Step gauge is a kind of mechanical standard artefacts of length. Compared with gauge block, its advantage is its series of aligned standard lengths of uni-direction and bi-direction.It's convenient, accurate and reliable to calibrate the continuous moving accuracy of all kinds of guide rails with step gauge.

    In figure above, L and L2 are of dimension of different direction, L1 is of dimension of same direction.
    Conventional gauge blocks are of outside dimensions, which are work surface dimensions of different directions.When we calibrate the positioning accuracy of guide rails, we need work surfaces of same directions in some cases.Empty trip and clearance exist in most mechanical structures.When guide rails move along the same directions, little impact occurs.But, if the guide rails change direction, error of direction change will occur in most cases. This includes the erro of directin change of guide rails and the erro of direction change of probes. In most cases, the erro of direction change is not necessarily a fixed value. In this case, it's very difficult to determine which part caused the erro, which causes difficulty in making correction of the guid rail.
    Step gauge has double lenghths of uni-direction and double lengths of bi-direction (inside measurement and outside measurement ). To calibrate the continuous moving accuracy of guide rails with step gauge can determine the sources of all erros and help to make correction.
    Besides, a gauge block has only one value. When continuous positions of guide rail need to be calibrated, gauge blocks of different lengths have to be used. The change of different gauge blocks costs a lot of work. Origin needs to be set and temperature needs to be the same each time a gauge block is changed, which is too troublesome. When the ambient temperature fluctuates unsatisfactorily, the reliability of calibration result will be very low. Moreove, if the work of calibration lasts long, the problem of drift of the instrument will occur.
    Step gauge has a series of values on a body, which can calibrate continuously at a time. It's convenient.fast and reliable. When calibrating CNC equipment, the calibration can be finished automatically and efficiently after the computer program is canned.