7 CFR § 51.2660 - Metric conversion table.

Inches	Millimeters (mm)
8/64 equals	3.2
16/64 equals	6.4
24/64 equals	9.5
32/64 equals	12.7
40/64 equals	15.9
48/64 equals	19.1
51/64 equals	20.2
52/64 equals	20.6
54/64 equals	21.4
56/64 equals	22.2
1 equals	25.4
1 8/64 equals	28.6
1 16/64 equals	31.8
1 24/64 equals	34.9