Sunday, 24 May 2020
MECHANICAL INSTRUMENTS

Types of pitch measurement methods

The types of pitch measurement methods are base on the

Pitch measurement of internal screw threads.

  1. Pitch measuring machine
  2. Tool maker’s microscope

 Pitch measurement of External screw threads

  1. Screw measuring machine
  2. Microscope method
  3. Zeiss pitch or lead measuring instrument
  4. Matrix pitch measuring machine

Pitch measuring machine

The pitch of an internal screw thread is measuring by adapter. This adapter is consists of a bar which can be placed into the ring and end of the bar, stylus is fitted with the help of a thread.

Measurement of Pitch of an Internal Thread
Measurement of Pitch of an Internal Thread

The ring gauge is held on a chuck or face plate of the machine. Which is incorporates rings up to several sizes.

In this machine a special surface plate is required with a slip gauges and dial indicator, for very large rings. And, micrometer is used to measure the movement of the stylus.

Tool maker’s microscope

Tool maker’s microscope is consists of a base with a vertical supporting column. The optical head is mounted on the column with a clamping screw, by which it can move up and down.

The screw whose elements are to be measured is placed on the table and its position is adjusted, till the intersection of cross lines seen through the eyepiece coincides with apex of angle. The reticule is rotated to bring one cross line parallel to one edge of the angle and reading is noted by viewing scale through the eyepiece.

The reticule is then again rotated to bring the same cross line to the other edge and the scale reading is taken in this position. The different between, these two readings is either the angle turned through or 360 degrees.

Screw measuring machine

Using the screw measuring machine, pitch of external screw threads can be easily measured. It consists of series of threads with non- uniform pitch. The pitch is the one which aligns perfectly with thread being tested. Therefore, the accuracy of measurement is based on sighting method.