A remix of the Ender 3 Filament Roller Guide [http://www.thingiverse.com/thing:3052488] adapted to fit the CR-10 v2. This fits on the stock filament runout sensor shell.
For some reason, only 3 of the 5 parts are showing renderings in the main view, but all 5 parts ARE in the file. I've checked. This is a Thingiverse bug.
Edit: OK, this one (v3 bracket) has truly been fixed properly this time. I just got a new CR-10v2 with which I could do accurate measurements as I was assembling it, instead of trying to lean my head into the enclosure for the other one and take those measurements. The roller now lines up properly with the sensor filament hole.
v4 of the bracket has been uploaded, it now has an observation hole for the filament runout sensor indicator light.
10/6/20: v4.5 now has been uploaded, with the requested beveled/chamfered screw holes. If you are using bevel headed screws use this version. If using socket or flathead screws with or without washers, use v4.0
You will need:
(1) - 608 skateboard bearing
(1) - 5mm x 20mm machine screw
(1) - 5mm machine nut
(2) (+2 optional) 3mm x 20mm machine screws
It will require at least 2 3mm x 20mm machine screws (washers are a plus) to bolt it down. I say "at least" because I only use two out of the 4 screw spots, and leave the other original 2 beveled head ones in place, as they are flush. This allows you to remove the guide if necessary without disturbing the runout sensor. If you do it this way, be sure to choose diagonally opposing corners (either way) for the yours.
As with the original, there are two different guide pulleys of slightly different inside diameters. My bearings use the larger one, but apparently they are not all made the same.
Press the spacer in place on the bearing, insert the 5mm screw through the bracket and spacers/bearing, and secure with a nut on the other side.
4/16/20: I have added a top mounted roller as well, for those that want to move their spool holder to the center of the cross bar. This is offset from the cross bar by approximately half as much as the lower roller is, so that the filament will stay in the roller better. I also added a crosspiece to further retain the filament during retractions and such. This uses the same roller/spacers as the lower guide, so just print two sets of those. There are 4 machine screw holes (use them with 4mm screws and T-nuts), you only really need two of them, the extras are in case you want to move it further out on the bar.