Just another M3 Thumbwheel!

So, I wanted to make it easier to level my print bed (Mendel Prusa, mounted on 4 x M3 bolts with springs), and the obvious answer was to install thumbwheels to make it easier to adjust each levelling screw quickly and easily. Sure, I could have just downloaded someone else’s design like this http://www.thingiverse.com/thing:13807 or this http://www.thingiverse.com/thing:5246 or this http://www.thingiverse.com/thing:13065 – but where’s the fun in that? Far more satisfying to design and pri