Edit: Just noticed the scaling may have been off on either one or both of the 4 and 7 mm bolt STL files. If you downloaded the v02 STLs, please get the v03 models instead. I also added an STL with both the 4 and 7 mm bolts for those wanting to print both at once (for whatever reasons).

An M6 bolt with a funnel shaped hole in it. I made it as a sort of filament tip guide for Anycubic's Metal MK8 Extruder Kit (see photo). It makes threading filament into my printer's bowden tube much less of a struggle. Note the photo is of the "right hand" version of the kit.

If you are still using the stock extruder, try my M6 Nut Funnel Cover - Exruder Filament Guide.

Notes

There are 2 versions, one with 4mm of thread and one with 7mm of thread. Installing the 7mm version will require removing the extruder base plate from the top of the printer (if installed). I made the 4mm version because I had already installed the base plate and didn't want to remove it to install the guide bolt. Installing the 4mm bolt without removing the plate is a little tricky, but it can be done.

This was designed this for use with 1.75mm filaments, it will not work with 2.5 or 3 mm filaments (the hole diameter is close to 2.55mm). Should be printable without supports, I recommend using a small layer height to preserve the threads (I used 0.1mm).