It's just that all the way thru the DVD he refers to Pi as 3.1461 and not 3.1416.
Pi is used a lot in gearcutting and all his references are to the fomer number making all his calculations incorrect.
Didn't count but was probably a total of 12 times.
Also when hobbing a gear he tilts the dividing head to the helix angle of the hob.
this is incorrect and will not compensate but just cut a wider tooth form than is correct for the size.
Probably makes up for Mexiacn Pi