open-source-energy.org

here is how to make a hobbed bolt for your 3D printer


https://www.youtube.com/watch?v=WV1-N5qXTv4&list=UU5MWkMsbXeqTSQGihR0is1Q&index=2&feature=plcp

and here


https://www.youtube.com/watch?v=N0aZEXzT-m4&list=UU5MWkMsbXeqTSQGihR0is1Q&index=1&feature=plcp