JIGS AND FIXTURES Flashcards
A device which holds and positions the work, locates or guides the cutting tool or relative to the work piece and it is not fixed to the machine table. lighter in construction
Jig
Work-holding device which only holds and positions the work, but does not in itself guide locate or position the cutting tool. Heavier in construction
Fixture
Used for Drilling, Reaming, and Tapping, and counter boring etc.
Jigs
Used in connection with turning, milling, shaping, and grinding
Fixtures
called production device
Jigs
Called inspection device
Fixture
Give 3 basic purposes of developing and using suitable jigs and fixtures for batch production in machine shops
to eliminate marking, punching, positioning, alignments etc.
easy, quick and consistently accurate locating, supporting and clamping the blank in alignment of the cutting tool
guidance to the cutting tool like drill, reamer etc.
increase in productivity and maintain product quality consistently
to reduce operator’s labour and skill – requirement
to reduce measurement and its cost
enhancing technological capacity of the machine tools
reduction of overall machining cost and also increase in interchangeability.
PRINCIPLES OR RULES OF LOCATING IN JIGS AND FIXTURES
For accurate machining, the workpiece is to be _______________________________ in the fixture (or jig) which is again appropriately located and fixed with respect to the cutting tool and the machine tool.
placed and held in correct position and orientation
PRINCIPLES OR RULES OF LOCATING IN JIGS AND FIXTURES
It has to be assured that the , once fixed or clamped, does not move at all.
blank
PRINCIPLES OR RULES OF LOCATING IN JIGS AND FIXTURES
Any solid body may have maximum ______ degrees of freedom (translation motion and rotational motion)
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PRINCIPLES OR RULES OF LOCATING IN JIGS AND FIXTURES
By properly locating, supporting and clamping the blank its all _______________ are to be arrested
degrees of freedom
One or more _________ (preferably machined) and / or drilled / bored hole(s) are to be taken for reference
surfaces
The _________________ should be significant and important feature(s) based on which most of the dimensions are laid down
reference surfaces
Locating should be easy, quick and accurate
In case of locating by pin, the pins and their mounting and contact points should be _______, ________, and _______
Strong, rigid, and hard
The locating pins should be ______________
- Use minimum locating points
- Use mutually perpendicular planes
as far apart as feasible
Design Principle Common to Jigs and Fixtures; Jigs and fixtures should be sufficiently stiff to secure the
preset accuracy of machining.
Rigidity
Design Principle Common to Jigs and Fixtures; the incorporation of design
feature in the jig or fixture that will make it possible to lead the work into jig and fixture, in an improper position , but will not interfere with loading and unloading the work piece.”
Fool Proofing
Design Principle Common to Jigs and Fixtures; to allow for any variation in component sizes specially casting and
forging. To allow for hand movements so that the work piece can easily
placed in the jig or fixture and removal after machining .
