花岗石方箱的主要用途：是测量工件的平行度、垂直度和划线时支撑工件。一般为边长相同的正方体或长方体 。
    花岗石方箱系列精度等级度
    规格精度等级Grade
    Dimension平行度平面度垂直度
    mmParallelism of working surfaceFlatness of working surfacePerpendicularity of working surface
    50*50*500.0020.0010.0020.0010.0010.0005
    100*100*1000.0020.0010.0020.0010.0020.001
    150*150*1500.0030.00150.0020.0010.0030.0015
    200*200*2000.0040.0020.0030.00150.0040.002
    300*300*3000.0060.0030.0030.00150.0060.003
    400*400*4000.0080.0040.0040.0020.0080.004
    500*500*5000.010.0050.0050.00250.010.005
    600*600*6000.0120.0060.0060.0030.0120.006