No other info is provided.
This is a top view of the part.
Here's the link to the full blueprint: http://library.centerofthewest.org/digital/collection/WRAC/id/2777/rec/8932
It also has other calls for lead of helix cuts. Also the same call is used in another place of the blueprint. Maybe the 7/16" cutter should be used for it, not sure.
In CAD, would one use a helix to cut from top to bottom?
Or to cut from back to front (direction of face normal)?