Question Fan screw diameter and thread pitch?

You would think this would be an easily answered question, but I can't find the answer anywhere!

Apparently I have two different fan screws with two different thread pitches.

I know one is 5mm diameter, with a T16 pitch. The other is 4.9mm with a T14 pitch.

What does T16 and T14 actually mean? And which one is "standard"?
 

tennis2

Dignified
Not sure why they're labeled with a T prefix. But threads are typically represented as threads per inch. In metric, it's distance (mm) between threads (measure peak to peak). 14-16mm between thread peaks isn't right though for those screws.

I also thought that metric was 5mm, 4mm, 3.5mm, 3mm, etc etc. 4.9mm seems strange.
 

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