Machinery's Handbook, 31st Edition
Right-Angle Plates 763 to remove any burrs on the edges or surfaces prior to beginning the calibration process. After the right-angle plate is clean and free from burrs, the TI is placed on the surface plate as shown in Fig. 8 . There is no need for a leveling plate as the side opposite is finished and parallel to the working surface, and the parallelism feature is what is being indicated.
TI TI Measuring Planes Detail A
Electronic Height Gage
Leveling Plate
Surface Plate
Fig. 8. Measuring Flatness/Parallelism of Type III Right-Angle Plate Using the electronic indicator as before, indicate the surface in the Union Jack pattern and record the maximum plus and the maximum minus readings overall. In general, it is a good idea to zero the electronic indicator in the center of the Union Jack and take the readings from that point. This provides an easily repeated starting point and an overall numerical picture of the parallelism of the surface. As before, subtract the minimum read ing from the maximum; the result must meet the tolerance limits specified by the man ufacturer or GGG-P-441A. Repeat this process for the remaining sides. All results must meet the stated tolerances. Squareness Calibration (Preferred Method) The simplest method that can be used to verify the squareness of the Type III universal right-angle plate, as well as the squareness of the other types, is quite sufficient when done properly to meet the accuracy ratio that is required for a high confidence level measurement. This method provides quantifiable data that can be assigned an uncertainty should the Quality System determine this necessary. This method provides a good measurement to verify the squareness value and identify any out of tolerance conditions before the error is passed on into the manufacturing or inspection process. Place the angle plate (TI) on the surface plate with two 0.1005-inch gage blocks between the face of the angle plate and the face of the granite angle block, as shown in Fig. 9a.
Granite Angle Block
Granite Angle Block
TI
TI
Gage Blocks
Gage Blocks
Surface Plate Fig. 9b. Gage Blocks Between Rotated TI and Granite Angle Block
Surface Plate
Fig. 9a. Gage Blocks Between TI and Granite Angle Block
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