An improvised Auger

Those of us who drill really big holes by hand, 25mm (1") and up, know that a bit brace is really at its limit and an eggbeater drill is totally overwhelmed. If you are doing mortise-and tenon work on outdoor construction, the recommended mortise is something like 50mm (2") for big stuff. I need to do a woodshed; I'd like to timber-frame it. For that, 32mm (11/4") would be OK; but you need a hand-turned auger. Really what you want is a boring machine:
This is a Miller's Falls model, circa 1900. It is a geared contraption; gives you great torque, handles 50mm with ease. Unfortunately they are not made anymore; the collectibles mania (the curse of all us old-tool users) has driven the price up above $500 in most cases. So unless a boring machine drops into my lap, heaven-sent, I will have to do with a handled auger. Sometimes you can find them in antique stores; alas they are (in my experience) broken beyond repair. My only example has a blunted leadscrew. So what to do?

I have an old drill bit, 25mm, picked up somewhere for $1. Unfortunately the pyramid-shaped bit had been cut off by some insensitive person who wanted to use it in a power drill. Good luck with that -- your household drill will stall with an auger bit that large. But, like Tom Lehrer's "Lobachevsky" song goes, "Ha, ha, I hev idea!" I filed the top of the thing square, more or less. Then I stuck it in a tap handle. Metal-cutting taps are augers, after all, but they have squared shanks.
And voila, a hand turned auger real cheap! I need to find a really big tap wrench, but that is much easier to do than to find a big auger. Time for a trip to Mutant Mike's (a tool-rich and, er, eclectic thrift store). I hasten to add that "Mutant Mike's Post-Apocalyptic Junk Store" is my son's description of this valuable storehouse, and I won't identify it for fear of lawsuits.