Metric screws and their inferial counterparts

[mklotz]

The most important feature of this chart is the "easily confused with" column. When identifying unknown screws, these are the ones to watch. Alternatively, if converting project plans from metric to inferial or vv., these identify the closest matches in the opposing system.



Standard metric screws and their inferial counterparts

dm = diameter (mm)
pm = pitch (mm)
di = diameter (in)
pi = pitch (tpi)
tdm = tap drill size (mm)
tdi = tap drill size (in)

 dm  x  pm   (  di  x  pi )    tdm  ( tdi )  easily confused with

 1.6 x 0.35  (0.063 x 72.6)   1.25  (0.049)  [0-80 = 0.060 x 80]
 1.8 x 0.35  (0.071 x 72.6)   1.45  (0.057)  [1-72 = 0.073 x 72]
 2.0 x 0.40  (0.079 x 63.5)   1.60  (0.063)  [2-64 = 0.085 x 64]
 2.2 x 0.45  (0.087 x 56.4)   1.75  (0.069)  [2-56 = 0.085 x 56]
 2.5 x 0.45  (0.098 x 56.4)   2.05  (0.081)  [3-56 = 0.099 x 56]
 3.0 x 0.50  (0.118 x 50.8)   2.50  (0.098)  [4-48 = 0.112 x 48]
 3.5 x 0.60  (0.138 x 42.3)   2.90  (0.114)  [6-40 = 0.138 x 40]
 4.0 x 0.70  (0.157 x 36.3)   3.30  (0.130)  [8-36 = 0.164 x 36]
 4.5 x 0.75  (0.177 x 33.9)   3.75  (0.148)
 5.0 x 0.80  (0.197 x 31.8)   4.20  (0.165)  [10-32 = 0.190 x 32]
 6.0 x 1.00  (0.236 x 25.4)   5.00  (0.197)  [1/4-28 = 0.25 x 28]
 7.0 x 1.00  (0.276 x 25.4)   6.00  (0.236)
 8.0 x 1.25  (0.315 x 20.3)   6.75  (0.266)
 8.0 x 1.00  (0.315 x 25.4)   7.00  (0.276)  [5/16-24 = 0.3125 x 28]
10.0 x 1.50  (0.394 x 16.9)   8.50  (0.335)
10.0 x 1.25  (0.394 x 20.3)   8.75  (0.344)
12.0 x 1.75  (0.472 x 14.5)  10.25  (0.404)
12.0 x 1.25  (0.472 x 20.3)  10.75  (0.423)
14.0 x 2.00  (0.551 x 12.7)  12.00  (0.472)
14.0 x 1.50  (0.551 x 16.9)  12.50  (0.492)
16.0 x 2.00  (0.630 x 12.7)  14.00  (0.551)
16.0 x 1.50  (0.630 x 16.9)  14.50  (0.571)
18.0 x 2.50  (0.709 x 10.2)  15.50  (0.610)
18.0 x 1.50  (0.709 x 16.9)  16.50  (0.650)
20.0 x 2.50  (0.787 x 10.2)  17.50  (0.689)
20.0 x 1.50  (0.787 x 16.9)  18.50  (0.728)
22.0 x 2.50  (0.866 x 10.2)  19.50  (0.768)
22.0 x 1.50  (0.866 x 16.9)  20.50  (0.807)
24.0 x 3.00  (0.945 x  8.5)  21.00  (0.827)
24.0 x 2.00  (0.945 x 12.7)  22.00  (0.866)
27.0 x 3.00  (1.063 x  8.5)  24.00  (0.945)
27.0 x 2.00  (1.063 x 12.7)  25.00  (0.984)