What is the diamond shape in a circular saw blade for?

[Frank]

I noticed all circular saw blades have a diamond pattern around the hole in the middle. I am guessing this is to prevent warpage as it heats up or is there some kind of saw that uses a shaft of that shape?

Yeah, I know my hand tools, but this one i wasnt too sure about

[wrenchguy]

old power saws had a matching diamond arbor to clinch the blade while in rotation, later its been determined that compression by heavy washer and bolt would work.
good luck.

[Aunt Phil]

Skill worm drive saws used the diamond.