When do diamondback rattlesnakes develop rattles?

Rattlesnakes are born with an appendage called a button and the first section of what is to become the rattle, of course the rattle will not make any noise until a few segments are asdded. These segments which interlock loosely with each other are added each time the snake sheds its skin and they will shed 3 or 4 times a year depending on the area they live in. The interlocking looseness of these segments is what causes the rattling noise when the snake vibrates muscles in its tail>