Rotating model script problem?

I am working on a CFraming script that will rotate a model, but it is not working very swell (Rotate, but go away from each other).

model = game.Workspace.Model


children = model:GetChildren()
for i = 1, #children do
local CFPos = children[i].Position --gets current position of each block
	children[i].CFrame = CFrame.new(CFPos) *CFrame.Angles(0,0,.5) -- keeps block in position and rotates
end