I've bought a runout sensor compatible with Ender 3 V2 machines, and noticed that after some time they get really squeaky on repeated swift retractions.
Something about the surface of the brass inserts being used up and/or heating from the filament I'm assuming.

Either way, it got really annoying to me, so I decided to make a replacement that I could use which would be easy to print and fix my squeaking issues!

So of course, PTFE tubes came to mind. Excellent glide on those things.

A few things to know: 

• You need M3 threaded inserts to screw the actual sensor into. (You can try to glue it, I guess…) I personally get mine on Ali Express, but any retailer will do. The important part is that you have something like a soldering iron to press them into place.

• I personally use M3 Hex Socket Head Bolts for my screws, which is why my model has holes to countersink them in. The default screws also work with this model, they just will stick out a bit more on the underside of the attachment plate.

• I highly suggest using an M4 drill bit to clean up the PTFE tube through-hole, since the printing orientation and settings will result in imperfections in the sizing. We're trying to pressure-fit it inside, not destroy the tube.

• I personally use a Dremel bit to cut an opening groove into the PTFE tube, but you can fiddle with a sharp blade. Or just use two PTFE tube pieces, one from each side. The world is your oyster!

Instructions:

1. Verify that my models are compatible with your sensor mounting solution. (Dimensions at the end of this description)

2. Print the model(s).

3. Get two M3 threaded inserts and press them in place on the inside with a soldering iron.

   

4. Clean up the PTFE through-hole with an M4 drill bit

   

5. Pressure-fit the PTFE tube(s) in place and cut off excess. (If you wish to use two separate pieces to avoid a mess, skip to step 9)                                      

   

6. Get yourself a Dremel tool and start carving a groove into the PTFE tubing for the filament detection. Please wear a facemask and eye protection while turning plastic to dust. (You can skip to step 7 if you have a super sharp, super thin blade. I use a scalpel.)   

   

7. Clean up the groove with a sharp blade.                                       

   

8. Pass filament through from each side to catch any remaining debris and scrape again.

9. Screw the runout sensor in place.                                                          

   

10. Mount the sensor on your 3D Printer.                                          

    

11. Plug the sensor in and enjoy.                                         

    

Also, the second file is identical except for a name being sunk into the side.

This comes from a joke I've made with a friend who clearly enjoys pareidolia, because she saw an anxious face on the inside of the sensor case. 

So since I can never un-see said face, I decided to embrace it and call the sensor Jimmy. He watches over my filament now, and anxiously makes sure that it is nice and safe.

If you need specific variations on the design, feel free to tell me.

I won't promise to do it swiftly or just edit any minute changes at once, but when the desire to do 3D modeling strikes I'll probably get you what you need, so long as you're clear with your desires and have measurements where applicable. :)

I have included a whole host of measurements in case you wish to re-create and modify this. Just reference me if you do.