Jig and Fixture Design Chapter 1: Types and Functions of Jigs and Fixtures
Purpose of Tool Design Objectives: Provide simple, easy-to-operate tools for maximum efficiency Reduce manufacturing expenses by producing parts at the lowest possible cost Design tools that consistently produce parts of high quality Increase the rate of production with existing machine tools Design the tool to make it foolproof and to prevent improper use Select materials that will give adequate tool life Provide protection in the design of the tools for maximum safety of the operator
Jigs and Fixtures Production-workholding devices used to manufacture duplicate parts accurately Designed and build to hold, support, and locate every part to ensure that each is drilled or machined within the specified limits So closely related, sometimes confused or used interchangeably Difference the way the tool is guided to the workpiece
Jig Special device that holds, supports, or is placed on a part to be machined Locates and holds workpiece, also guides cutting tool as the operation is performed Usually fitted with hardened steel bushings for guiding drills or other cutting tools
Fixture Production tool that locates, holds, and supports work securely so the required machining operations can be performed Set blocks and feeler or thickness gauges are used with fixtures to reference the cutter to the workpiece Securely fastened to the table of machine during work done Simplify metalworking operations performed on special equipment
Classes of Jigs Boring Jigs Bore holes that either too large to drill or must be made an odd size Drill Jigs Drill, ream, tap, chamfer, counterbore, countersink, reverse spotface, reverse countersink Difference size of bushings used
Boring Jigs
Drill Jigs
Types of Jigs Drill Jigs Open Jigs Simple operations, work done on only one side of part Closed Jigs Box Jigs For parts that must be machined on more than one side
Types of Jigs Template Jigs Accuracy rather than speed Fits over, on or into work & not usually clamped Least expensive & simplest type With or without bushings (whole jig plate hardened) Plate Jigs Similar to Template Jigs Difference built-in clamps to hold work With or without bushings
Types of Jigs Table Jigs Style of Plate Jigs With legs to raise jig off table for large work Sandwich Jigs Form of Plate Jigs but with a back plate Ideal for thin or soft part bend or wrap Use of bushings depend on number of parts
Types of Jigs Angle-plate Jigs Hold parts that are machined at right angles to mounting locators Pulleys, collars, and gears are some of the parts used Clearance problems with cutting tool Modified Angle-plate Jigs For machining angles other than 90 Clearance problems with cutting tool
Types of Jigs Box/Tumble Jigs Totally surround part Part to be completely machined on every surface without the need to reposition the work in jig Channel Jigs Simplest form of Box Jigs Work held between two sides & machined from third side When jig feet are used, work can be machined on three sides
Types of Jigs Leaf Jigs Small box jigs with hinged leaf to allow easier loading & unloading Difference size & part location with box jigs Smaller & do not completely surround part Equipped with handle for ease of movement Indexing Jigs Accurately space holes or other machined areas around part by using part itself or reference plate and plunger
Types of Jigs Rotary Jigs Larger Indexing Jigs Trunnion Jigs Form of Rotary Jigs for very large or odd-shaped parts Put in box-type carrier & loaded on trunnion Suited for large, heavy parts that must be machined with several separate Plate-Jigs
Types of Jigs Pump Jigs Commercially made jigs, must be adapted by user Lever-activated plate makes this tool very fast to load & unload Time saver Multistation Jigs Differenct processes can be done at the same time Final station unloading finished parts & loading fresh parts Used on single-spindle & multispindle machines
Types of Fixtures Plate Fixtures Angle-Plate Fixtures Vise-jaw Fixtures Indexing Fixtures Multistation Fixtures Duplex Fixtures Profiling Fixtures
List of Production Operations Use Fixtures Assembling Boring Broaching Drilling Forming Gauging Grinding Heat Treating Honing Inspecting Lapping Milling Planing Sawing Shaping Tapping Testing Turning Welding Stamping