一般的螺距计是带有特殊附件的测微表(见图1)。附件是两个可伸入螺纹凹槽中的球体测头,其中一个是固定测头,另一个为活动测头,后者经杠杆系统与测微表相连。这种螺距计在使用时有两个缺点:(1)操作不便。由于它只能以固定测头2做靠山,由活动测1头进行测量,故要准确定位相当困难。当重复测量同一螺距时,往往由于放置螺距计有上下左右的偏斜而使每次读数不相同。(2)测量误差较大。我们知道:“恒定的测量压力”是进行精密测量的一个很重要条件,而这种螺距计在使用时将固定测头推向工件的一面,这种推力不可 The general pitch gauge is a micrometer with a special attachment (see Figure 1). The attachment is two ball probes that extend into the thread groove, one of which is a fixed probe and the other an active probe, which is connected to the micrometer via a lever system. This pitch meter in use has two shortcomings: (1) inconvenient operation. Because it can only do a touch with a fixed probe 2, measured by the activity of a head, it is very difficult to accurately locate. When repeated measurement of the same pitch, often due to the placement of the pitch gauge up and down about the deflection so that each reading is not the same. (2) measurement error is larger. We know that “constant measurement pressure” is a very important condition for precision measurement, and this type of pitch gauge will be used in the fixed probe to the side of the workpiece, this thrust can not