How to use CFrame rotation along a fixed part?

local firebrick = game.workspace.WaitForChild("firepart")
local pivot = game.workspace.WaitForChild("pivotbrick")

local pivotposition = pivot.Position

while true do
	firebrick.CFrame = CFrame.new(pivotposition) * CFrame.Angles(0, math.rad(i), 0) * CFrame.new(-42.5,0,0)
	wait()
end

Here is what I have tried for rotating a part via CFrame.

Pre-made CFrames include the rotation automatically.

Get the CFrame of “pivot” and set “firepart” ‘s CFrame as that.

This should copy the exactly position and rotation of “pivot” ‘s