Cannot create sketch on surface

[kmanuele]

I am trying to create a sketch in one of the roots of this gear, in order to place a hole down to the bore.

I can highlight that surface in the root but it thinks a sketch already exists there, and I can't create a new sketch. Can't create a sketch on the tooth tops either.

However, I can create a sketch on the sloped gear faces.

The gear profile was originally sourced from a manufactured component, projected onto a sketch, and new component created.

?? Ideas 

Thanks in advance

Kevin

[TheCADWhisperer]

@kmanuele 

The roots are cylindrical faces, not planar faces.

Also, many of your sketches are not fully defined?

[kmanuele · Accepted solution]

Ok. I see that. Should have done a simple measure before posting.