These are some of the default nuts and bolts from the Bolts user preference in Blender. You can use preset metric sizes, change the bit type to Phillips, hex or none, you can set the head to: countersink, pan, dome cap, hex; you can set the: head diameter, shank length, shank diameter, Major diameter, Minor diameter, Pitch, Crest Percent and Root Percent.
I understand that there is a clash detection tool on the Mechanical Blender fork project. Also, in regular Blender there are many new pre-made shapes that will be of great help to the mechanical and HVAC specialties. Also, some of the new bevel and shaping tools in Blender 2.8 (currently in beta) now lead the industry in innovation and usefulness, and most importantly they are time-saving.