Clogged bolts. Left, three bolts, some homemade, with sharp teeth that clog after a couple of hours and stop extruding. A world of pain. Right, a bolt (from learcnc on ebay) that extrudes all day every day. Utopia. The issue is microscopic so you just have to make 'em and buy 'em till one works.
Just a guess without seeing them, but do the 3 on the left have straight material for the teeth or is it hooked one way or the other that causes them to peel away material as they turn. (either by the hobbing process loading them in one direction causing curl on the teeth, or possibly burs ) ?
M5 works well for me, too. The material seems to have a rather large influence on long-time performance, too - stainless steel is harder and therefore doesn’t have issues with bent teeth. The right one looks like stainless steel, are your DIY ones stainless as well?
No one ever told me how important this one was… I fought “clogged extruder tips” over and over and over… …until I found out it was a slipping hob instead. I put a proper amount of time in fabricating one to the correct dimensions (radius, depth) and never had a problem again. --The importance of this little curved notch should be in big red letters on all instructions everywhere.
M8 bolts. I printed a small holder with bearings and cut them on a simple mill. The larger the cutter the easier it is. At first i thought M8 threads would be to large, but it is more important to have a clean sharp edge than to have dense cuts.