Development work

I've drilled all the holes for the frames of the other stages now - only the extruder and bearing arm mounts still to do. When positioning the frame onto a stage, it was easiest to make the frame and then mark through the frame's holes onto the MDF.

I have also started design/development work on the bearing-substitutes and the required positions for the pivot arms with the springs that I have (not 4 ").

I have had a lot of difficulty with the little pins that hold the springs - they twist around in use and the spring slips off. I think it is because the MDF (unlike acrylic) gives a little. I am going to try bending the pin right over to prevent this happening. If my pins are long enough.

I went back to B&Q yesterday - they have lots of countersunk bolts of all different diameters and lengths, in packs of 10 including nuts. These are not labelled/found on the website under countersunk/countersink.
When I have worked out exactly which bits I'm using, I'll put the relevant parts and costings up.

For cutting the PTFE rod, I used masking tape to mark the location of the cuts. This also prevented any skating of the saw from damaging the round surface of the rod, which will be essential to act as low-friction "wheels". In order to drill a central hole, I made a little box of glued-together MDF (the same width as the diameter of the rod and approx the same height as the disks I'm cutting), which enables me to mark the centre of the circle (across the diagonals of the box) very easily, using the disk in one orientation and then in a second orientation 45 degrees from the first. (Perhaps a photo' and/or diagram would help here....)
I used a centre punch, then 1.5, 3.5 and finally 5.5 mm drill bits for my centre hole in the PTFE. The holes were pretty darn close to central. I'm now thinking of marking the centre of the box and drilling a marking hole through that - I may even be able to drill a disk through it if I can find a way of holding the disk so it doesn't just spin with the drill bit....