Machinery's Handbook, 31st Edition
Right-Angle Plates 759 Angle Plate Types.— The right-angle plate is further divided into Types and Classes , each type having unique characteristics and uses. Types I, II, and III angle plates or knees are intended to be used by craftsmen for ordinary machine shop operations; Types IV, V, and VI are intended to be used principally by toolmakers and for precision type work. Type I: Class 1-Plain Right-Angle Plate and Class 2-Slotted Right-Angle Plate: The Type I Class 1 angle plate has two members with the outside surfaces at right angles to each other. Both the working surfaces and the ends are machined square to within the tolerance limits assigned to their grade, (Fig. 1a). Type I Class 2 plates are similar to Class 1 with the vertical and horizontal slots provided on one or both faces, (Fig. 1b).
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X Z Fig. 1a. Type 1 Class 1-Plain
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Fig. 1b. Type 1 Class 2-Slotted
Fig. 1c. Type 1 Class 3, Measuring-Plain
All the right-angle plates of the various types have ribbing of sufficient thickness to assure maximum support for flatness, squareness, and stability. Class 1 plates of approxi mately 10 to 12 inches will have at least 2 ribs, those of 16 to 24 inches at least 3 ribs, and those of 36 inches and above a minimum of 4 ribs in their design. Plates weighing over 75 pounds are designed with lifting holes in the ribbing or threaded holes for the placement of lifting eyes. Type I, Class 3, Measuring Plane Right-Angle Plate: The Type I Class 3 angle plate, Fig. 1c, is designed to establish a measuring plane for production or inspection functions. It has two outside working surfaces that are at right angles to each other. The working surfaces are finished according to the grade specified and are the only two faces designed for functional operation. Unless specifically ordered otherwise, the sides and ends will be finish ground only, and these surfaces are not to be used to determine or establish squareness. The rib provides support between the ends of the plate and is cored out to provide a good hand gripping surface without sacrificing the stabilizing effect of the rib. The short base member “Y” is provided with a suitable hole so the plate may be bolted to the table of a machine or a tapped hole in a surface plate. Type II, Inside Right-Angle Plate: The Type II right-angle plate is an inside right angle that is constructed with the same adherence to squareness and finish as the outside angle plates, Fig. 2. The inside angle plate is an inverted T-shaped casting formed by a base and a perpendicular member of approximately the same thickness. One side of the perpendicular, the adjacent top side of the base, and the bottom of the base are the three working surfaces and are all finished in accordance to the grade specified. The opposite ends and opposite sides are machined parallel and square to their respective working surfaces.
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Fig. 2. Type II, Inside Right-Angle Plate
Fig. 3. Type III, Universal Right-Angle Plates
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