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Carbide balls Grade 25 AFBMA with tolerance of ±.0001" and sphericity of .000025" are mounted on short shafts whose length = L and diameter shown in the chart below. American made.
Among other things, fractional contact points are ideally suited to measure small diameters or width of grooves. Some mathematical computation may be required.
GIROD-TAST
The "other" Swiss indicator still made in Switzerland.