Bolt used for fastening connecting rod caps
The con rod cap bolts must be subject to at least two screwing operations during the productive cycle of the engine and must therefore be engineered to guarantee a more constant distribution of the axial load.
In designing them, the double tightening strategy which they are subjected to during machining and assembly must be carefully analyzed.
In almost all cases they have a 10.9 strength rating and increasingly more a 12.9 rating. They are more and more designed with custom strength ratings, even with very narrow Rm ranges.
They work in the plastic range and are usually tightened based on torque + rotation, they have an external driver head, almost never require a washer. In most cases they are phosphated and oiled.