Add a Perpendicular Constraint
Add to the 3D Sketch the Perpendicular Constraint to the two part. You can use the cylinder and cone faces, also the straight lines.
- On the  tab, in the Constraints group, click tab, in the Constraints group, click Perpendicular. Perpendicular.
- Select the point or the line from the 3D sketch.
- Select from the 3D sketch the line you add the constraint.
- Select Confirm.
Note: 
  - You can delete the Coincident constraint from the constraint list.
