On Tuesday, April 12, 2016 at 9:54:16 PM UTC-7, John Doe wrote:
Using 6061 3/8" thick aluminum to hold the front sprocket on a bicycle.

A 1/2 inch square hole through 3/8 inch thick aluminum fits over the
bottom bracket square tapered spindle.

It's gonna fail. Why can't you use a proper crank with spider that takes replaceable
ring gears? The thing is, even if it took chain tension, any wobble at all
from the rotation axis is going to loosen its contact with the
square spindle.