"Peter H." wrote:


... it could be 82 and 90 degrees, or it could be some other number ...


Countersinks are made in 60, 82 and 90 degrees.

Machine screws are 82 degrees.

Specialty screws could be 90 degrees.

There are also 100 deg flat head screws. I've used them. In sheat metal
they are quite usefull. ( I have only used #6 and #8 I believe)
...lew...