E3D is selling very high quality Gates idlers. However, the idlers are wider and have a different inner diameter than the commonly available idlers used on Prusa printers. User tetra3dprint had a great idea to modify the Bear X-axis idler mount to allow use of one of these E3D/Gates 20T idlers. His design uses an adapter to allow those currently using the smaller idlers to re-use whatever they are using for the idler axle (typically, a dowel pin).
My design does away with the adapter. You would need to source a suitable axle. Here are some options:
- 4.95mm drill rod from McMaster Carr, cut to length ( https://www.mcmaster.com/2900a299 )
- "Go plug gauge", cut to length, These have a very precise diameter, so you can get 4.99mm which is a perfect fit, but if that isn't available, I have tested sizes down to 4.95 and they work well. ( https://www.amazon.com/dp/B002710PAU/ref=cm_sw_em_r_mt_dp_U_.aizCb7JR6AEH )
- Go / No-go plug gauges from McMaster Carr, cut to length. Here is one that is 4.97mm. With stated tolerance, this should work (but untested) ( https://www.mcmaster.com/2281a2 )
- All3dmakers sells a 15.8 mm length, 4.95mm diameter dowel pin. This is the perfect length, so no cutting is necessary. ( https://all3dmakers.com/products/bear-x-axis-dowel-pin-for-e3d-gates-5mm-bore-idler )
- 5mm diameter dowel pin (commonly available), turned down to slightly under-sized. To do this, you can chuck the pin in a drill, and use the drill so spin the pin against a piece of fine (~800) grit sandpaper.
For the options you need to cut to length, any length between 15 - 16mm will work.
EDIT (2018-12-26): Added a V2 version of the idler that tightens up spacing to improve strength and to firmly hold the idler by its bearing so that there is zero side-to-side movement. When inserting the idler, you will have to apply some force to insert it. It should click into place, and then spin freely. This version also corrects an issue with the original Bear design that (for me at least) caused bridging issues. Note that I'm leaving the old version up there in case people have issues printing the higher tolerances required for the new part.