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Elements of Jig | Parts of a Jig

Elements of Jig

A JIG is a tool that holds the workpiece in position while being machined. Jigs are often used to hold parts in position before they are assembled together.


A jig is a fixture that holds parts while they are being machined. A jig may consist of several components, including a base plate, a tabletop, and a clamping system. The base plate is attached to the machine bed and provides stability to the workpiece. The table top is placed over the base plate and clamps down onto the workpiece. Clamping systems hold the workpiece securely in place.


A fixture is a tool that is designed to perform specific tasks. Fixtures are often used to hold work pieces steady while they are being machined. Fixtures may consist of many different components including a base plate and a tabletop.


Definition of Jig

The jig is a device that firmly holds and locates a workpiece and also guides the cutting tool during machining.

Jig body

This is also called the base. It supports the workpiece with locators and clamps. The base is fitted with four feet, which rest on the machine table.

Jig feet

The jig has four feet at the bottom. The jig rests on the machine table only with these feet. This increases accuracy. Jig feet are welded or cast with the jig body. Sometimes, feet are press-fitted. They are usually hardened and ground to a flat surface. In some cases, jig feet are not present.

Drill bush or latch

Drill bush guides tools like drills and reamers during machining. Bushes are fixed on jig plates or bush plates. These bushes are made of hardened steel. When the bush wears out, it can be replaced with a new one. There will be one bush for each hole to be drilled. The size of the bush depends on the size of the hole to be drilled.

Bush plate or Jig plate

Bushes are fitted to the bush plate. A bush plate may be a rigid one or maybe of a hinged type. A hinged type plate is called a leaf or latch. This can be swung open to load as well as unload the workpiece. It is swung again for closing.


Locators help the workpiece to rest in the proper position with reference to tools. Therefore, holes are drilled accurately in the required position. Locators are fitted in these holes. Depending upon the workpiece shape, various locators are used. Usually, locators are detachable types. They are fixed to the jig body or frame. Worn-out locators can be replaced by new ones.

Clamps or knobs

Clamps are used for holding the workpiece rigidly in its position; they also keep the workpiece firmly in contact with locating pins. Clamps should be thick enough so that they do not bend while clamping,. Generally, the surface of clamps is case hardened.

Foolproof element

This element prevents the loading of the workpiece in the wrong position. That is, this element makes sure that the workpiece is correctly loaded and positioned. Fouling pegs, cross pieces, or pins are used as a foolproof element.


What is Machining?

Machining is the act of removing material using tools and machines. In metalworking, machining is the removal of material from a piece of stock material (such as a bar) using cutting tools (drills, taps, milling cutters, etc.) and machine tools (lathes, mills, grinders, etc.). Machining may involve shaping, boring, reaming, threading, tapping, drilling, turning, grinding, polishing, sawing, shearing, punching, and welding.

What are cutting tools?

Cutting tools are the devices used to remove material from a workpiece. These tools are designed to create a specific shape or profile on the surface of the workpiece. Cutting tools can be hand-held or attached to a machine tool.

Hand-held cutting tools include chisels, gouges, scrapers, knives, scissors, files, planes, rasps, and saw blades. Machine-attached cutting tools include drills, endmills, face mills, lathes, milling cutters (also called rotary cutters), orbital cutters, planers, shapers, and saws.

What are fixtures?

Fixtures are devices that hold the workpiece steady while the cutting tool performs the operation. Commonly used fixtures include collets, chucks, vices, clamps, and holders. Collets clamp around the outside diameter of the workpiece. Chucks clamp around the inside diameter of the workpiece and are often used for turning.

Vices grip the workpiece at two points and allow the user to rotate the workpiece. Clamps grip the workpiece at only one point and are commonly used for milling. Holders keep the workpiece stationary while the cutting tool moves back and forth across the length of the holder.

Jig vs Fixture

A jig is a tool that holds workpieces while they are being cut, drilled, or otherwise worked upon. A fixture is a device that holds the workpiece steady while it is being worked upon. Both tools have their uses, but each has its own advantages and disadvantages.

Advantages of using a jig

  • You don’t need to worry about holding the workpiece steady while working on it.
  • If you use a jig, then you won’t need to spend time drilling holes in the workpiece.
  • Reduce manufacturing time—marking out; measuring, and setting the workpiece are not required. This saves time.
  • Increased dimensional accuracy: The workpiece is located automatically; the tool is properly guided in machining.
  • Identical parts are produced easily: Parts of the same size and shape are interchangeable. Therefore, assembly operations can be done without any difficulty.
  • Increase the rate of production:
  • Many workpieces are machined in a single setup.
  • Many tools cut workpieces at the same time.
  • Work handling time is reduced—this is due to the quick setting and locating of the workpiece.
  • The metal removal rate has increased.
  • The workpiece is rigidly clamped by jigs. Therefore, speed, feed, and depth of cut can be increased for machining. That is, more metal is removed in less time.
  • Operator fatigue is reduced.
  • Work handling operations such as marking, centering, and clamping are very much reduced. Hence, the operator’s fatigue is reduced.
  • Semi-skilled operators are adequate because the set of tools and work is simpler. The salary for semi-skilled labor is lower than for skilled labor.
  • Quality control costs are lower.
  • The overall cost of production is reduced.

Disadvantages of using a jag

  • You may not be able to get the exact angle you want.
  • You may need to drill additional holes if you want to attach something else to the workpiece.

Advantages and disadvantages of using a fixture

  • You can get the exact angle you need.
  • You can easily attach things to the workpiece.

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