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PRECISION MEASURING EQUIPMENT
Nomenclature of an outside micrometer

Aviation Boatswains Mate F - Aviation theories and other practices
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micrometer setting types (fig. 2-35). When using the deflecting beam and the dial indicating torque wrenches, the torque is read visually on a dial or scale mounted on the handle of the wrench. To use the micrometer setting type, unlock the grip and adjust the handle to the desired setting on the micrometer-type scale, then relock the grip. Install the required socket or adapter to the square drive of the handle. Place the wrench assembly on the nut or bolt and pull in a clockwise direction with a smooth, steady motion. (A fast or jerky motion will result in an improperly torqued unit.) When the torque applied reaches the torque value, indicated on the handle set- ting, a signal mechanism will automatically issue an audible click, and the handle will release or “break, ” and move freely for a short distance. The release and free travel are easily felt, so there is no doubt about when the torquing process is complete. Manufacturers’ and technical manuals generally specify the amount of torque to be applied. To assure getting the correct amount of torque on the fasteners, it is important that you use the wrench properly ac- cording to manufacturers’ instructions. Use that torque wrench that will read about mid- range for the amount of torque to be applied. BE SURE THAT THE TORQUE WRENCH HAS BEEN CALIBRATED BEFORE YOU USE IT. Remember, too, that the accuracy of torque measuring depends a lot on how the threads are cut and the cleanliness of the threads. Make sure you inspect and clean the Figure 2-35.—Torque wrenches. threads. If the manufacturer specifies a thread lubri- cant, it must be used to obtain the most accurate torque reading. When using the deflecting beam or dial indicating wrenches, hold the torque at the de- sired value until the reading is steady. Torque wrenches are delicate and expensive tools. The following precautions should be observed when using them: 1. When using the micrometer setting type, do not move the setting handle below the lowest torque setting. However, place it at its lowest setting before returning it to storage. 2. Do not use the torque wrench to apply greater amounts of torque than its rated capacity. 3. Do not use the torque wrench to break loose bolts that have been previously tightened. 4. Do not drop the wrench. If dropped, the accu- racy will be affected. 5. Do not apply a torque wrench to a nut that has been tightened. Back off the nut one turn with a nontor- que wrench and retighten to the correct torque with the indicating torque wrench. 6. Calibration intervals have been established for all torque tools used in the Navy. When a tool is cali- brated by a qualified calibration activity at a shipyard, tender, or repair ship, a label showing the next calibra- tion due date is attached to the handle. This date should be checked before a torque tool is used to ensure that it is not overdue for calibration. MICROMETERS The type of micrometers commonly used are made so the longest movement possible between the spindle and the anvil is 1 inch. This movement is called the range. For example, a 2-inch micrometer has a range from 1 inch to 2 inches, and only measures work be- tween 1 and 2 inches thick. Therefore, you must first determine the approximate size, to the nearest inch, of the piece to be measured and then select the proper size micrometer. The size of a micrometer indicates the size of the largest work it can measure. Outside Micrometer The nomenclature of an outside micrometer is illustrated in figure 2-36. 2-24







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