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.

　　測量導軌直線度誤差的基本原則：

　　Basic Principles for Measuring Straightness Errors of Guideways:

　　（1）直線度誤差的測量基準可以任意選擇，而評定基準應符合較小條件的原則。這就是說，測量導軌精度時，必須用兩條平行的理想直線包容住被測導軌的實際輪廓，并使此理想直線間的距高為較小。則這兩條被稱為導軌包容線的理想直線間的距離，就是被測導軌的直線度誤差。

　　(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）無論評定基準怎樣轉換發明獎計量方向始終不變的原則。這個原則是測量讀數所反映的計量方向始終應垂直于測量基準，采用兩包容線之間的坐標距離計量，不應因評定基準發生轉換，造成評定基準之間產生微小傾斜而改變方向。

　　(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）對導軌只做等節距的若干檔后，用水平儀或者其他精密測角儀器借助專用橋板，使其支撐點首尾相接，沿測量方向移動，分別測量出各檔相對水平儀上，所選定的零位（測量基準，為水平線）的傾斜角。從而就可換算成相鄰間的高度差。各等距有限點間相對高度差值的綜合結果就體現了被測導軌的曲線的起伏變化狀況，用水平儀進行等節距有限點測量導軌的技巧了。

　　(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.