Coach bolts generally/always have a square section under the head. This is to grip the wood and to resist loosening.
Is it possible to get coach bolts without this square section? May be they're called something else. I still want the shallow domed head of the normal coach bolt - no screwdriver slot. These are for a restoration project. The bolts go through a steel bracket then through about 80mm of oak then through another steel section. Finally the nut goes on (no washer). Of course the square section will stop when it reaches the steel bracket so leaving a small gap under the head.
This may not be the ideal way to make the fixing but it is a restoration and I would like to do it to the original. I could file a square opening in the steel bracket or file off the square section if I had to.
And I guess any modern coach bolt would be zinc plated. The originals were just a natural black finish.
Thanks