As the factors which make difference between theoretical tightness of fit and actual one, the authors study effect of out of cylinderness of axial profiles of shaft and ring on tightness, ratio of contact, etc. in this report.
In order to express skewness of cylinder of the parts, they use radial length of "overlap" of both skew cylinders with same mean cylinder.
As the results of experiments, we have found the followings:
1. Actual tightness varies according to difference of "overlap" even if they have equal mean interference.
2. Even if fitting surface is locally missed, tightness does not become so loose.
3. In case that both roundness and cylinderness of each part are wrong, tightness becomes easily loose by repeating disassembling and assembling, compared to the case that only cylinderness is wrong.
4. As ratio of contact is unexpectedly small, wearing, stick slip may be easily caused at the contacting points.
Therefore attention must be given to lubrication of fitting surface.