Both UNF bolts and Metric bolts are offically identifed by the diameter of their shanks.
The table below gives the imperial name (e.g 1/4) the reading you should get on your imperial micrometer and it's metric equivilent in mm
Imperial Fractional mm
1/8 0.125 3.175
3/16 0.1875 4.7625
1/4 0.25 6.35
5/16 0.3125 7.9375
3/8 0.375 9.525
7/16 0.4375 11.1125
1/2 0.5 12.7
9/16 0.5625 14.2875
5/8 0.625 15.875
11/16 0.6875 17.4625
3/4 0.75 19.05
13/16 0.8125 20.6375
7/8 0.875 22.225
15/16 0.9375 23.8125
1 1 25.4
Sorry about the odd formatting, the sapces between the columns seem to have been reduced to a single space
Last edited by Chris Cussen; 26th March 2010 at 08:11..
Reason: Apology
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