Page 129 - CITS - Fitter - Trade Theory

FITTER - CITS

Fixture

Definition of Fixture
A fixture is a work-holding or support device used in the manufacturing industry. Fixtures are used to securely
locate (position in a specific location or orientation) and support the work, ensuring that all parts produced using
the fixture will maintain conformity and interchangeability. Using a fixture improves the economy of production by
allowing smooth operation and quick transition from part to part, reducing the requirement for skilled labour by
simplifying how work pieces are mounted, and increasing conformity across a production run.
Types of Fixture
A Milling Fixture:

A Milling fixture is a work holding device which is firmly clamped to the table of the milling machine. It holds the
work piece in correct position as the table movement carries it past the cutter or cutters.
- Positioned and secured on the milling machine table.

- Work pieces are located on the fixture base and clamped before milling.
B Drilling Fixture:
Drilling fixtures cover a wider range of different designs and procedures than milling fixtures. Though work
holding for drills is more often provided by jigs, fixtures are also used for drilling operations.
C Boring Fixture:
Designed for boring operations with two common designs. May incorporate a drilling jig or focus on work piece
positioning.
- Designed for boring operations with two common designs.
- May incorporate a drilling jig or focus on workpiece positioning.
D Turning Fixture: The standard work holding devices or fixtures for lathe are:

• Three and four jaw chucks
• Collars
• Face plate
• Mandrels

• Milling vice
- Used for holding irregularly shaped components during turning operations.
- Provides stability, minimises overhang, and ensures secure clamping.
If the job can be held easily and quickly in the above mentioned standard devices, then there is no need for special
work holding devices. However, many jobs particle casting and
forging, because of their shapes, cannot be conveniently held by any of the standard devices. It then becomes
necessary to build a special work holding device for the job. Such a device is called lathe fixture
E Assembly Fixture: Used to hold components together during assembly operations. Enables precise positioning
and joining of various parts, such as riveting or welding.

- Used to hold components together during assembly operations.
- Enables precise positioning and joining of various parts, such as riveting or welding.
F Welding Fixture: Welding fixtures are used to hold subcomponents of a welded assembly in place for
fabrication together into one complete unit. These fixtures are often actuated using manual (hand) clamps or
pneumatic clamps if paired with robotic automation. A robust robotic arc welding fixture is a part-holding tool
used to constrain components for welding in an automated system. Welding fixtures locate parts using these
clamps to secure important aspects of the subcomponent, such as holes, slots, or datum surfaces.

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CITS : CG & M - Fitter - Lesson 20