Minolta's manual-focus SLR lens SR bayonet mount was introduced in 1958 and continued as the compatible MC and MD mounts through 1998. In 1964, Canon introduced the FL lens mount for their SLRs and continued with the compatible FD mount through 1990. Through all that, there haven't been any adapters to mount one type on the other... until now.
This adapter allows a SR/MC/MD lens to focus to infinity when used on an FL/FD body -- or, more significantly now, on an FL/FD adapter for a digital camera such as the Sony NEX models. Thus, for example, if you have a bunch of old Minolta and Canon lenses, you can use them all with an FL/FD adapter, FD Lens Turbo, etc.
Be warned that this adapter does not fully lock, although the ones I've printed are all very firm fits. Use it at your own risk. On my FD Lens Turbo, the stop-down lever is amazingly close to hitting part of the Lens Turbo, and using sr2fd.stl may interfere with normal stop down. This issue is fixed in sr2fd20130818.stl, which is 0.25mm farther away from the sensor, but still getting infinity focus. As of sr2fd20130827.stl, there is now a stationary "bump" on the adapter that essentially locks the SR/MC/MD lens on the adapter (taking advantage of the material properties of PLA), but the locking action is too aggressive with some lenses and the FL/FD/FDn side is still friction-fit. This remains a work in progress until I have incorporated a complete locking mechanism....
There are overhangs in this print, and you'll probably have to use a pair of tweezers to remove a few dropped threads and work the part on an FL/FD flange a little to get things operating smoothly, but it's really not bad. Ours were printed on a MakerGear M2 in PLA with 0.25mm extrusion and between 20%-40% fill. Use a light-blocking filament -- ideally a black that gets its color from carbon black particles rather than dye, because most synthetic dyes are transparent in the NIR band, and camera sensors will record NIR.
There are two indented holes on the part: a top one for aligning the SR/MC/MD lens and a side one for aligning with the FL/FD mount. I like to paint these red using a toothpick and a little red paint.
The photos show the SR/MC/MD->FL/FD adapter, the adapter mounting a Minolta MC Rokkor 50mm f/1.7 on a Canon FTb body, and a photo taken with that lens using my FD Lens Turbo and Sony NEX-7.
Update, Dec. 8, 2013: I've now tried printing this in MatterHacker's soft black PLA. It works very nicely printing at 230C with the bed around 80C. That material is like a very opaque hard rubber, and holds dimensions well without compressing significantly (printed at 100% fill), but the flanges and locking bump seal almost like there was a hard rubber gasket there. It seems to be a very viable alternative for this type of adapter, although the printed part is hard to get off the borosilicate bed of our MakerGear M2.