Mike Hermes has been doing some great (and specific) modeling tutorials on Youtube. Recently, he has had a look into modeling various types of nuts and bolts in Maya.
There are a surprisingly wide variety of fasteners in the real world. Each poses its own challenges. Here Mike look at modeling some popular standards. These include the Hex Nut, a Cap and Acorn Nut, the Wing Nut, a Slotted Nut, and finally a common Galvanized Bolt.