[Psychotechnoid]

Oh - I had the cross section messed up. Actually, the sprockets are 3/4" wide, and there are two of them, so that's a total of 1.5" of key stock. 3/32" * 1.5" = 0.140625" and 1920 / 0.140625 = ~13,653.3 psi. Or should I only take one sprocket into account at .75" for a pressure of ~27,306.7 psi? In any case, 3/32" * 1/2" = ~0.047, not 0.0047, so your calculated pressure for 1/2" long keys would be ~40,000 psi, not ~400,000 psi. Are any of those numbers workable, or are they still excessive?

Edit: and yes, we could definitely bolt the sprockets together - that seems like a good idea given the situation.