The Technique of Lapping
By applying the care appropriate to any everyday position machining process, lapping can be used successfully for accuracy values within fractions of 1 micrometer (micron). Taking a 100 mm diameter as an example, the following accuracy’s are now obtainable in practice:
|Parallelism||0.005 mm||0.5 micron|
|Dimension||0.001 mm||1 micron|
|Roughness Ra||0.00001 mm||0.1 micron|
Flatness is measured with light waves. One wavelength= 0.3 my= theoretically Lambda/2 (also see Figure 69) . The other values are measured by mechanical electronic devices. The values given above as examples can be considerably improved upon if special care is taken.
For mass production however, deviations from the above values must usually be accepted, which will be due to operating conditions. In many cases inspection is performed with equipment which cannot match the accuracy of the lapping machines. The equipment should as a rule possess a measuring range lOx the tolerance range demanded.
In lapping, however, the accuracy attainable within acceptable costs is usually so good that even the most demanding workpieces are easily within tolerance.
Designers of components (workpieces) requiring fine machining should learn more about the possibilities now offered by lapping technology.