TAP SIZES

Reference B1.10-1958, R1988
American Standard for Unified Miniature Screw Threads

Representatives of Britain, Canada and the United States agreed on a standard for miniature threads in April of 1955. Unified Miniature Threads are based on the meter, and on the recommendations of the ISO regarding sizes.

Unlike larger metric taps, the designation is the major diameter of the tap, in millimeters, followed by UNM, then thread pitch. UNM thread pitch is the distance from one thread to the next thread, in mm.

Nominal Major Diameter x Pitch in Millimeters and (Approximate Threads Per Inch):

0.30 UNM x 0.080 (318)

0.35 UNM x 0.090 (282)

0.40 UNM x 0.100 (254)

0.45 UNM x 0.100 (254)

0.50 UNM x 0.125 (203)

0.55 UNM x 0.125 (203)

0.60 UNM x 0.150 (169)

0.70 UNM x 0.175 (145)

0.80 UNM x 0.200 (127)

0.90 UNM x 0.225 (113)

1.00 UNM x 0.250 (102)

1.10 UNM x 0.250 (102)

1.20 UNM x 0.250 (102)

1.30 UNM x 0.280 (90)

1.40 UNM x 0.300 (85)

1.60 UNM x 0.350 (73)

There are also many larger metric tap sizes. This list only addresses the standard UNM metric miniature taps and dies.