hey there Robin,

to make the bumps it's as simple as grouping one set of knobbles (select them then ctrl & g) then, with the group selected, open the Edit > Duplicate Special atributes, set the y rotation to equally distribute the number of knobble groups you need around the edge (I kept it simple and set it to 1 degree in order that there would be 360 sets of knobbles). Next set the number of copies to 1 less than the amount you need (remember that you already have one copy) so in my case it would be 359 and hit the Duplicate Special button.

I'm assuming that the platter is central to the world co-ordinates, if it's not then snap the group pivot to the it's centre before you duplicate. Also if you're version of Maya is earlier than 8 there is no Duplicate Special option, everything is under the Duplicate attributes.

I hope that helps,

Mat