Andy, I TIG welded some RR spike pieces to a 3" pipe, and then used RR spikes for the teeth of the comb.! Here is a photo of Gary’s set-up, I believe.
Looking at the second photo (the one I built), I would guess 1/8" on either side of the tooth for clearance?
Mine is hand cranked, and is located near the path from the house to the shop. I hold my breath, crank for a minute or so, and continue on to where I was going.