What are the Work Holding Devices Used on Milling Machine?

It is necessary that the work should be properly and securely held on the milling machine table for effective machining operations. The cutting pressure exhorted by milling cutter is quite high comparing the single point tool of lathe machine. Therefore the work piece has to be secured rigidly to avoid any vibration. The following are the usual methods of holding work on the milling machine.

Types of work holding devices

Various types of work holding devices are explained in the following paragraphs.

T- Bolts and clamps - Bulky work pieces of irregular shapes are clamped directly on the milling machine table by using T- bolts and clamps. Different types of clamps are used for different patterns of work. The common types of clamps are shown in Fig 10 of chapter 5. All these clamps carry a long hole, through which clamping bolt passes. This hole permits the bolts for adjustment according to the size and shape of the job.

Angle plates - When work surfaces are to be milled at right angles to another face, angle plates are used for supporting the work.

V block - The V blocks are used for holding shafts on milling machine table in which keyways and slots are to be milled.

Vices - Vices are most common appliance for holding work on milling machine table. According to its quick loading and unloading arrangement. Vices are of three types,

(a) Plain Vice - The plain vice is directly bolted on the milling machine table is the most common type of vice used on plain milling operations, which involves heavy cuts, such as in slab milling. Its especially low construction enables the work to remain quite close to the table. This reduces the chance of vibration to minimum. The base carries slots to accommodate ‘T’ bolts to fix the vice on the table. Work is clamped between the fixed and movable jaw and for holding work pieces of irregular shape special jaws are sometimes used.

(b) Swivel Vices - The swivel vice is used to mill an angular surface in relation to a straight surface without removing the work from the vice. It has got circular base graduated in degrees. The base is clamped on the table by means of T- bolts.

(c) Universal Vices - It can be swiveled in a horizontal plane similar to a swivel vice and can also be tilted in any vertical position for angular cut. The vice is not rigid in construction and is used mainly in tool room work. It enables the milling of various surfaces, at an inclination to one another, without removing   the   work   piece.

Dividing Head - Dividing head or indexing head used to hold the work piece and divide the periphery into the number of divisions required. These are of three types:

(a) Plain dividing head

(b) Universal dividing head

(c) Optical dividing head

Work directly mounted on table or Special fixtures

Work directly mounted on the table for heavy nature of jobs or odd shaped jobs which is not possible to hold by other holding devices, with the help of slots, T- bolts and nuts. The fixtures are special devices designed to hold work for specific operations more efficiently than standard work holding devices. The fixtures are especially useful when large numbers of identical parts are to be manufactured.