I like to ground a motor direct to its frame, even if i have to drill/tap a hole. But in The NEC codebook, its grounded if it's part of a complete assembly (a machine). Did you look in the terminal box carefully?
I tried it but found it difficult to heat the piece enough (on a large piece). I soldered 2 1" round tubes in a 'T' and it held good until it got a good hit and broke. All in all, i wouldnt use it on a job.
The aerodrome is cool. There's a great steel supplier in poughkeepsie! Dutchess Metals. There's also a very cool machine shop next door. How about Orange County Choppers in Montgomery? Just a hop over the Newburg bridge.