root dimension Odd tooth gears

[rinkman11]

I am told the root is called a chord and I am also told the root is called a diameter
I believe it is a chordal dimension and the true diameter would need a multiplier to be called a diameter

 

[3DDave]

One can make either a chordal measurement for tooth thickness or tooth gap or make an arc measurement; chordal thickness/wdith is far easier. It is unfamiliar to me to call anything having to do with the root a chord.

The root is also associated with a diameter. For an odd-numbered toothed gear one typically makes a correction when the measurement is to be made with calipers.

I would suggest reading MIL-HBK-400, found at

https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=54028