Why are the bolts that hold steel rails together in oval holes?

It has to do with the design of the bolts. The reason that head of the bolt is oval in shape. The head of a bolt fit flush into the bar and set in opposing sets is so that a piece of dragging equipment will not shear off all the bolts in a joint but rather the just the nuts one side. As a result if the hole is not oval on one side there would be no way to tighten or loose the bolts in a joint.


Second Answer: They would be oval shapes so when contraction or expansion happens they wont snap.