Firstly, we must determine the wear degree of the guide surface of mechanical equipment, and we must check the accuracy of the guide surface. The basic accuracy of the guide mainly includes the straightness error in the vertical plane, the straightness error in the horizontal plane and the parallelism error in the vertical plane. Straightness errors of guideways in vertical and horizontal planes and parallelism errors of two guideways in vertical planes directly affect the geometric accuracy of the machined parts. Straightness errors of guideways in vertical planes are the basis of various accuracy of mechanical equipment, and the magnitude of their errors determines the fluctuating state of the slide in motion and the state of the slide and guide. Contact of rail.

　　测量导轨直线度误差的基本原则：

　　Basic Principles for Measuring Straightness Errors of Guideways:

　　（1）直线度误差的测量基准可以任意选择，而评定基准应符合较小条件的原则。这就是说，测量导轨精度时，必须用两条平行的理想直线包容住被测导轨的实际轮廓，并使此理想直线间的距高为较小。则这两条被称为导轨包容线的理想直线间的距离，就是被测导轨的直线度误差。

　　(1) The measurement datum of straightness error can be chosen arbitrarily, and the evaluation datum should conform to the principle of minimum condition. That is to say, when measuring the accuracy of the guideway, two parallel ideal straight lines must be used to contain the actual outline of the guideway under test and to minimize the distance between the ideal straight lines. Then the distance between the two ideal straight lines, which are called the inclusive line of the guideway, is the straightness error of the guideway under test.

　　（2）无论评定基准怎样转换发明奖计量方向始终不变的原则。这个原则是测量读数所反映的计量方向始终应垂直于测量基准，采用两包容线之间的坐标距离计量，不应因评定基准发生转换，造成评定基准之间产生微小倾斜而改变方向。

　　(2) No matter how the benchmark is changed, the measurement direction of the invention award remains unchanged. This principle is that the measurement direction reflected by the measurement readings should always be perpendicular to the measurement datum. The coordinate distance between the two containment lines should not be used to measure the direction because of the conversion of the evaluation datum, resulting in a slight tilt between the evaluation datum.
                            

　　（3）对导轨只做等节距的若干档后，用水平仪或者其他精密测角仪器借助专用桥板，使其支撑点首尾相接，沿测量方向移动，分别测量出各档相对水平仪上，所选定的零位（测量基准，为水平线）的倾斜角。从而就可换算成相邻间的高度差。各等距有限点间相对高度差值的综合结果就体现了被测导轨的曲线的起伏变化状况，用水平仪进行等节距有限点测量导轨的技巧了。

　　(3) After only making several equal pitches for the guide rail, the supporting points of the guide rail are connected head to tail with the help of a special bridge plate and move along the measuring direction. The inclination angles of the selected zeros (measuring datum, horizontal line) on the relative levelers of each gear are measured separately. Thus, the height difference between adjacent areas can be converted. The comprehensive results of the relative height difference between the finite points of equal pitch reflect the fluctuation of the curve of the guideway under test. The technique of measuring the guideway at the finite points of equal pitch with the level instrument is introduced.