This is a Y carriage belt mount with integrated tensioner for the FolgerTech 2020 i3. It allows the belt to be centered on the bed rather than offset as is the one that comes with the kit. I also wanted to integrate some sort of tensioner and didn't like many of the ones I found that placed the tensioner on the front frame of the printer. For something that rarely needs adjusted I wanted something a bit more subtle and out of the way.
I designed this to use knurled brass inserts (1x M5x7mm, 8x M3x5mm) but plan on creating a version that can use regular nuts when I get a chance and will add it here when I do. I extended the holes past the inserts so that a variety of screw lengths could work and tapered them down so that they would grip the screw like a lock-nut. The inserts were just heat set with a soldering iron.
The tensioner uses an M5 bolt and a length of 20-30mm should work depending on how much travel you want. I'm currently using an M5-0.8 30mm socket cap bolt. You may need to post-process the tensioner block hole so that the screw can more easily rotate within it. I just ran the screw in and out a few times with a drill to loosen it up a bit. The block should rest against the mounting plate enough to keep it from rotating as you tighten/loosen the tensioner screw.
The ridges on the belt mounts fit the GT2 profile well enough to grip it without the need for significant pressure so that stress is limited on the belt and plastic.
Mounting holes: 18mm x 40mm
Underside of plate to belt: 18.5mm
1x M5x7mm knurled insert
8x M3x5mm knurled insert
1x M5 screw (~25-30mm)
8x M3 screws (~8-12mm)
I printed these in Atomic Filament's carbon fiber PETG at 255°C on PEI at 55°C.