Gears are the heart of all the machanical machine. They are used everywhere from cars and bikes to toys. Gears are very complex to manufacture and during manufacturing process gears do develop some errors. A single defective gear can cause probelms in machine.

Therefore, it is very important that gears must be tested properly to avoid any errors. So, in order to test the gears, the Parkinson's gear tester is used.
Let's check out the construction and working of the Parkinson's gear tester.

Parkinson's gear tester- detailed explanation |The Mechanical post


  1. The Parkinson's gear tester consists of a solid base with 2 carriages one is fixed and other is movable.
  2. These two carriages are connected together via a spring.
  3. Upon these two carriages there are 2 spindles.
  4. Upon the fixed carriage spindle the master gear is fitted.
  5. Upon the movable carriage spindle the gear to be tested would be placed.
  6. These two gears are such placed that they are in mesh with each other.( as shown in the figure).
  7. A dial indicator's plunger is in contact with the carriage. ( as show in the figure).


  1. The master gear is rotated slowly thus, the gear to be tested also rotates as both are in mesh.
  2. If any errors are present in the under test gear, it would cause the gear to move away from the centre line of the spindle.
  3. When this gear moves the carrige on which it is mounted would also moves.
  4. Now the plunger of the dial gauge indicator which is in contact with the carriage would get pressed and will show deflection.
  5. This deflection can be measured to check whether the gear must be accepted or not.
  6. Now a days there are electronic sensors are used to detect the motion of carriage instead of the dial indicator .
  7. These sensors record the motion and give an output in the form of a graph.
  8. The circular graph shows the gear is satisfactory whereas the the irregular graph shows the that the gear has errors.
Parkinson's gear tester- detailed explanation |The Mechanical post

Restrictions of the parkinson's master gear :

  1. The base of the parkinson's gear testor must be kept firm, or else this could result in incorrect readings.
  2. Composite errors only can be found out. ie. individual errors cannot be pointed out.
  3. Results of the test depends mainly on the master gear, its very important that the gear must be highly accurate.
  4. For different type of gear different master gears are required.
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