Fine grinding and super fine
grinding are the final processing procedures of
steel balls. Super fine
 grinding procedures are
generally used for the processing of steel balls
higher than G100. The final dimensional deviation,
geometric accuracy, surface roughness, surface
quality, burn and other technical requirements of
the steel ball shall meet the provisions of the
process specification of fine grinding or super fine
grinding process.
When checking the diameter deviation and geometric
accuracy of the steel ball, it must be measured on
the specified special instrument. The surface
roughness and surface quality of the workpiece after
fine grinding are generally inspected by visual
inspection under the astigmatism lamp. In case of
dispute, it can be checked under a 90x magnifying
glass and compared with the corresponding standard
photos. For the inspection of workpiece surface
quality and surface roughness after superfinishing,
a certain number of workpieces must be selected and
compared with standard photos under a 90 times
magnifying glass. When the surface roughness is in
doubt visually, it can be tested on the surface
roughness instrument.
The burn examination methods of fine grinding and
super fine grinding shall adopt random sampling, and
the quantity and quality standards of sampling shall
comply with the provisions of burn standards.
The reasons for poor surface roughness are:
1. The processing quantity is too small and the
processing time is too short.
2. The groove of the grinding disc is too shallow
and the contact surface between the groove and the
workpiece is too small.
3. The hardness of the grinding disc is too high or
uneven, and there are trachoma and pores.
4. Too much grinding paste is added, or the abrasive
particles are too coarse.
5. The grinding plate groove is too dirty and there
are iron filings or other sundries.
The reasons for poor local surface roughness are:
the groove of rotating grinding disc is too shallow
and the contact area of workpiece is too small; The
angle of the grinding disc groove is too small to
make the workpiece rotate flexibly; The pressure
applied by the upper grinding plate is too small,
resulting in sliding between the workpiece and the
grinding plate.
Grinding damage on the surface is also a defect,
which often occurs in cyclic processing. In severe
cases, pits with a certain depth can be clearly seen
under the astigmatic lamp. Only a black or yellow
can be seen under the slight astigmatism lamp.
However, pits can be seen under a 90x magnifying
glass, with rough low parts and staggered scratches.
The causes are: the depth of the grinding disc
groove is different, and the workpiece sometimes
stays and slides in the deeper groove due to low
pressure, resulting in the grinding injury at the
contact between the workpiece and the grinding disc;
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