I need an auger that will be made of circular pieces of steel flat stock welded together. When complete the auger will be 120" long and have an OD of 36". The flights will be 3", therfore the ID of the auger will be 29". The auger will make four revolutions in it's 120" length.
I need to know what is the OD of the flat stock required to get a helix with an OD of 36" when stretched out.

Correction, the OD of the auger should be 35" not 36"