tool Cabinet:

The steel tool cabinet is suitable for the careful storage of tools and accessories. The cabinet is provided with four ball bearing drawers of which two are equipped as simple drawers and two as double drawers which in turn can be fitted out with different inserts.