The effect of elastic deformation of inside micrometers on the accuracy of measuring large internal dimensions

Conclusions

• 1. The measuring error due to elastic deformation of inside micrometers is less when they are used in the horizontal position compared to the vertical position.

• 2. The errors are negligibly small for inside micrometers of the cylindrical tubular and assembled types when used in the horizontal position and also for cigar-shaped micrometers up to 8000 mm length used in any position.

• 3. The error of assembled inside micrometers used in the vertical position depends on the location of the micrometer head. The compression and corresponding reduction in length of the measuring rod is considerably greater when the micrometer head is at the top compared to the case when the head is at the bottom. If the micrometer head is at the bottom, the error is negligible when measuring parts made to Class-2 (USSR Standard) or opener tolerances.

• 4. Adjustable inside micrometers of size greater than 2500 mm have low rigidity when the inner tube is extended and deflect considerably. The error can reach 100μ if the micrometer length is 4000 mm and it is used in the vertical position (see Table 1). The same error can occur if the micrometer is used in the horizontal position provided the points of support during inspection and actual measurement are not identical.