There is no perfect method for finding the elements of internal threads. But even we can find them by using screw pitch gauages and screw plug gauges. By using pitch gauges we can measure or check pitch value and by using the screw plug gauge we can measure or check major diameter.
Screw pitch gauges
Screw plug
Another approximation method is preparing the cast of the internal thread profile and following the same procedure as for the external threads. For preparing the cast of the internal thread, the nut is fixed in between two wooden blocks with certain gap. Through this gap molten form of metal like wax or sulphur is poured into the nut. Before pouring the molten metal, the internal thread profile should be properly cleaned and brushed from all the dust with oil. The molten metal should be poured upto a level of less than the radius of internal thread for easy removal. After solidification we have to remove the metal by lifting it up and then we should go for the measurements.
Another approximation method is preparing the cast of the internal thread profile and following the same procedure as for the external threads. For preparing the cast of the internal thread, the nut is fixed in between two wooden blocks with certain gap. Through this gap molten form of metal like wax or sulphur is poured into the nut. Before pouring the molten metal, the internal thread profile should be properly cleaned and brushed from all the dust with oil. The molten metal should be poured upto a level of less than the radius of internal thread for easy removal. After solidification we have to remove the metal by lifting it up and then we should go for the measurements.
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