Till now, we know that jigs and fixtures are the devices which help in the machining of jobs and reducing the human efforts required for producing these parts. It has been explained before why a centre lathe is an ideal machine tool for creating individual pieces of different shapes and sizes, but for manufacturing similar objects in high number, its use is not that economical.
Different types of objects may require the use of drilling,milling, planning, and grinding machines, etc. Specific tools are necessary for producing these objects in identical shapes and sizes on a mass scale, by holding and locating tasks to minimize the repetition work. That is when various types jigs and fixtures come into play.
Considering the variety in the nature of jobs to be machined, the quality, and the associated functions, the type of jig and fixture varies as well. Following are the various kinds of jigs and fixtures.
Types of Jigs
Template Jig: The template jig is the simplest of all the models. The plate, having two holes, acts as a template which is fixed on the component to be machined.The drill is guided through these holes of the template and the required holes are drilled on the work-piece at the same relative positions with each other as on the template.
Plate Jig: A plate jig is an improvement of the template jig by incorporating drill bushes on the template.The plate jig is employed to drill holes on large parts maintaining accurate spacing with each other.
Channel Jig: Channel jig is a simple type of jig having a channel-like cross section. The component is fitted within the channel and is located and clamped by rotating the knurled knob. The tool is guided through the drill bush.
Diameter Jig: Diameter jig is used to drill radial holes on a cylindrical or spherical workpiece.
Leaf Jig: Leaf jig has a leaf which may be swung open or closed on the work for loading or loading purposes.
Ring Jig: Ring jig is employed to drill holes on circular flanged parts. The work is securely clamped on the drill body, and the holes are drilled by guiding the tool through drill bushes.
Box Jig: Box jig is of box-like construction within which the work is rigidly held so that it can be drilled or machined from different angles at a single setting depending on which face of the jig is turned toward the tool.
Types of Fixtures
Turning Fixtures: These fixtures are generally mounted on the nose of the machine spindle or a faceplate, and the workpieces held them. Whenever necessary, the fixture may have to be provided with a counterweight or balance the unbalance fixture.
Milling Fixtures: Milling fixtures are typically mounted on the nose of the machine spindle or a faceplate, and the work-pieces held them.The table is shifted and set in proper position, in relation to the cutter. The work-pieces are located in the base of the fixture and clamped before starting the operation.
Broaching Fixtures: Broaching fixtures are used on different types of broaching machines to locate, hold and support the workpieces during the operations, such as keyway broaching operations, such as keyway broaching, hole broaching, etc.
Indexing Fixtures: Several components need machining on the different surface such that their machined surface surfaces or forms are evenly spaced. Such elements are required to be indexed equally as many as the number of surfaces to be machined. The holding devices (jigs or fixtures) used are made to carry a suitable indexing mechanism. A fixture carrying such a device is known as an indexing fixture.
Grinding Fixtures: These fixtures may be the standard work-holding devices, such as chucks, mandrels, chuck with shaped jaws, magnetic chucks, etc.
Boring Fixtures: This fixture incorporates almost all the prevailing principles of jig and fixture design, their construction need not be as sturdy as that of the milling fixtures, because they never have to bear as heavy cutting loads as involved in milling fixtures, because they never have to endure as heavy cutting loads as involved in milling operations.
Tapping Fixtures: Tapping fixture is specially designed to position and firmly secure identical work-pieces for cutting internal threads in drilled holes in them. Odd shaped and unbalanced components will always need the use of such fixtures, especially when the tapping operation is to be carried out repeatedly on a mass scale on such parts.
Duplex Fixtures: It is the name given to the fixture which holds two similar components simultaneously and facilitates simultaneously machining of these components at two separate stations.
Welding Fixtures: Welding fixtures are carefully designed to hold and support the various components to be welded in proper locations and prevent distortions in welded structures. For this, the locating element need to be carefully; clamping has to be light but firm, placement of clamping elements has to be clear of the welding area. The fixture has to be quite stable and rigid to withstand the welding stresses.
Assembly Fixtures: The function of these fixtures is to hold different components together in their proper relative position at the time of assembling them.