I needed two wingnuts for my snowblower.  I created them, then printed with a pause to insert the nut (the thread is 5/16 x 24 (If I remember correctly).  I inserted a pause just above the top of the nut.   This pause is used to insert a nut, so I can press it in, then restart the print.  

The nut is a tight fit, but it does fit.  The end result is an embedded nut in the wingnut.

Printed in PLA