Countersunk Holes and Implied 90 3

[engAlright]

Section 1.8.12 of Y14.5-2009 indicates that for countersunk holes "...the diameter and included angle of the countersink are specified.".

In the corresponding figure 1-39 the countersink feature is shown dimensioned with a 90° angle.

Why is an angle dimension required when the included angle is 90°? Would an implied 90° angle (section 1.4i) not apply? This is the only instance I can think of where a 90° angle needs to be shown on the drawing.

Thanks!

 

[engAlright]

Well seems like I'm in the minority...consensus seems to be that showing the angle is the way to go. It still seems weird to show a 90° angle dimension on a drawing but I understand that the tendency will be to assume the Engineer has forgotten to add a dimension, rather than assuming an implied 90 applies.

And for reference ANSI metric countersink angles are 90°.