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6 Steps -- How to Select a Gage Block Set

1)  Decide which system of measurement (inch or metric) is most appropriate.

2)  Determine the range of measurements that might be made from the desired set.
     Break down the measurements into ranges that are frequently made and
     infrequently made.

3)  Determine the "comfortable range" of a set. (Click here to expand this choice.)

4)  Choose a style of block:  (Rectangular, Square, or Heavy Duty).  Note:  The choice of
    style may restrict the choice of material and grades.  (Click here to expand this choice.)

5) Choose a gage block material.  (Click here to expand this choice.)

6) Choose an accuracy grade.    Note:  Certain accuracy grades may not be available in all
    materials or styles.  (Click here to contract this choice.)

A.  Grade 0, Webber A1:  The most popular grade of blocks:   
        1)  it is accurate enough to perform 95% or more of all applications.   This grade is recommended for general
             use.
        2)  most steel blocks are Grade 0, and steel is the most popular choice of gage block materials.

        Most gage blocks are used to check micrometers and calipers.   Assuming a micrometer needs to be calibrated
        to an accuracy of .0001".   If the 4:1 accuracy ratio rule would apply, then grade 0 gage blocks must have a
        tolerance of not less than ±.000025µin.  In fact, the tolerance (up through 1 inch) is ±.000005.  Thus, in this
        application, grade 0 gage blocks are 5 times more accurate than needed.

B.  Grade 00, Webber AA:  These blocks are to be used as laboratory references or to calibrate gage blocks
       with lower accuracy grades.   It would be very unusual to use grade 00 blocks on the shop floor.  The accuracy
       of measurement is only slightly improved over grade 0 tolerances, but at a much higher cost.  This additional
       cost is usually only justified when reducing measurement uncertainties is absolutely required.   Available from
       Webber in the croblox®  or ceramic materials.  Not available in steel.

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GB59