Assignment

The measuring of the cylinder diameter leads to a more exact analysis of the state of wear and tear. In this case, one can decide which repair possibilities are open, or whether a repair must take place at all. Apart from the pure measuring, a visual examination is also important. The eveness of the cylinder and its sealing surface can be checked with a straight-edge ruler.

Function

In the above picture, one can see how an inside micrometer is brought into position to correctly determine the diameter. Important requirements:

-	The instrument must be held vertical, so that a higher value is not shown.
-	The highest wear is to be expected a little below TDC.
-	It should be measured at about 90° to the longitudinal direction.

The calibration of the micrometer is particularly important. Measuring plates of an exact length are placed into a test-plate holder, In such a way as to allow an exactly defined gap. The micrometer can then be placed into this gap to set the baseline value. The piston-play varies greatly according to temperature and the measuring direction. In a cold state, and at 90° to the pin direction, it amounts to roughly 0,04 mm. 02/11

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