Modelling of cast disc
Mark out the edges again:

and with Scale and Shift button do as in the picture (we have to move some points there):

Repeat the previous action:

Repeat once again:

Then extrude the edges:

Apply the Symmerty modifier:

Mark out the edges again:

and with Scale and Shift button do as in the picture (we have to move some points there):

Repeat the previous action:

Repeat once again:

Then extrude the edges:

Apply the Symmerty modifier:
