creating threads using revolve" in "Design Spark Mechanical"- base cilinder diameter for the bolt = 12,5 mm- inside cilinder diameter used for the nut = 13 mm- placed the faces used for the thread cutting 0,5mm "inside" the base cilender (did not use the complete face), you'll find the used faces in the DesignSpark file (the smallest is used for the bolt, the biggest for the nut, to get some additional marging.- I think normal metric thread has a 30 degree angle, but I used 45 degrees for better printability.This is where I learned how to do it ....http://www.rs-online.com/designspark/electronics/eng/knowledge-item/designspark-mechanical-thread-creation