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在用比较测量法测量工件时,首先遇到的问题是,如何正确地选择比较测量的基准件,因为基准件的精度将直接反映到测量结果,它是保证测量精度的主要关键。而内径百分表多数采用四点定位测量,由于其结构和读数误差的影响,所以,精度不高。例如:当以五等三级量块为基准件,用一级百分表作读数机构时,也有16微米至20微米的测量方法极限误差。到目前为止,绝大多数中、小工厂,选用量具十分混乱,在测量孔径尺寸时,不论产品公差值大小,习惯用外径千分尺作为基准件,来校对内径百分表的测量尺
The first problem encountered when using a comparative measurement to measure a workpiece is how to select the base of the comparative measurement correctly because the accuracy of the base will be directly reflected in the measurement, which is the key to ensure the accuracy of the measurement. The internal diameter dial indicator with four-point positioning most of the measurement, due to its structure and the impact of reading errors, so the accuracy is not high. For example, when using a first-class dial gauge as a reference unit and a first-order dial gauge as a reading mechanism, there is a limit error of the measurement method of 16 μm to 20 μm. So far, the vast majority of small factories, the selection of measuring tools is very confusing, in the measurement of aperture size, regardless of the size of the product tolerance, accustomed to using an outer diameter micrometer as a benchmark to calibrate the gauge dial gauge