Screw Identification

[ADT]

This seems to be one of those "am I the only guy who doesn't know this" questions.
I've tried quite hard to locate an explanation behind the 'code' which identifies screws, in particular TEKS types, those self drilling ones.
For example a teks screw can be described as 14-20x22 plus a few other identifiers. Now I know that the last number is the grip length in millimeters (underside of head to point), but I can't find any reference to tell me the other numbers. One of them will be the gauge; the other is either the pitch of the threads or a 'type' number.
Can anyone help me with a lead on this?

Anthony Tugwell
Project Director & Consulting Engineer - now in Australia

 

[deanc]

http://www.jamesglen.com.au/

Go to the "training Manual".

 

[deanc]

http://gltrs.grc.nasa.gov/cgi-bin/GLTRS/browse.pl?1990/RP-1228.html

Here is another for you. Gift of the American taxpayer( I don't mind things like this)