ISO 21940-32:2012规定了一种平衡键转子组件单个部件（轴和配件）的惯例。这提供了所有平衡部件的兼容性，以便在组装时满足转子组件的整体平衡公差和/或振动极限。 ISO 21940-32:2012规定，在平衡带键转子组件的单个部件时，应使用半键。它还规定了根据使用的关键惯例平衡的部件的标记。 ISO 21940-32:2012适用于在平衡机中、在其自身轴承中或在现场进行平衡的转子。当测量带有键槽但尚未装配配件的转子的剩余不平衡量和/或振动时，也可以使用键约定。 除了适用于恒定矩形或方形交叉键- 平行于轴中心线安装的部分，ISO 21940-32:2012也适用于安装在锥形轴表面上的键，适用于半圆键、钩头键、定位销和其他特殊键。半键约定的原则适用于特殊键的特定形状和位置。

ISO 21940-32:2012 specifies one convention for balancing the individual components (shaft and fitments) of a keyed rotor assembly. This provides compatibility of all balanced components so that when they have been assembled the overall balance tolerance and/or vibration limit for the rotor assembly is met. ISO 21940-32:2012 specifies that half-keys be used when balancing the individual components of a keyed rotor assembly. It also specifies a marking of the components balanced in accordance with the key convention used. ISO 21940-32:2012 applies to rotors balanced in a balancing machine, in their own bearings or in situ. The key convention can also be applied when measuring the residual unbalance and/or vibration of rotors with keyways, but to which fitments have not yet been assembled. In addition to applying to keys of constant rectangular or square cross-section mounted parallel to the shaft centreline, ISO 21940-32:2012 also applies to keys mounted on tapered shaft surfaces, to woodruff, gibhead, dowel and other special keys. The principle of the half-key convention is applied as is appropriate to the particular shape and location of the special key.