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3-2-1 method
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An effective method for locating a rectangular workpiece. Three datum points support the workpiece, two datum points locate a flat workpiece surface, and a single datum point locates a second surface perpedicular to the previous surface.
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base plate
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A precisely ground plate that acts as the foundation of a fixture. Various components, such as locators and clamps, are fastened to the base plate.
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clamping
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The appropriate forces used to hold a workpiece against the locators during the machining operation.
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external locating
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The use of external surfaces to locate a workpiece. The 3-2-1 method is an external locating method.
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fixture
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A customized workholding device used on machine tools to position and hold a part during various machining operations. A fixture is built to hold a specific part design.
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ground
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Machined with an abrasive to achieve highly accurate measurements.
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hydraulic power
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Power created by water or fluid pressure.
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inspection fixture
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A fixture used to hold a workpiece while it is being examined. Inspections usually involve comparing workpieces with desired measurements for accuracy.
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internal locating
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The use of internal surfaces to locate a workpiece. The most common internal locating method is the use of a round and relieved pin to locate two machined holes.
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locating
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The accurate positioning of the workpiece in a horizontal plane to establish a relationship between the workpiece and cutting tool.
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locating pin
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An assembled locating device that can be used to locate either an outside workpiece surface or an interior hole. Locating pins are available in numerous shapes and sizes.
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lot size
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The number of parts created during the use of a particular tooling setup.
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nonproductive time
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Time that is spent without the machine in operation producing chips. Nonproductive time includes setup time, changing of parts, equipment failure, etc.
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plate fixture
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A fixture consisting of assembled components such as a base plate, locating pins, rest buttons, clamps, etc.
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pneumatic power
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Power created by air pressure.
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power clamping
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A clamping system that converts hydraulic or pneumatic power into mechanical clamping forces.
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relieved pin
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A locating pin with a diamond-shaped head that is used to position a workpiece in only two opposite directions. Relieved locators are most often used with an internal locating pin.
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rest button
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A short locating pin that is used to both support and locate a workpiece.
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setup time
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Time that is spent setting up the fixture, calculating tool offsets, and performing all the necessary tasks to produce the first accurate part.
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strap clamp
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A type of clamp that reaches over the workpiece to hold it in place. Strap clamps are often used when extra toughness is required.
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supporting
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The process of locating from underneath the workpiece. Supports generally restrict motion down along the Z-axis.
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toe clamp
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A type of low-profile clamp with a serrated surface that reaches forward and down to grip the workpiece on its edge.
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toggle clamp
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A type of clamp that operates on a pivot and lever system. Toggle clamps have a limited clamping range.
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tolerance
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An unwanted but acceptable deviation from the specified dimension.
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tool steel
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A specialized type of alloy steel that has excellent strength, toughness, and wear resistance. Tool steels are used in cutting tools, punches, and other industrial tooling.
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workholding device
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A device used to support, locate, and hold a workpiece during machining. The workholding device accurately references the tool performing the operation on the part being held.
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