Screws with different thread types. From left to right
<ul><li>Metric M12, 40 mm long left turning thread</li>
<li>Metric M12, 40 mm long (ISO 4017, Strength 8.8))</li>
<li>Metric Fine M12x1.5, 40mm long</li>
<li>Metric Fine M12x1.25, 40mm long (ISO 8676, Strength 8.8)</li>
<li>United thread Standard Fine UNF 1/2 inch, 1.5 inch long (Strength Grade 5 ( ~ 8.8 ). Dimensions in metric would be 12.7mm by 38.1mm)</li>
<li>United thread Standard Coarse UNC 1/2 inch, 1.5 inch long (Strength Grade 5 ( ~ 8.8 ). Dimensions in metric would be 12.7mm by 38.1mm)</li>
<li>British Standard Whitworth BSW 1/2 inch, 1.5 inch long. (Dimensions in metric would be 12.7mm by 38.1mm)</li>
<li>British Standard Whitworth Fine BSF 1/2 inch, 1.5 inch long. (Dimensions in metric would be 12.7mm by 38.1mm)</li></ul>
All screws with hex bolt heads, although they also differ slightly in size depending on the standard. Update from <a href="//commons.wikimedia.org/wiki/File:Different_Thread_Types.jpg" title="File:Different Thread Types.jpg">File:Different Thread Types.jpg</a> with two more threads. The BSF is slightly photo shopped, since the bolt was longer
<a href="//commons.wikimedia.org/wiki/User:ChristophRoser" title="User:ChristophRoser">ChristophRoser</a>. Please credit "<i>Christoph Roser at <a rel="nofollow" class="external text" href="http://www.allaboutlean.com">AllAboutLean.com</a></i>".
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>