Machinery's Handbook, 31st Edition
Right-Angle Plates 761 Type V, Toolmaker’s Adjustable Angle Plate: The toolmaker’s adjustable knee or adjust able angle plate extends the capabilities of the right-angle plate and allows for precise adjustment of the support table or bearing surface from 0 ° (horizontal) through 90 ° (verti cal), Fig. 5 . The same tolerances in regard to flatness and squareness apply to the bearing surface and the base. The toolmaker’s adjustable knee is constructed of a plate, finished to the tolerances determined by the class specified, and a right-angle iron with two ribs. The right-angle iron and the plate are joined together by a precision hinge that has the capability to be secured at any position within the arc from 0 ° to 90 ° . The two ribs are of sufficient thickness to provide stability and support enough to withstand the forces applied during boring, milling, drilling, or grinding operations. The locking mechanism must be capable of maintaining its locked position under the same circumstances. The table is provided with T-slots for the mounting of the workpiece. The quadrant scale of the adjustable angle plate is divided into 90 divisions and a vernier scale. The vernier scale is graduated into 5 minute divisions from 0 to 60 minutes on either side of the zero index. The 0 (zero index) and every 15 minute index thereafter on both sides of 0 is clearly marked with the corresponding number, and the 5 minute divisions are clearly readable. The quadrant scale has 1 degree divisions from 0 ° to 90 ° . The zero index and every 10 ° index following will be clearly marked with the corresponding number. A tolerance not to exceed plus or minus 2 minutes, noncumulative, is given for the error between any two graduations. Due to its specialized nature, the toolmaker’s adjustable angle plate usually is only man ufactured in one size according to the GGG-P-441A Federal Specification. Type VI: Toolmaker’s Non-Adjustable Angle Plate: The Type VI toolmaker’s nonadjust able right-angle plate is different from the other types in that it has two members. These members have two working surfaces at right angles to each other as well as a finished pad on the back of both working surfaces. The design is of sufficient thickness along with the ribbing to insure rigidity and stability in all operations and applications.
X
Y
Z Fig. 6. Type VI, Toolmaker’s Non-Adjustable Knee
Both front sides and the back side pads are considered functional working surfaces and will be manufactured according to the grade specified. The working surfaces, the opposite sides, and the opposite ends are all machined parallel to each other and square to their respective working surfaces. All machined surfaces will meet the tolerance limits assigned to the specified grade for finish, flatness, squareness, and parallelism. The Type VI toolmaker’s nonadjustable right-angle plate will appear similar to Fig. 6. Calibration and Maintenance of Right-Angle Plates.— In many machine shops and quality assurance programs, right-angle plates are not calibrated and are considered “Calibration Not Required” or “Reference Only” instruments that are not placed into the calibration recall system. Inevitably, this practice may lead to unknown error in a manufacturing operation or inspection procedure. However, calibration of a right-angle plate may be an investment in quality if it becomes evident that an angle plate that has worn
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