Originally Posted by Pablo
Acorn nuts are junk. Use them in your next concrete pour.
Acorn, or cap, nuts have been around for a long time. I certainly hope they aren't junk! Motorcycles, autos, aircraft, all use acorn nuts. Acorn nuts aren't different...they simply have a closed crown that covers the exposed end of the threads.
They are used to:
1) To protect the threads from damage/corrosion/dirt.
2) To protect skin from the sharp exposed threads.
3) To create a clean, finished, appearance.
The problem comes from the length of the threaded portion that the nut engages. Obviously if the stud length is not correct, the Acorn nut will bottom out before it clamps the mating parts.
I'll agree that, (for most MB'ers), it's easier to replace the acorn nuts with standard hex nuts as opposed to correcting the length of the stud.