Jigs and Fixtures: Types, Parts, Advantages, Applications, and more

You might hear people say “jig” and “fixture” like they mean the same thing. They do similar jobs, but they work in different ways.

Jigs hold a cutting tool in place or guide it while it does a repeated job, like drilling or tapping holes. Fixtures don’t guide the tool. They just hold the workpiece steady in one position, orientation, or spot.

In this article, we’ll learn the small but important differences between these two manufacturing tools. We’ll see how they help improve quality, cut production costs, and make work more automatic.

What are Jigs and Fixtures?

Jigs and fixtures are devices that help make many identical parts faster. They also reduce the amount of human effort needed to make those parts.

People have already pointed out that a center lathe works well for making single parts in different shapes and sizes. But if you want to make many of the same part, using a center lathe is not cost‑effective.

On the other hand, a capstan and turret lathe fits repetitive work very well. Its multi‑tool setup and use of a transverse stop let it produce parts at a higher rate.

Still, not every kind of object can be machined on a capstan or turret lathe. Some jobs need drilling, milling, planing, grinding machines, and others.

If you want to make such objects in identical shapes and sizes on a large scale, you need the right devices to hold and locate them. That way, you can repeat the work accurately. These devices are jigs and fixtures.

Elements of jigs and fixtures

The main elements of jigs and fixtures are:

#1. Body.

It’s a plate, box, or frame that holds the parts you’re machining. It needs to be strong and stiff so it doesn’t bend or shake.

#2. Locating Elements.

These parts put the workpiece in the right spot relative to the cutting tool.

#3. Clamping Elements.

These parts hold the workpiece tightly in place once it’s located.

#4. Guiding and Setting Elements.

In a jig, these parts guide the cutting tool. In a fixture, they help set the tool so it works correctly.

#5. Positioning Elements.

These are different kinds of fasteners that attach the jig or fixture to the machine in the correct position.

#6. Indexing Elements.

You don’t always need these. But if the workpiece must move to different positions to machine different surfaces or locations, you add these parts to the jig or fixture.

What is a Jig?

A jig is a device that holds and locates a workpiece while it guides and controls one or more cutting tools. It keeps the work and the tool in the right positions relative to each other.

In construction, a jig is a plate, structure, or box made of metal or sometimes non-metal. It has features that let you handle components in the same position one after another. It then guides the tool to the correct positions on the work, following the drawing, specification, or operation layout.

Types of Jigs

The following are the seven different types of jigs.

1. Template jig
2. Plate jig
3. channel jig
4. Diameter jig
5. Leaf jig
6. Ring jig
7. Box jig

#1. Template Jig.

The template jig is the simplest type. You fix a plate (plate 2) with holes in the right spots onto the part you want to drill (component 1).

You guide drill 21 through those holes in template 2, and you drill the needed holes in the workpiece. The holes end up in the same positions relative to each other as the holes on the template.

#2. Plate Jig.

• A fixture holds and positions the work, but it does not guide the tool. A jig holds, locates, and guides the tool.
• Fixtures are heavier, and you bolt them firmly to the machine table. Jigs are lighter so you can handle them fast, and you often do not need to clamp them to the table.
• You use fixtures to handle work in milling, grinding, planing, or turning. You use jigs to hold work and guide the tool, especially in drilling, reaming, or tapping.

A plate jig improves the template jig by adding drill bushes to the template. You use the plate jig to drill holes in large parts while keeping accurate spacing between the holes.

#3. Channel Jig.

This jig has a channel-like shape. You fit component 1 inside channel 4, then you locate and clamp it by turning knurled knob 5. You guide the tool through drill bush 3.

#4. Diameter Jig.

You use this jig to drill radial holes in a cylindrical or spherical workpiece. You place work 1 on fixed V-block 6, then you clamp it with clamping plate 7 that sits on the work. You guide the tool through drill bushing 8, which you set radially with the work.

#5. Leaf Jig.

It has a leaf or plate 13 hinged on the body at 11, and you can swing the leaf open or closed to load or unload the work. You locate work 1 with buttons 10 and clamp it with set screws 12. Drill bush 3 guides the tool.

#6. Ring Jig.

You use this jig to drill holes in circular flanged parts. You clamp the work securely on the drill body, and you drill the holes by guiding the tool through drill bushes.

#7. Box Jig.

It has a box-like shape, and you locate the component inside it with buttons 18. You clamp work 1 by turning cam handle 19, which also locates it. Drill bush 3 guides the tool. You generally use box jigs to drill several holes on a component from different angles.

What is a Fixture?

A fixture is a device that holds and positions a workpiece during inspection or a manufacturing step. The fixture does not guide the tool.

In construction, the fixture is a standard or custom work-holding device that you clamp onto the machine so it can hold the work in place.

You set the tools at the needed spots on the work by using gauges or by adjusting them by hand.

Types of Fixtures

The following are the 10 different types of fixtures:

1. Turning fixtures.
2. Milling fixtures.
3. Broaching fixtures.
4. Grinding fixtures.
5. Boring fixtures.
6. Indexing fixtures.
7. Tapping fixtures.
8. Duplex fixtures.
9. Welding fixtures.
10. Assembly fixtures.

Fixtures are usually named after the type of machining operation for which they are designed and employed.

#1. Turning fixtures.

You can hold regular workpieces on lathes with standard tools like chucks, collets, centers, mandrels, or faceplates. But oddly shaped parts cause real trouble when you try to hold them right.

You can sometimes grip simple odd-shaped jobs in a chuck. For example, you adjust the jaws on a four-jaw chuck or use shaped soft jaws to fit the part.

But if a workpiece has a complicated shape, you need a turning fixture. These fixtures mount on the nose of the machine spindle or on a faceplate, and they hold the workpiece.

If the fixture is unbalanced, you add a counterweight to balance it.

Good turning fixtures follow a few rules:

• They grip the workpiece very firmly.
• They stay rigid and keep overhang as short as possible.
• They avoid dangerous projections that could hit the operator or the tool.
• They support thin or weak sections of the workpiece so those areas do not bend or break during cutting.

#2. Milling fixtures.

Milling fixtures hold and position workpieces during milling operations. You place the fixture on the machine table and lock it down with bolts and nuts.

You then move the table to set the cutter in the right spot. Before you start, you locate the workpiece on the base of the fixture and clamp it tight.

Milling creates high, sometimes jerky cutting forces, so the clamps must hold strong. To line up the fixture accurately, two tenons stick down from the fixture base. These tenons slide into a T-slot on the table and set the position. After that, you secure the base to the table with T-bolts and nuts.

#3. Broaching fixtures.

Broaching fixtures locate, hold, and support workpieces on different broaching machines. You use them for jobs like cutting keyways or broaching holes.

For internal pull-type hole broaching, a simple clamping plate can act as the fixture. It holds the part while the broach pulls through to cut the shape.

#4. Grinding fixtures.

Grinding machines use many kinds of fixtures to locate, hold, and support workpieces. These can be standard work-holding tools like chucks, mandrels, chucks with shaped jaws, or magnetic chucks.

For example, a vertical surface grinder with a rotary table usually has a rotary fixture bolted to its table. A plain or “string” fixture may sit on a surface grinder with a reciprocating table. A drill-grinding attachment is a common standard fixture used to grind drill geometry.

No matter what kind of fixture you design for grinding, it should:

• Stay properly balanced if it rotates.
• Allow coolant to flow in and out easily.
• Provide a place to mount wheel dressers.

#5. Boring Fixture.

The operation can be performed in one of the following two ways:

• By keeping the boring bar (tool) stationary and feeding the turning workpiece onto the bar.
• By keeping the workpiece stationary and feeding the rotating boring bar into the work.

Accordingly, the boring fixture is made in two common designs.

One type uses the same idea as a drilling jig. It guides the boring bar (the cutting tool) through a pilot bush. People also call this kind of fixture a boring jig. The other type holds the workpiece in the right position compared to the boring bar.

Even though this fixture uses almost all the usual jig and fixture design ideas, it does not need to be as strong as milling fixtures. That’s because it never has to handle cutting loads as heavy as the ones in milling operations.

#6. Indexing Fixture.

Some parts need machining on different surfaces so that the finished surfaces or shapes end up evenly spaced.

You have to index these parts the same number of times as the number of surfaces you need to machine. The holding devices (jigs or fixtures) include a suitable indexing mechanism. A fixture with this kind of device is called an indexing fixture.

#7. Tapping Fixture.

The tapping fixture positions and firmly holds identical workpieces so you can cut internal threads in drilled holes.

Odd-shaped and unbalanced parts always need these fixtures, especially when you tap the same kind of part over and over on a large scale.

#8. Duplex Fixtures.

This name describes a fixture that holds two similar parts at the same time and lets you machine both parts at two separate stations. While you machine one workpiece at one station, the other sits at the second station.

Both operations can be the same or different, depending on what you need. Once machining finishes at both stations, you rotate the fixture 180 degrees. This moves the first part to the second station for its next operation and moves the finished part back to the first station.

You then unload the finished part, put in a fresh part, and perform the first operation on it. The cycle keeps repeating, which lets you mass-produce parts at a pretty high speed.

#9. Welding Fixtures.

Welding fixtures hold and support the different parts you want to weld in the right places and keep the welded structure from warping.

To do this, you place the locating elements carefully, clamp lightly but firmly, and keep the clamps away from the welding area. The fixture must stay stable and rigid so it can handle the stresses from welding.

In many cases, a common practice is to tack weld the structure first while holding it in a welding jig, then move it to a holding fixture for the full weld.

This cuts down the chances of distortion a lot and puts less stress on the fixture.

#10. Assembly Fixture.

These fixtures hold different parts together in their correct relative positions while you assemble them. For example, you can hold two or more steel plates in place and rivet them.

People call these mechanical assembly fixtures because they hold parts for mechanical operations.

On the other hand, other types of fixtures hold parts for joining in different ways. Welding fixtures are also assembly fixtures, but they are for hot joining.

Difference Between Jigs and Fixtures

The following are the fundamental differences between a fixture and a jig:

Advantages of Jigs and Fixtures

Jigs and fixtures give you these benefits:

• They boost machining accuracy because they automatically position the workpiece and guide the tool, so you do not need manual adjustments.
• They raise production capacity by letting you machine many workpieces in one setup, and sometimes they let multiple tools cut at the same time.
• They cut handling time because you can set and locate the work quickly.
• They let you increase speed, feed, and depth of cut because jigs and fixtures hold the work very rigidly.
• They help you make identical parts that fit together easily, which makes assembly faster and simpler.
• They remove the need to mark out, measure, and do other setup steps before machining.
• They reduce the operator’s effort and tiredness, and they make handling steps smaller and easier.
• They allow a semi-skilled operator to run the job because the tool and work setup become mechanical, which saves labor costs.
• They lower the money you spend on quality control for finished products.
• They lower the total cost of machining by fully or partly automating the process.

Disadvantages of Jigs and Fixtures

Here are the downsides of jigs and fixtures:

• Over time, jigs and fixtures can wear out.
• The setup takes a lot of money and time at the start.
• They are heavy and need a lot of material to build.

Applications of Jigs and Fixtures

These are the main uses of jigs and fixtures:

• They can make car parts in large numbers.
• Steel factories use them to cut ingots.
• The refrigeration industry also uses them.
• Shops use them to drill holes at any needed angle and to drill flanges.
• Jigs handle mass drilling, reaming, and tapping.
• Fixtures support large turning, grinding, and milling jobs.