Work holding Devices of Milling, Shaping, Planing

& Slotting Machines

Done by

R. MUKHIL14M439

Work Holding Device

Work holding refers to any device that is used to a secure a workpiece and hold it in place against the forces of machining. The most basic work holding device is a simple clamp that is screwed into place on a machining center’s table, but work holding can also involve complex fixtures that are custom-built for particular parts. Other common work holding devices include vises and chucks, as well as indexers or rotary tables that are able to change the part’s position while it is held, so the machine can reach various features of the part without the setup having to be changed. In most machining applications, work holding also locates the part. In turning, for example, a chuck not only holds the part securely but also holds it precisely on the centreline of the spindle. On a machining center, the vise or fixture that holds the part may also hold it in the precise position and orientation where the machining program expects to find it. For this reason, components such as locating pins and workstops that make it easy to place piece after piece in the same location are also common work holding components.

Work Holding Devices of Milling Machines

Tool Maker Universal Vise

The universal vise can be swivelled in a horizontal plane similar to a swivel vise and can also be tilted in any vertical position for angular cuts. The rise not being rigid in construction is used mainly in tool room work.

Plain Vise

 Either a plain or swivel-type vise is furnished with each milling machine. The plain vise, similar to the machine table vise, is used for milling straight workplaces and is bolted to the milling machine table either at right angles or parallel to the machine arbor.

Swivel Base Vise

V-Block

V-Blocks are precision metalworking jigs typically used to hold round metal rods or pipes for performing drilling or milling operations. They consist of a rectangular steel or cast iron block with a 90-degree channel rotated 45-degrees from the sides, forming a V-shaped channel in the top. A small groove is cut in the bottom of the "V". They often come with screw clamps to hold the work. There are also versions with internal magnets for magnetic work holding. V-blocks are usually sold in pairs.

Dividing Head

An indexing head, also known as a dividing head or spiral head, is a specialised tool that allows a workpiece to be circularly indexed; that is, easily and precisely rotated to preset angles or circular divisions. Indexing heads are usually used on the tables of milling machines, but may be used on many other machine tools including drill presses, grinders, and boring machines. Common jobs for a dividing head include machining the flutes of a milling cutter, cutting the teeth of a gear, milling curved slots, or drilling a bolt hole circle around the circumference of a part.

Rotary Table

A rotary table is a precision work positioning device used in metalworking. It enables the operator to drill or cut work at exact intervals around a fixed (usually horizontal or vertical) axis. Some rotary tables allow the use of index plates for indexing operations, and some can also be fitted with dividing plates that enable regular work positioning at divisions for which indexing plates are not available. A rotary fixture used in this fashion is more appropriately called a dividing head (indexing head).

Tilting Table

Angle Plate

When working surfaces are to be milled at right angles to another face, angle plates are used for supporting the work. The angle plate bolted on the table and the work piece is supported on its face by bolts and clamps.

T-Bolts & Clamps

Bulky work pieces of irregular shapes are clapped directly on the milling machine table by using T-Bolts and Clamps

Work Holding Devices of Shaping Machine

Shaper Vise

Vise is a quick method of holding and locating relatively small and regular shaped work pieces.

Parallels

When the height of the job is less than the height of the jaws of the vise,

parallels are used to rise and seat the workpiece above the vise jaws and

parallel with the vise.

Hold Downs

Hold downs are grippers are used for holding thin pieces of work in a shaper vise.

Clamping work on the Table

The different methods employed to clamp different types of work on a shaper table are:

T- Bolts and Clamps

Stop Pins: A stop pin is a one-leg screw clamp. Stop pins are used to prevent

the work from coming out of the position.

Stop Pins & Toe Dogs

While holding thin work on the table, stop pins in conjunction with toe dogs are used.

Strip and Stop Pins: Work having sufficient thickness is held on the table by strip and stop pins.

Angle Plate

V-Block

Shaper Centres

This is a special attachment used for cutting equally spaced grooves or splines on the periphery of a round work.

Work Holding Devices of a Planing Machine

The work may be held on a planing machine table by the following methods:

1. By Standard Clamping

2. By Special Fixtures

Standard Clamping Devices: The standard clamping devices are used

for holding most of the work on a planner table. The devices are as follows:

1. Heavy Duty Vises

2. T-Bolts and Clamps

3. Stepblocks, Clamps and T-Bolts

4. Poppets or Stop pins and Toe dogs

5. Angle plates

6. Planer jacks

7. Planer centres

8. Stops

9. V-Blocks

Special Fixtures

Special fixtures are used for holding a large identical pieces of work on a planer table. Fixtures are specially designed for holding a particular type of a work. By using a fixture the setting time may be reduced considerably.

Work Holding Devices of a Slotting Machine

The work is held on a slotter table by a vise, T-bolts and clamps or by special fixtures.

T-bolts and clamps are used for holding most of the work on the table.

Fixtures are used for holding repetitive work.

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