Mounting idler pulleys on your own design and build 3D printer can be difficult because of the narrow bearings that are often used. When Andrew at +3DprintedLife called out to the community for ideas on how to solve this issue for his upcoming Eclips3d2, I realised I was going to have the same problem in my new printer design, so set about testing various bits of hardware to find a good way of mounting M3 idler pulleys.

This video is a summary of my findings and opinions. The printer isn't built yet so there's no proof I've made the right decision. My conclusions might be applicable to M4 and M5 idler pulleys but I haven't tested with those sizes. I also realise I didn't include countersunk bolts/screws in my comparison - they would probably be very good in this application and I do plan to get some for my new printer.

I also tried drilling out the centre of some brass M2.5 washers but the drill bit "bit" and deformed the stack of washers. If someone else has more skill, this might work (Dremel grind the centre out?).

Links to the Harwin 5mm round spacers: http://uk.farnell.com/harwin/r30-6200... and rivnuts: STEEL, ALUMINIUM & STAINLESS RIVNUTS NUTSERTS RIVET NUTS M3 M4 M5 M6 M8 M10 M12 http://r.ebay.com/eZoZxO.