work holding devices-milling, shaping, planing & slotting machines
DESCRIPTION
standard work holding devicesTRANSCRIPT
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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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