The cogs are salvaged from an old photocopier. I realise the smaller cog has typically less teeth in other designs but we'll see how this one goes! The stepper motor is from an old 5.25" floppy drive!
The bearing recesses were achieved by clamping the two 15mm blocks together and drilling a hole 22mm diameter with a flat wood bit to a dept equal to the bearing width, so the bearing would recess until flush with the edge. These recesses hold the bearing snugly in either side of the block.
Here you can see the bearing mounting block for the filament drive shaft, and it's partner, the idle pressure bearing (smaller bearing pinned into the second block.)
Wade Extruder instructions. I've used 6mm steel shaft. I cut it to the desired length and threaded both ends and am using M6 nylock nuts on either end. The skateboard bearings came with sleeves which reduce the bearing centers to 6mm, normally an 8mm hole. I'm pinning the large cog wheel with a small bolt through a hole drilled through the shaft.
Thanks for viewing. Comments and questions welcome.