A system of tolerances is necessary to allow for the variations in accuracy that are bound to occur during manufacture, and still provide for interchangeability and correct function of the part.
为了允许在制造过程中必然会发生的精度变化 并提供零件的互换性和正确功能 一个公差系统是必需的。
A tolerance is the difference in a dimension in order to allow for unavoidable imperfections in workmanship. The tolerance range will depend on the accuracy of the manufacturing organisation, the machining process and the magnitude of the dimension.
公差是为了允许工艺上不可避免缺陷而存在的尺寸上的不同。公差范围取决于制造机构的精度、机加工过程和尺寸的量值。
The greater the tolerance range, the cheaper the manufacturing process. A bilateral tolerance is one where the tolerance range is disposed on both sides of the nominal dimension. A unilateral tolerance is one where the tolerance zone is on one side only of the nominal dimension, in which case the nominal dimension may form one of the limits.
公差范围越大 则制造过程的成本就越低。双向公差是在公称尺寸两侧都有公差带的公差。单向公差是仅在公称尺寸一侧有公差带的公差 在这种情况下公称尺寸成了两个极限中的一个。
Limits are the extreme dimensions of the tolerance zone. For example, nominal dimension 30mm
极限是公差带的极限尺寸。例如公称尺寸30毫米
Fits depend on the relationship between the tolerance zones of two mating parts, and may be broadly classified into a clearance fit with positive allowance, a transition fit where the allowance may be either positive or negative (clearance or interference), an interference fit where the allowance is always negative.
配合取决于两配合零件公差带之间的关系 并且可以概括地分为具有正允差的间隙配合 允差可以是正或负的过渡配合和总是负允差的过盈配合。