THREAD MICROMETER
1) Thread micrometer is used to measure the pitch diameter of the screw thread and it shows the variation in drunken thread.
2)It Is equal to the ordinary micrometer, it is provided with contact point.
3) It has two ends one is connected with a spindle, and another end has a fixed anvil with corresponding recess.
4) The spindle is in v-shape.
5) Both the spindle and anvil are fitted between the two thread flanks
Method of Measurement.
1. Before using the thread micrometer, we need to measure the zero.
2.with the help of contact spindle and anvil present on it we can able to measure the zero error.
3. After measuring the screw is placed between the spindle and the anvil, such that angle of point and thread flanks are in contact with the screw thread.
4.By this readings can obtain from micrometer.
5.the effective diameter of screw thread is obtained by measuring both side of major Dia and minor diameter.
6.the value obtained must be equal to the value obtain from the relation. Pitch Dia or Effective Dia = –0.6403p
Where,
P – Pitch and
D – Outer diameter.
7.the major drawback is that shows errors due to hexil angle, when it does not set to a standard guage, while start of measurement
