Here is my version of a NEMA 17 motor mount. That is the size of the stepper motors used on a MakerBot. There are several other motor mounts on Thingiverse, but none of them would work for what I had in mind. This one is designed to fit the stepper motor onto 1" X 1" (25mm X 25mm) 80/20 series 10 aluminum T-slot framing. The mounting holes will accept 1/4" (M6) size bolts - which is the size the 80/20 uses for its T-bolts.
A note about 80/20 Aluminum ( 8020.net - I have no affiliation):
If you crossed a Gilbert Erector Set with dimensional lumber (2x4, 1x6, etc.), you'd get 80/20 extruded aluminum. I'd never heard of it until I started playing with 3D printing and looked over several DIY websites which showed projects using it. Neat stuff. The 80/20 company has stocking distributors across the USA, but I'm guessing they are only interested in large orders and could care less about the DIY market. There are several web based vendors of the 80/20 parts. For me it was WAY easier to order through Amazon rather then try to figure out how to buy from any of the large raw material websites. I also see there are 1,000s of 80/20 parts being auctioned on eBay.