I've done some more work on the extruder build. I had some problems getting the gears to mesh correctly, I found that the large gear seemed to be slightly ovalised which meant that as it turned the wheel would grind in some places and miss in others. I think I have solved this by filing down the teeth that were grinding using a triangular file (note the red marks I have put on so I know where to file) until eventually the gear wheel was circular. It's still not perfect but should be workable I think. I still need to glue the nozzle assembly in place.
I have also starting working on the x-axis. Beginning with the x-carriage. Nothing too difficult here except the captive nuts. A few of the nut locations had to be drilled to the correct shape to hold the nut, I did this using my dremmel clone with a small drill bit and file attachments, time consuming but works in the end. It is also important to remember which holes have to be drilled at an angle.