Extruder Filament hole diameter vs Hotend

First off, thanks to all for the resource this forum has become. I have gleaned much information.

I finally got my prusa working after coming back to it after 6 months. I was doing the calibration steps, heating up the printbed and hotend however my silly purchasing decisions have once again got me into a tough spot.

The Greg's Hinged Accessible Extruder I have was part of a kit and so the hole in it is for 3mm filament. I decided to buy a j-head 1.75mm 0.35 nozzle hotend. I think you may see where this is going.

I was alerted to the problem when I realized the curve of the filament coming into the extruder would inevitably get stuck on the lip of the PTFE liner in the hotend as the diameters dont match (picture attached). It was only then that I started reading about buckling filament, pressure etc.

Question is can I insert a collar within the extruder to get the size down? perhaps threaded and thread it straight into the hole (using it as a guide)? Find someone to print just the main body of the extruder for me?

Extruder filament hole measured at a diameter of 3.4mm.

Thanks for any advice you can give!

You could thread the hole and use an insert, but I think something like clay or even play doe might work. But don't take my word for it.

Fill it in with ABS slurry, wait for it to cure (a day or two) and drill it out? That is, if the wade's extruder you purchased was printed in ABS. (I can't tell from the image)

I am pretty sure the part is PLA, however the idea of putty, epoxy or that sort of material formed around a 2mm (for wiggle room) round object would give me the hole needed. Any idea of material and/or process?

I run a piece of 2mm I.D. brass tubing and super glue it in place. I would imagine just about any material with a 2mm I.D. would work, maybe the empty part of an ink tube from a pen?

A pen ink tube is to narrow, at least a standard BIC was. Where did you source the brass tube? does it fit snugly or is the super glue helping it stay in the centre of the hole?

I know I have seen some ink pens with a bigger ink tube than a BIC. I got a bag of assorted brass scrap from a hobby store. 3mm O.D. 2mm I.D. If you are in the US, a Do-It-Center type hardware store sells hobby brass tube and sheet.

I have my brass about 4 mm extended into the thermal barrier to help guide the filament and align the hot end. It was a slip fit into the extruder, but I glued it so that when doing hot end maintenance the brass would not push up when re-installing the hot end.

Just as an update for other newbies, I bought some aluminum tube from a hobby shop that had a OD of 3mm and a ID of 2.25 (they had nothing narrower.) I had the length long enough to stick out of the bottom of the extruder body to mate directly with a Jhead on a aluminum groovemount plate. Worked fine on the first extrusions I have done so far but time will tell.

Thanks for your advice all!