According to its definition, the measurement of ellipticity is the difference between the maximum and minimum diameters on the cross section of a cylindrical surface.
Therefore, it basically belongs to the diameter method, and any method of measuring diameter can be used to measure ovality, that is, after measuring its maximum and minimum diameters respectively, the difference is calculated, which is the value of ovality.
In the specific measurement, it is obvious that the method of measuring its fluctuation can also be adopted, that is, under the contact of micrometer, the workpiece rotates on the flat plate once, and the difference between its maximum and minimum indication is taken as its ellipticity. It can also be measured by pneumatic differential method, and its rotation angle can be less than 90.
Besides the diameter method, the ovality can also be measured by the radius method. For example, a workpiece with a central hole can be measured by the radius method (pushing the workpiece between centers), but the eccentricity of the center will affect the workpiece.
It can also be measured on a roundness meter, but the radial difference is measured, so the actual ovality should be multiplied by 2 times? .
Extended data:
The cause of ellipticity
After honing, parts sometimes appear ellipticity. There are many reasons for ellipticity:
1. The ellipse generated in the previous honing process is too large to be corrected after honing.
2. The allowance left by honing is too large, and the transverse feed during honing is too large, resulting in high cutting temperature. Coupled with poor cooling conditions, the heat on the surface of the parts cannot be dissipated, resulting in local deformation and ellipticity.
3. Uneven hardness of oilstone and different wear conditions lead to uneven surface of parts, or improper adjustment of oilstone leads to ellipticity.
4. Improper fixture design, or excessive clamping force, especially for thin-walled parts, leads to deformation and ellipticity after honing.
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