UNIT VI Jigs and Fixtures Jigs and Fixtures

UNIT VI Jigs and Fixtures

“Jigs and Fixtures are the devices which are used to increase the production rate of similar parts and reduce human efforts”

� Eliminate the necessity of a special set up for each individual part � Assure high accuracy of the parts � Enable heavy and complex shaped parts to be machined. � Reduce quality control expenses � Less skilled labour can be utilized

“A device which holds and positions the work, locates or guides the cutting tool relative to the work piece and usually is not fixed to the machine table”

“A work holding device which only holds and positions the work but does not in itself , locates, guides or position the cutting tool and is bolted and clamped to the machine table” The setting of tool is done by , -Machine adjustment -Setting block -Slip gauges

Workpiece Slip Gauges

1. Body-Frame type structure 2. Locating Elements 3. Clamping Elements 4. Guiding and Setting Elements-for tool 5. Positioning Elements-fastening devices 6. Indexing Elements-not always provided

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Reduction of idle time Cleanliness Replaceable parts Coolant provision Hardened surface material Clamps position Easy manipulation Clearance Ejecting devices Economic consideration

“The incorporation of designing features in jig or fixture that will make it impossible to load the work into the jig or fixture in an improper position but will not interfere with proper loading and locating the work piece ” e. g. fouling pegs , blocks or pins

1. Translatory Motion 2. Rotary Motion

“ Work piece can be completely restrained with the help of three location points in one plane, two location points in the second plane and one location point in the third plane ”

1. 2. 3. 4. 5. Support Pins and Jack Pins Locating Pins V-Locators Bush Locators Angular Locators

1. Shape and size of work piece 2. Operation to be performed 3. Quantity and quality of work piece 4. Surface finish and accuracy available on the surface of work piece

1. Support Pins and Jack Pins • To avoid error due to unevenness of work piece surface

Support Pins

JACK PINS

2. Locating Pins

3. V-Locators • Effective , accurate and quick method of locating circular and semicircular work pieces • Fixed to jig or fixture body with the help of allen screws and dowels

4. Bush Locators

Bush Locator Cylindrical work pieces like shafts, axles, spindles can be located - For easy mounting and location , location faces of bushes are chamfered

5. Angular Locators • Used for components having previously finished holes

1. 2. 3. 4. 5. Lever Clamps Screw Clamps Latch Clamps Hinged Clamps Quick Acting Clamps

1. Lever Clamps

a. Heel Clamp

b. Bridge Clamping and releasing operations are speeded up by replacing hexagonal nut by a threaded handle

C. Edge Clamp For machining horizontal surface

2. Screw Clamps

Floating Pad- Screw Clamp To prevent work piece displacement To prevent screw deflection

3. Latch Clamps

Latch Clamp or Swinging Strap Clamp

4. Hinged Clamps

Hinged Clamp

5. Quick Acting Clamps

Jig Bushes Locate and Guide the cutting tools e. g. drills , reamers and boring tools Material-Mild Steel, Cast Iron

1. Fixed Bushes � � � Plain Bushes Flanged Bushes Screwed Bushes 2. Liner Bushes 3. Slip or Renewable Bushes

Plain or Headless Bushes- for a single tool Flanged Bushes-for greater length of bore

Prevents bush from lifting and secured rigidly in bush plate

Quick removal and replacement Retaining Screw-Prevents rotation and lift of bushes Liner Bushes- Press fitted and support renewable bushes

Indexing Jigs and Fixtures “ Indexing is preferred where there is a relation between holes or slots to be machined, in a work piece “

1. Indexing Plate 2. Sliding Indexing Device

Types of Jigs 1. Drilling Jigs 2. Boring Jigs

Used when holes are to be drilled in more than one plane of a work piece

Used for drilling holes in circular components having internal and external diameter The body of jig is in the form of a pot

Used to drill holes in collars and hubs of pulleys and gears etc

Types of Fixtures Milling Fixtures Turning Fixtures Broaching Fixtures Welding Fixtures

Turning Fixtures

Welding Fixture

University Problems

Thank You…