Last night, the new season's Snooker German Masters qualifiers officially started. Chinese player Ding Junhui was in a hot state and won the first game, defeating his opponent Martin Gould 5-3 with a big score. In the fourth game, Xiao Ding even scored 100-0. I was so excited in front of the screen that I was itchy and called my friends to make an appointment with me one game the other day.
Of course, the protagonist we are going to discuss today is obviously not Ding Junhui, our protagonist is "beaten" - billiards. As for billiards, the ball is as its name suggests, it is round. Since it is round, the surface is not suitable for the bumpy surface. This requires roundness requirements. Today we will discuss the roundness of billiards.
9 ball queen: Let me try this ball is not round
international standard regulations:
billiard ball diameter: 52.5mm
Size tolerance: ±0.05mm
Roundness: 0.05mm
The roundness tolerance here refers to the roundness requirements for the entire spherical surface of the billiard ball.
Features to be tested: The circle passing through any section of the sphere center
Tolerance band: Tolerance band is the annular area between two concentric circles on this section, and the center of the circle is the center of the sphere
According to the above tolerance band, some friends will ask, the dimensional tolerance is ±0.05mm and the roundness tolerance is 0.05mm. Isn’t this a waste?
You may think that the ±0.05 dimensional tolerance is the radial distance between two circles. The same as the tolerance band of roundness, does it mean that the roundness is 0.05.
is not the case, because the minimum and maximum size used for comparison are measured by the two-point method, while the two concentric circles of roundness are the global cross-sectional dimensions; in addition, the inclusion principle stipulates that MMC size has a perfect shape, that is, when the maximum size of the axis, its shape cannot be allowed to exceed the 10.08 boundary.
In the figure above, with the dimension tolerance of 20±0.5, the maximum size can reach 20.5 and the minimum size is 19.5, measured by two points; for the dimensional tolerance of 1.0 (±0.5), its equivalent roundness is controlled to 1.0.
Special Note: As a 2D tolerance, multiple sections or parts of the same element must be measured to ensure that the entire length direction is within the roundness. It is usually necessary to measure each section of the workpiece twice or three times to ensure that the workpiece meets the roundness requirements.
Finally, we also wish Xiao Ding good results in the next competition and to win glory for the country!
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