Richard Perry What Is a jig | Types of Jigs | Jigs of Jigs and Fixtures

Created by Richard Perry

Types of Jig:

  • The most common type of jig is a drill jig, used to guide drill bits to make holes at specific locations; examples of drill jigs are box jig, angle plate jig, sandwich jig, and channel jig.
  • Wooden working jigs are widely used to create complex wooden profiles.
  • There are also other types of jigs, including template jig, plate jig, diameter jig, ring jig, indexing jig, welding jig, jeweler jig, and others.

Tool Bodies

The tool body provides the mounting area for all the locators, clamps, supports, and other devices that position and hold the workpiece. The specific design and construction of a tool body are normally determined by the workpiece, the operations to be performed, and the production volume. Economy is also a key element in good design.

The three general categories of tool bodies are cast, welded, and built up, Figure 4-1. Each type of construction can be used for any workpiece, but one is often a better choice than the others. The first step toward an economic design is to know and weigh the strengths and weaknesses of each.

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Cast tool bodies are made in a variety of styles and types. The most common casting materials for tool bodies include cast iron, cast aluminum, and cast magnesium. Cast materials occasionally found in specialized elements for tool bodies, rather than in complete tool bodies, are low-melting-point alloys and epoxy resins.

Cast tool bodies can have complex and detailed shapes. Such shapes require fewer secondary machining operations. Cast materials dampen vibration. They are most often found in relatively permanent workholders; workholders not subject to drastic changes. Cast tool bodies have three major drawbacks: (1) they are not easily modified for part changes; (2) their fabrication cost is high; (3) they require a lengthy lead time between design and finished tool body.

Welded tool bodies are also made from a wide variety of materials. The most common welded tool bodies are made of steel or aluminum. Welded tool bodies are inexpensive to build and they are usually easy to modify.

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They require minimal lead time. Welded tool bodies are also quite durable and rigid. They provide an excellent strength-to-weight ratio.

Heat distortion is the major problem with welded tool bodies. For best results, and to ensure stability of the tool body, welded tool bodies should be stress relieved before final machining and use.

Be aware, however, this will add to the preparation lead time and cost, as well. Another problem with welded tool bodies is in the use of dissimilar materials. When a steel block, for example, is added to an aluminum tool body, it should usually be attached with threaded fasteners rather than by welding to the body.

Built up tool bodies are the most common tool body today. These tool bodies are very easy to build, and usually require the least amount of lead time between design and finished tool. The built up tool body is also easy to modify for changes in the part design.

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Like the welded body, built up tools are durable and rigid, and have a good strength-to-weight ratio. Depending on the complexity of the design, the built up tool body may be the least expensive to construct.

Built up tool bodies are usually made of individual elements, assembled with screws and dowel pins. The built up tool body is often used for precision machining operations, inspection tools, and some assembly tooling.

Preformed materials can often reduce the cost of machining tool bodies. These preformed materials include precision tooling plates, tooling blocks, risers, cast sections, and angle brackets. Other materials include ground flat stock, drill rod, or drill blanks, and also structural sections such as steel angles, channels, or beam.

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The major advantage to using preformed and standard parts is the reduced labor cost in fabricating the workholder.

Tooling Plates

Tooling plates are standard, commercially available base elements used to construct a variety of different workholders. Like other fixturing elements, these plates come in several variations to meet most fixturing requirements.

Rectangular Tooling Plates: Of all standard tooling plates, the rectangular ones, Figure 4-2, are the most popular. Their rectangular form works well for a wide variety of workholders. The plates come in a wide range of sizes, from 12” x 16” to 24” x 32”. Rectangular tooling plates are made of ASTM Class 40 gray cast iron, machined flat and parallel.

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Round Tooling Plates:  Another tooling-plate variation is the round tooling plate, Figure 4-3. Round tooling plates work well on rotary or indexing tables. These tooling plates are available in 400mm, 500mm, and 600mm diameters. They are made of ASTM Class 40 gray cast iron, and have a series of mounting holes.

Square Pallet Tooling Plates:  Square pallet tooling plates, Figure 4-4, are another form of tooling plate.

The square shape is ideal for palletized arrangements where a square tooling base is necessary. Square tooling plates come in five sizes to fit standard machining-center pallets 320mm, 400mm, 500mm, 630mm, and 800mm square. Plates are made of ASTM Class 40 gray cast iron.

Rectangular Pallet Tooling Plates. Similar to square pallet tooling plates, except made for rectangular machining-center pallets 320 x 400mm, 400 x 500mm, 500 x 630mm, and 630 x 800mm. Figure 4-5 shows this type, and how it can also be mounted on a square pallet by adding a spacer.

Angle Tooling Plates. The angle tooling plates, Figure 4-7, are another useful tooling plate. These vertical plates allow mounting a large part approximately on the pallet’s center-line. These plates are made to fit machining-center pallets 400mm, 500mm, 630mm, and 800mm square. Angle tooling plates are made from ASTM Class 45 cast iron.

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Platform Tooling Plates. Platform tooling plates are a variation of the square tooling plate. These plates are specifically designed for a mounting surface that must be elevated off the machine-tool table. As shown in Figure 4-6, the raised mounting surface permits easier access to the workpiece with horizontal machining centers. The added height provides the necessary clearance for the machine-tool spindle. The design also eliminates the dead space between the machine-tool table and the minimum operating height of the spindle.

Added height is also beneficial when machining short parts on a vertical machining center to avoid Z-axis limit errors. Platform tooling plates come in three sizes for 500mm, 630mm, and 800mm pallets. Platform tooling plates are made of ASTM Class 45 cast iron.

Tooling Blocks

Tooling blocks are often used on horizontal machining centers. The most-common tooling blocks are the two-sided and four-sided styles. These blocks work both for mounting workpieces directly, or for mounting other workholders. All working faces are accurately finish mac hined to tight tolerances, and qualified to the base.

Dual mounting capability, Figure 4-8, allows both JIS mounting (locating from two reference edges) and DIN mounting (locating from center and radial holes).

Two-Sided Tooling Blocks. The two-sided tooling block, Figure 4-9, is for mounting workpieces or workholders on two opposite sides. Two-sided tooling blocks work well for fixturing two large workpieces.

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These tooling blocks come in five different pallet sizes: 320mm, 400mm, 500mm, 630mm, and 800mm.

Four-Sided Tooling Blocks.  The four-sided tooling block, Figure 4-10, mounts workpieces or workholders on four identical sides. Four-sided tooling blocks, with their four working surfaces, are typically chosen to maximize production. These tooling blocks are available in five different pallet sizes: 320mm, 400mm, 500mm, 630mm, and 800mm.

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