Work Holding Devices-Milling, Shaping, Planing & Slotting Machines

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Work holding Devices of Milling, Shaping, Planing & Slotting Machines

Done by R. MUKHIL 14M439

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 Device

Work Holding Devices of Milling Machines

! 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.

Tool Maker Universal Vise

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.

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.

Dividing Head

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

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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.

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T-Bolts & Clamps

Bulky work pieces of irregular shapes are clapped directly on the milling machine table

by using T-Bolts and Clamps

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Work Holding Devices of Shaping Machine

! Vise is a quick method of holding and locating relatively small and regular

shaped work pieces.

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Shaper Vise

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.

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! 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.

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Clamping work on the Table

! Stop Pins & Toe Dogs

! While holding thin work on the table, stop pins in conjunction with toe dogs

are used.

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! Strip and Stop Pins: Work having sufficient thickness is held on the table by

strip and stop pins.

! Angle Plate

! V-Block

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! This is a special attachment used for cutting equally spaced grooves or

splines on the periphery of a round work.

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Shaper Centres

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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

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! 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.

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Special Fixtures

! 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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Work Holding Devices of a Slotting Machine

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